diff --git a/as/k-as.py b/as/k-as.py
index e889bff..45c00c2 100755
--- a/as/k-as.py
+++ b/as/k-as.py
@@ -13,7 +13,7 @@ from collections import OrderedDict
 
 #print("k-as command line: '{}'".format(sys.argv))
 
-WANT_DISASM = True
+WANT_DISASM = False
 
 if len(sys.argv) != 5:
     print("Usage: {} (source file) (memory entry point) (output file) (symbols file)"
@@ -449,8 +449,6 @@ def parse_instr(line):
     else:
         params = None
 
-    fellthrough = False
-
     size = 2
 
     # Byte 2 (rep|lock|0|cond)
@@ -486,6 +484,13 @@ def parse_instr(line):
 
     tok = params.split(',')
 
+    # 'call' special case... temporary
+    if instr_name == 'call':
+        if len(tok) == 2:
+            instr_name = 'xcall2'
+        elif len(tok) == 3:
+            instr_name = 'xcall3'
+
     #
     # Parse operands
     #
@@ -540,8 +545,6 @@ def parse_instr(line):
                 print("Missing access length modifier: {}".format(line))
                 leave(1)
 
-            instr_name += "_m"
-
             # cheap way of getting [reg - imm] to work
             word = word.replace('-', '+ -')
             
@@ -668,7 +671,6 @@ def parse_instr(line):
         # immediates
         if is_number(word):
             n = int(word, base=0)
-            instr_name += "_i"
 
             if n < 0 or n > 0xFFFFFFFF:
                 size += 9
@@ -695,7 +697,6 @@ def parse_instr(line):
         # register
         elif word in pregs:
             size += 1
-            instr_name += "_r"
             instr_args += word
             continue
 
@@ -703,7 +704,6 @@ def parse_instr(line):
         # ModRM + imm
         size += 5
 
-        instr_name += "_i"
         instr_args += "%%imm8 {} ".format(fmts["imm32"])
 
         if word[0] == '.':
diff --git a/ka/crt/fmt/doprnt.k b/ka/crt/fmt/doprnt.k
index b67a4f3..59e2bf6 100644
--- a/ka/crt/fmt/doprnt.k
+++ b/ka/crt/fmt/doprnt.k
@@ -32,10 +32,9 @@ doprnt:
 .print_regular:
     b.z r12, r13, .check_modf
 
-    mov ax0, b[r12]
-    call .doput
+    call .doput, b[r12]
 
-    add r12, r12, 1
+    inc r12, 1
     jmp .print_regular
 
 .check_modf:
@@ -45,7 +44,7 @@ doprnt:
 
     ; we did find a modifier / '%'
     mov rax, b[r12+1]
-    add r12, r12, 2
+    inc r12, 2
 
     b.z rax, 's', .modf_s
     b.z rax, 'c', .modf_c
@@ -62,24 +61,23 @@ doprnt:
 .modf_s:
     ; get string address
     mov r13, q[r14]
-    add r14, r14, 8
+    inc r14, 8
 
-    cmp r13, zero
-    jmp.z .nullstring
+    b.z r13, zero, .nullstring
 
 .print_string:
     mov ax0, b[r13]
-    cmp ax0, zero
-    jmp.z .main_loop
+    b.z ax0, zero, .main_loop
 
-    add r13, r13, 1
+    inc r13, 1
     call .doput
+
     jmp .print_string
 
 .modf_c:
-    mov ax0, q[r14]
-    add r14, r14, 8
-    call .doput
+    call .doput, q[r14]
+    inc r14, 8
+
     jmp .main_loop
 
 .modf_p:
@@ -105,23 +103,21 @@ doprnt:
 
 .print_number:
     ; allocate itoa conversion buffer
-    sub rsp, rsp, 80
+    dec rsp, 80
     mov r13, rsp
 
     ; assume modifier already set up ax2
-    mov ax0, rsp
-    mov ax1, q[r14]
-    call itoa
-    add r14, r14, 8
+    call itoa, rsp, q[r14]
+    inc r14, 8
 
 .print_itoa_buf:
     mov ax0, b[r13]
 
     cmp ax0, zero
-    add.z rsp, rsp, 80
+    inc.z rsp, 80
     jmp.z .main_loop
 
-    add r13, r13, 1
+    inc r13, 1
     call .doput
     jmp .print_itoa_buf
 
@@ -164,7 +160,7 @@ doprnt:
 ;
 .doput:
     ; update print count
-    add r16, r16, 1
+    inc r16, 1
 
     ; if n==0, don't print
     ; we follow the C convention that sprintf()-like functions
@@ -174,7 +170,7 @@ doprnt:
     ret.z
 
     ; if n>0, decrement n and print
-    sub r15, r15, 1
+    dec r15, 1
     call r17
     
     ; did putc fail?
diff --git a/ka/crt/fmt/ltostr.k b/ka/crt/fmt/ltostr.k
index dff2785..0763d44 100644
--- a/ka/crt/fmt/ltostr.k
+++ b/ka/crt/fmt/ltostr.k
@@ -44,15 +44,15 @@ ltostr:
 
     b.a rdx, 9, .nondec      ; rdx > 9 ?
 
-    add rdx, rdx, '0'
+    inc rdx, '0'
     jmp .next
 
 .nondec:
-    add rdx, rdx, 55     ; 'A' - 10
+    inc rdx, 55     ; 'A' - 10
 
 .next:
     mov b[ax0], rdx
-    add ax0, ax0, 1
+    inc ax0, 1
 
     div ax1, ax1, ax2
     jmp .conv
diff --git a/ka/crt/fmt/strtol.k b/ka/crt/fmt/strtol.k
index 508502e..487bb8d 100644
--- a/ka/crt/fmt/strtol.k
+++ b/ka/crt/fmt/strtol.k
@@ -39,12 +39,12 @@ strtoq:
 
 .skip_spc:
     cmp b[rdx], ' '
-    add.z rdx, rdx, 1
+    inc.z rdx, 1
     jmp.z .skip_spc
 
     ; skip +
     cmp b[rdx], '+'
-    add.z rdx, rdx, 1
+    inc.z rdx, 1
 
     ; signed?
     cmp ax2, zero
@@ -53,7 +53,7 @@ strtoq:
 
     ; parse '-'
     cmp b[rdx], '-'
-    add.z rdx, rdx, 1
+    inc.z rdx, 1
     mov.z rsi, 1
     mov.nz rsi, zero
 
@@ -64,7 +64,7 @@ strtoq:
     ; base prefix?
     b.nz b[rdx], '0', .main_loop
 
-    add rdx, rdx, 1
+    inc rdx, 1
     movzx rcx, b[rdx]
 
     ; "0x"/"0b" prefix
@@ -81,7 +81,7 @@ strtoq:
     ; if not, leave rax = 0 and *rdx = 'x'
     b.nz ax1, 16, .done
     ; else
-    add rdx, rdx, 1
+    inc rdx, 1
     jmp .main_loop
 
 .parsed_0b:
@@ -89,7 +89,7 @@ strtoq:
     ; if not, leave rax = 0 and *rdx = 'b'
     b.nz ax1, 2, .done
     ; else
-    add rdx, rdx, 1
+    inc rdx, 1
     jmp .main_loop
 
 .base_0:
@@ -98,15 +98,15 @@ strtoq:
     cmp b[rdx], '0'
     mov.nz ax1, 10
     jmp.nz .main_loop
-    add rdx, rdx, 1
+    inc rdx, 1
 
     cmp b[rdx], 'x'
-    add.z rdx, rdx, 1
+    inc.z rdx, 1
     mov.z ax1, 16
     jmp.z .main_loop
 
     cmp b[rdx], 'b'
-    add.z rdx, rdx, 1
+    inc.z rdx, 1
     mov.z ax1, 2
     jmp.z .main_loop
 
@@ -114,23 +114,23 @@ strtoq:
 
 .main_loop:
     movzx rcx, b[rdx]
-    add rdx, rdx, 1
+    inc rdx, 1
 
     cmp rcx, '0'
     jmp.b .done
     cmp.ae rcx, '9'
-    sub.be rcx, rcx, '0'
+    dec.be rcx, '0'
     jmp.be .next
 
     cmp rcx, 'A'
     cmp.ae rcx, 'Z'
-    sub.be rcx, rcx, 55  ; 'A' - 10
+    dec.be rcx, 55  ; 'A' - 10
     jmp.be .next
 
     cmp rcx, 'a'
     jmp.b .next
     cmp.ae rcx, 'z'
-    sub.be rcx, rcx, 87 ; 'a' - 10
+    dec.be rcx, 87 ; 'a' - 10
     jmp.be .next
 
 .next:
@@ -138,7 +138,7 @@ strtoq:
     b.ae rcx, ax1, .done
 
     mul rax, rax, ax1
-    add rax, rax, rcx
+    inc rax, rcx
     jmp .main_loop
 
 .done:
diff --git a/ka/crt/lib/time.k b/ka/crt/lib/time.k
index bed77ef..9c6ac2c 100644
--- a/ka/crt/lib/time.k
+++ b/ka/crt/lib/time.k
@@ -36,7 +36,7 @@ DaysInYear:
     jmp.cxnz .end
 
 .leap:
-    add rax, rax, 1
+    inc rax, 1
 
 .end:
     ret
diff --git a/ka/crt/mem/memcpy.k b/ka/crt/mem/memcpy.k
index f5e30e1..9056b37 100644
--- a/ka/crt/mem/memcpy.k
+++ b/ka/crt/mem/memcpy.k
@@ -10,11 +10,7 @@ memcpy:
 
 .l:
     sub rdx, ax2, rcx
-
-    mov rax, b[ax1+rdx]
-    mov b[ax0+rdx], rax
-
+    mov b[ax0+rdx], b[ax1+rdx]
     loop .l
-
     ret
 
diff --git a/ka/crt/str/strcmp.k b/ka/crt/str/strcmp.k
index edf4eff..a148b13 100644
--- a/ka/crt/str/strcmp.k
+++ b/ka/crt/str/strcmp.k
@@ -22,11 +22,11 @@ strcmp:
     add rbx, rax, rdx
     jmp.bxz .r
 
-    add rcx, rcx, 1
+    inc rcx, 1
     jmp .l
 
 .r:
-    sub rax, rax, rdx
+    dec rax, rdx
     ret
 
 ;
@@ -43,11 +43,11 @@ strncmp:
     cmp rax, rdx
     jmp.nz .r
 
-    add ax0, ax0, 1
-    add ax1, ax1, 1
+    inc ax0, 1
+    inc ax1, 1
     loop .l
 
 .r:
-    sub rax, rax, rdx
+    dec rax, rdx
     ret
 
diff --git a/ka/crt/str/strcpy.k b/ka/crt/str/strcpy.k
index 67ebcc2..d15d34f 100644
--- a/ka/crt/str/strcpy.k
+++ b/ka/crt/str/strcpy.k
@@ -11,8 +11,8 @@ strcpy:
 
     ret.cxz
 
-    add ax0, ax0, 1
-    add ax1, ax1, 1
+    inc ax0, 1
+    inc ax1, 1
 
     jmp .l
 
@@ -24,11 +24,10 @@ strncpy:
     ret.cxz
 
 .l:
-    mov rax, b[ax1]
-    mov b[ax0], rax
+    mov b[ax0], b[ax1]
 
-    add ax0, ax0, 1
-    add ax1, ax1, 1
+    inc ax0, 1
+    inc ax1, 1
 
     loop .l
     ret
@@ -46,8 +45,8 @@ strnzcpy:
 
     jmp.axz .r
 
-    add ax0, ax0, 1
-    add ax1, ax1, 1
+    inc ax0, 1
+    inc ax1, 1
 
     loop .l
 
diff --git a/ka/crt/str/strrev.k b/ka/crt/str/strrev.k
index 89752d3..9911319 100644
--- a/ka/crt/str/strrev.k
+++ b/ka/crt/str/strrev.k
@@ -18,20 +18,19 @@ strrev:
     ; the null terminator
     mov rcx, STRLEN_MAX
     scasb.rep.nz ax1, zero
-    sub ax1, ax1, 1
+    dec ax1, 1
 
 .2:
     ; copy, going backward though str
     ; and forward through buf
-    mov rax, b[ax1]
-    mov b[ax0], rax
+    mov b[ax0], b[ax1]
 
     cmp ax1, rsi
     mov.z b[ax0+1], zero
     ret.z
 
-    add ax0, ax0, 1
-    sub ax1, ax1, 1
+    inc ax0, 1
+    dec ax1, 1
     jmp .2
 
 
@@ -50,18 +49,16 @@ strrev2:
     ; the null terminator
     mov rcx, STRLEN_MAX
     scasb.rep.nz ax1, zero
-    sub ax1, ax1, 1
+    dec ax1, 1
 
     ; increase ax0 while decreasing ax1, performing exchanges
 .2:
     b.ae ax0, ax1, .3
 
-    mov rax, b[ax1]
-    xchg rax, b[ax0]
-    mov b[ax1], rax
+    xchg b[ax0], b[ax1]
 
-    add ax0, ax0, 1
-    sub ax1, ax1, 1
+    inc ax0, 1
+    dec ax1, 1
     jmp .2
 
 .3:
diff --git a/ka/sys/intr/common.k b/ka/sys/intr/common.k
index 8e48c30..28aecc1 100644
--- a/ka/sys/intr/common.k
+++ b/ka/sys/intr/common.k
@@ -5,9 +5,7 @@ TrapHandlers.prolog:
     mov rbp, rsp
 
     ; nx0 = caller's cr2
-    mov ax0, r14
-    mov ax1, $cr2
-    call RFS.LoadReg
+    call RFS.LoadReg, r14, $cr2
 
     ; we don't preserve the r12 we got
     mov r12, rax
diff --git a/ka/sys/intr/trap0.k b/ka/sys/intr/trap0.k
index f4f60cb..9e5f45b 100644
--- a/ka/sys/intr/trap0.k
+++ b/ka/sys/intr/trap0.k
@@ -9,10 +9,8 @@ trap0_handler:
     jmp TrapHandlers.prolog
 
 .text:
-    mov ax0, r14
-    mov ax1, $rax
-    call RFS.LoadReg
-    call RFS.LoadArgs
+    call RFS.LoadReg, r14, $rax
+    call RFS.LoadArgs, r14
 
     b.z rax, zero, .handle_Shutdown
     b.z rax, Sys.Exit, .handle_Exit
@@ -66,7 +64,7 @@ trap0_handler:
     call RFS.StoreReg, zero, $cr0
 
     mov rcx, CMDCOM_LOADP
-    sub rcx, rcx, 0x100000
+    dec rcx, 0x100000
 
     ; Code offset
     mov ax2, rcx
@@ -87,17 +85,17 @@ trap0_handler:
 ; Disk API
 ;
 .handle_FindFirst:
-    add ax0, ax0, r12
+    inc ax0, r12
     call DISK.FindFirst
     jmp .fini
 
 .handle_FindNext:
-    add ax0, ax0, r12
+    inc ax0, r12
     call DISK.FindNext
     jmp .fini
 
 .handle_OpenFile:
-    add ax0, ax0, r12
+    inc ax0, r12
     call DISK.OpenFile
     jmp .fini
 
@@ -106,7 +104,7 @@ trap0_handler:
     jmp .fini
 
 .handle_ReadFile:
-    add ax1, ax1, r12
+    inc ax1, r12
     call DISK.ReadFile
     jmp .fini
 
diff --git a/ka/sys/main.k b/ka/sys/main.k
index 31f4f1d..c931f68 100644
--- a/ka/sys/main.k
+++ b/ka/sys/main.k
@@ -21,7 +21,7 @@ InitSyscalls:
     call RFS.StoreReg
     
     mov ax1, ax0
-    add ax0, ax0, 255    # TRAP no. (ax0 - 1)
+    inc ax0, 255    # TRAP no. (ax0 - 1)
     call IDT.AddHandler
 
     ret
diff --git a/ka/usr/cmd/dir.k b/ka/usr/cmd/dir.k
index 854a6cb..45440c3 100644
--- a/ka/usr/cmd/dir.k
+++ b/ka/usr/cmd/dir.k
@@ -10,9 +10,7 @@ builtins.dir:
     push r12
     mov r12, zero        # no. of files found
 
-    mov rcx, STRLEN_MAX
-    mov rdx, .dirmsg
-    prns.rep.nz rdx
+    call print, .dirmsg
 
 .dirmsg = "Directory of C:\\\n\n"
 
@@ -34,7 +32,7 @@ builtins.dir:
     jmp.axz .end
 
     ; found something
-    add r12, r12, 1
+    inc r12, 1
 
     ; separate extension from file name
     mov rcx, NAME_MAX
@@ -48,13 +46,13 @@ builtins.dir:
 
     ; calculate where to put extension
     sub rdi, rsi, .buf
-    sub rdi, rdi, 1
+    dec rdi, 1
 
 .ext_pad:
     ; print at least 11 non-space characters before extension
     b.ae rdi, 11, .print_ext
     prn ' '
-    add rdi, rdi, 1
+    inc rdi, 1
     jmp .ext_pad
 
 .print_ext:
@@ -69,10 +67,9 @@ builtins.dir:
     b.z b[rsi], 0, .print_ext.2
 
     ; print and decrease rcx, unless it's already 0
-    mov rbx, b[rsi]
-    prn rbx
-    add rsi, rsi, 1
-    sub.cxnz rcx, rcx, 1
+    prn b[rsi]
+    inc rsi, 1
+    dec.cxnz rcx, 1
 
     jmp .print_ext.1
 
@@ -84,9 +81,8 @@ builtins.dir:
 
 .print_bytes:
     ; print file size in bytes
-    prn ' '
-    prn ' '
-    prn ' '
+    mov rcx, 3
+    prn.rep ' '
 
     shr rax, rdx, 10
     and rdx, rdx, 1023
@@ -94,7 +90,7 @@ builtins.dir:
     push rdx
     push rax
     call printf, .bytesstr
-    add rsp, rsp, 16
+    inc rsp, 16
 
 .bytesstr = "%d kilobytes + %d bytes"
 
@@ -106,7 +102,7 @@ builtins.dir:
 .end:
     push r12
     call printf, .endstr1
-    add rsp, rsp, 8
+    inc rsp, 8
 
     call print, .endstr2
 
diff --git a/ka/usr/cmd/main.k b/ka/usr/cmd/main.k
index 18bd01f..934a10d 100644
--- a/ka/usr/cmd/main.k
+++ b/ka/usr/cmd/main.k
@@ -41,7 +41,7 @@ main:
     jmp.cxz .input_loop     ; no
 
     ; yes, delete it
-    sub rcx, rcx, 1
+    dec rcx, 1
     add rdx, rcx, argbuf
     mov b[rdx], zero
 
@@ -63,7 +63,7 @@ main:
     ; add character to buffer and increase iterator (rcx)
     add rdx, rcx, argbuf
     mov b[rdx], rax
-    add rcx, rcx, 1
+    inc rcx, 1
 
     ; another one
     jmp .input_loop
@@ -87,7 +87,7 @@ main:
 
     ; skip spaces
     cmp rcx, ' '
-    add.z rsi, rsi, 1
+    inc.z rsi, 1
     jmp.z .next_space
 
     ; if we're here, we found a
@@ -105,17 +105,16 @@ main:
     ; how much do we copy?
     sub rcx, rdx, argbuf
     jmp.cxz .detect_builtin
-    sub rcx, rcx, 1
+    dec rcx, 1
 
     mov rdi, argbuf
     mov rsi, argv0
 
 .copy_loop:
-    mov rax, b[rdi]
-    mov b[rsi], rax
+    mov b[rsi], b[rdi]
 
-    add rdi, rdi, 1
-    add rsi, rsi, 1
+    inc rdi, 1
+    inc rsi, 1
 
     loop .copy_loop
 
@@ -185,7 +184,7 @@ main:
 
     call printf, .datefmt
 
-    add rsp, rsp, 40
+    inc rsp, 40
 
     jmp .print_prompt
 
@@ -255,7 +254,7 @@ main:
     push b[rax+1]
     push b[rax+2]
     call printf, .timefmt
-    add rsp, rsp, 24
+    inc rsp, 24
 
     jmp .print_prompt
 
@@ -307,7 +306,7 @@ main:
     push q[argv1pos]
     push argv0
     call printf, .fnf_errmsg
-    add rsp, rsp, 16
+    inc rsp, 16
 
     jmp .print_prompt
 
@@ -317,7 +316,7 @@ main:
     push q[argv1pos]
     push argv0
     call printf, .ef_errmsg
-    add rsp, rsp, 16
+    inc rsp, 16
 
     jmp .print_prompt
 
@@ -327,7 +326,7 @@ main:
     push q[argv1pos]
     push argv0
     call printf, .cno_errmsg
-    add rsp, rsp, 16
+    inc rsp, 16
 
     jmp .print_prompt
 
diff --git a/vm/in/ALU b/vm/in/ALU
index 765eacc..6553ccc 100644
--- a/vm/in/ALU
+++ b/vm/in/ALU
@@ -12,7 +12,7 @@
 #
 # Preserves all flags
 #
-or r r ri
+or 3
 
 #
 # Bitwise AND operation
@@ -21,7 +21,7 @@ or r r ri
 #
 # Preserves all flags
 #
-and r r ri
+and 3
 
 #
 # Bitwise XOR operation
@@ -30,7 +30,7 @@ and r r ri
 #
 # Preserves all flags
 #
-xor r r ri
+xor 3
 
 #
 # Logical left/right shift (SHL/SHR)
@@ -40,8 +40,8 @@ xor r r ri
 #
 # Preserves all flags
 #
-shl r r ri
-shr r r ri
+shl 3
+shr 3
 
 #
 # Arithmetical left/right shift (SAL/SAR)
@@ -51,8 +51,8 @@ shr r r ri
 #
 # Preserves all flags
 #
-sal r r ri
-sar r r ri
+sal 3
+sar 3
 
 #---------------------------------------------------------------------------#
 # Arithmetic instructions                                                   #
@@ -67,8 +67,7 @@ sar r r ri
 # Sets OF is signed integer overflow occur, clears it otherwise
 # Sets ZF and SF according to the result
 #
-cmp r ri
-cmp m ri
+cmp 2
 
 #
 # Arithmetical ADD operation
@@ -79,8 +78,9 @@ cmp m ri
 # Sets OF is signed integer overflow occur, clears it otherwise
 # Sets ZF and SF according to the result
 #
-add r r ri
-addf r r ri
+inc 2
+add 3
+addf 3
 
 #
 # Arithmetical SUB operation
@@ -91,8 +91,9 @@ addf r r ri
 # Sets OF is signed integer overflow occur, clears it otherwise
 # Sets ZF and SF according to the result
 #
-sub r r ri
-subf r r ri
+dec 2
+sub 3
+subf 3
 
 #
 # Arithmetical ADD/SUB operation, with carry/overflow
@@ -104,8 +105,8 @@ subf r r ri
 # Sets OF is signed integer overflow occur, clears it otherwise
 # Sets ZF and SF according to the result
 #
-adcx r r ri
-sbbx r r ri
+adcx 3
+sbbx 3
 
 #
 # Arithmetical MUL operation
@@ -115,8 +116,8 @@ sbbx r r ri
 # Preserves ZF and SF
 # Sets CF and OF if HI($src1 * $src2) > 0, clears them otherwise
 #
-mul r r ri
-mulf r r ri
+mul 3
+mulf 3
 
 # Arithmetical unsigned MUL operation
 #
@@ -125,7 +126,7 @@ mulf r r ri
 #
 # Preserves all flags
 #
-mulhi r r ri
+mulhi 3
 
 # Arithmetical signed MUL operation
 #
@@ -134,7 +135,7 @@ mulhi r r ri
 #
 # Preserves all flags
 #
-imulhi r r ri
+imulhi 3
 
 #
 # Arithmetical unsigned DIV operation
@@ -143,7 +144,7 @@ imulhi r r ri
 #
 # Preserves all flags
 #
-div r r ri
+div 3
 
 #
 # Arithmetical signed DIV operation
@@ -152,7 +153,7 @@ div r r ri
 #
 # Preserves all flags
 #
-idiv r r ri
+idiv 3
 
 #
 # Arithmetical modulo operation (REM)
@@ -161,5 +162,5 @@ idiv r r ri
 #
 # Preserves all flags
 #
-rem r r ri
+rem 3
 
diff --git a/vm/in/MEM b/vm/in/MEM
index b5bc40e..05779f8 100644
--- a/vm/in/MEM
+++ b/vm/in/MEM
@@ -10,7 +10,7 @@
 #
 #       RIP = $1
 #
-jmp ri
+jmp 1
 
 #
 # RCX-dependent jump (LOOP) instruction
@@ -20,7 +20,7 @@ jmp ri
 #           RIP = $1
 #       FI  
 #
-loop ri
+loop 1
 
 #
 # Conditional absolute jumps (B)
@@ -38,7 +38,7 @@ loop ri
 #
 # Suffixing B with the REP suffix results in undefined behavior
 #
-b rm ri ri
+b 3
 
 
 #---------------------------------------------------------------------------#
@@ -51,9 +51,9 @@ b rm ri ri
 #       PUSH(RIP)
 #       JMP(RIP)
 #
-call ri
-call i ri
-call i ri ri
+call 1
+xcall2 2
+xcall3 3
 
 #
 # Return to caller (RET)
@@ -69,7 +69,7 @@ ret
 #       RBP = RSP
 #       RSP = RSP - $1
 #
-enter i
+enter 1
 
 #
 # Leave stack frame (LEAVE)
@@ -85,7 +85,7 @@ leave
 #       RSP = RSP - 8
 #       *RSP = $1
 #
-push rim
+push 1
 
 #
 # POP value from stack
@@ -93,7 +93,7 @@ push rim
 #       $1 = *RSP
 #       RSP = RSP + 8
 #
-pop r
+pop 1
 
 #---------------------------------------------------------------------------#
 # Movement instructions                                                     #
@@ -111,31 +111,30 @@ pop r
 #
 # Preserves all flags
 #
-lea r m
+lea 2
 
 #
 # Move data (MOV) instruction
 #
 #       $1 = SignExtend($2)
 #
-mov r rim
-mov m ri
+mov 2
 
 #
 # Load from memory with zero-extension (MOVSX/MOVZX) instruction
 #
 #       $1 = ZeroExtend($2)
 #
-movzx r m
+movzx 2
 
 #
 # Move with sign-extension (MOVSXx) instruction
 #
 #       $1 = SignExtend($2 & (2^(8 * sizeof(x)) - 1)
 #
-movsxb r r
-movsxw r r
-movsxd r r
+movsxb 2
+movsxw 2
+movsxd 2
 
 #
 # Exchange (XCHG) instruction
@@ -144,5 +143,5 @@ movsxd r r
 #       $1 = $2
 #       $2 = $_
 #
-xchg r rm
+xchg 2
 
diff --git a/vm/in/MISC b/vm/in/MISC
index 7397baf..f4d3760 100644
--- a/vm/in/MISC
+++ b/vm/in/MISC
@@ -38,14 +38,14 @@ into
 #
 # Get timestamp in µseconds
 #
-utime r r
+utime 2
 
 #
 # $1 = seconds since start of month
 # $2 = current month
 # $3 = current year
 #
-ytime r r r
+ytime 3
 
 #
 # Clear all GPR registers except RBP/RSP
@@ -61,9 +61,9 @@ cls
 #
 # Change endianness
 #
-bswap r r
-wswap r r
-dswap r r
+bswap 2
+wswap 2
+dswap 2
 
 #---------------------------------------------------------------------------#
 # I/O instructions                                                          #
@@ -72,7 +72,7 @@ dswap r r
 #
 # Send a character to standard output (PRN)
 #
-prn ri
+prn 1
 
 #
 # Print a string to standard output (PRN)
@@ -89,10 +89,10 @@ prn ri
 #       FI
 #       
 #
-prns r
+prns 1
 
 #
 # Scan a character from standard input (SCAN)
 #
-scan r
+scan 1
 
diff --git a/vm/in/STRING b/vm/in/STRING
index f2f7be0..beef788 100644
--- a/vm/in/STRING
+++ b/vm/in/STRING
@@ -15,10 +15,10 @@
 #           %str = %str - sizeof(x)
 #       FI
 #
-stosb r ri
-stosw r ri
-stosd r ri
-stosq r ri
+stosb 2
+stosw 2
+stosd 2
+stosq 2
 
 #
 # Scan string for a particular value (SCASx)
@@ -42,10 +42,10 @@ stosq r ri
 # - Does not move past the value when found
 # - 'SCASB.REP.NZ reg ch' is a short 'strchnul()'
 #
-scasb r ri
-scasw r ri
-scasd r ri
-scasq r ri
+scasb 2
+scasw 2
+scasd 2
+scasq 2
 
 #---------------------------------------------------------------------------#
 
diff --git a/vm/in/SUPER b/vm/in/SUPER
index 4197855..c78f8b3 100644
--- a/vm/in/SUPER
+++ b/vm/in/SUPER
@@ -48,7 +48,7 @@ hlt
 #       #ILL if $1 > 255
 #       #($1+256) otherwise
 #
-trap ri
+trap 1
 
 #
 # Return from exception/interrupt (IRET)
@@ -79,7 +79,7 @@ sti
 # Throws:
 #       #SYS if not in supervisor mode
 #
-devctl r r
+devctl 2
 
 #
 # Call a device-defined function slot of device (IOCALL)
@@ -89,5 +89,5 @@ devctl r r
 # Throws:
 #       #SYS if not in supervisor mode
 #
-iocall ri ri
+iocall 2
 
diff --git a/vm/in/alu.c b/vm/in/alu.c
index cd5cd8c..a99d5da 100644
--- a/vm/in/alu.c
+++ b/vm/in/alu.c
@@ -8,27 +8,32 @@
 
 //----------------------------------------------------------------------------//
 
-IMPL_START(or) { *r1 = p2->val | p3->val; return 1; }
-IMPL_START(and) { *r1 = p2->val & p3->val; return 1; }
-IMPL_START(xor) { *r1 = p2->val ^ p3->val; return 1; }
+IMPL_START(or) { SRCP(p2); SRCP(p3); *r1 = p2->val | p3->val; return 1; }
+IMPL_START(and) { SRCP(p2); SRCP(p3); *r1 = p2->val & p3->val; return 1; }
+IMPL_START(xor) { SRCP(p2); SRCP(p3); *r1 = p2->val ^ p3->val; return 1; }
 
 //----------------------------------------------------------------------------//
 
-IMPL_START(shl) { *r1 = p2->val << p3->val; return 1; }
-IMPL_START(shr) { *r1 = p2->val >> p3->val; return 1; }
-IMPL_START(sal) { *r1 = (ulong)((long)p2->val << (long)p3->val); return 1; }
-IMPL_START(sar) { *r1 = (ulong)((long)p2->val >> (long)p3->val); return 1; }
+IMPL_START(shl) { SRCP(p2); SRCP(p3); *r1 = p2->val << p3->val; return 1; }
+IMPL_START(shr) { SRCP(p2); SRCP(p3); *r1 = p2->val >> p3->val; return 1; }
+IMPL_START(sal) { SRCP(p2); SRCP(p3); *r1 = (ulong)((long)p2->val << (long)p3->val); return 1; }
+IMPL_START(sar) { SRCP(p2); SRCP(p3); *r1 = (ulong)((long)p2->val >> (long)p3->val); return 1; }
 
 //----------------------------------------------------------------------------//
 
-IMPL_START(add) { *r1 = p2->val + p3->val; return 1; }
-IMPL_START(addf) { COMPARE_ADD(p2->val, p3->val); *r1 = p2->val + p3->val; return 1; }
+IMPL_START(inc) { SRCP(p1); SRCP(p2); *r1 = p1->val + p2->val; return 1; }
+IMPL_START(add) { SRCP(p2); SRCP(p3); *r1 = p2->val + p3->val; return 1; }
+IMPL_START(addf) { SRCP(p2); SRCP(p3); COMPARE_ADD(p2->val, p3->val); *r1 = p2->val + p3->val; return 1; }
 
-IMPL_START(sub) { *r1 = p2->val - p3->val; return 1; }
-IMPL_START(subf) { COMPARE_SUB(p2->val, p3->val); *r1 = p2->val - p3->val; return 1; }
+IMPL_START(dec) { SRCP(p1); SRCP(p2); *r1 = p1->val - p2->val; return 1; }
+IMPL_START(sub) { SRCP(p2); SRCP(p3); *r1 = p2->val - p3->val; return 1; }
+IMPL_START(subf) { SRCP(p2); SRCP(p3); COMPARE_SUB(p2->val, p3->val); *r1 = p2->val - p3->val; return 1; }
 
 IMPL_START(adcx)
 {
+    SRCP(p2);
+    SRCP(p3);
+
     p3->val += !!(R(RFX)&CF);
     COMPARE_ADD(p2->val, p3->val);
     *r1 = p2->val + p3->val;
@@ -38,6 +43,9 @@ IMPL_START(adcx)
 
 IMPL_START(sbbx)
 {
+    SRCP(p2);
+    SRCP(p3);
+
     p3->val += !!(R(RFX)&CF); 
     COMPARE_SUB(p2->val, p3->val);
     *r1 = p2->val - p3->val;
@@ -47,11 +55,14 @@ IMPL_START(sbbx)
 
 //----------------------------------------------------------------------------//
 
-IMPL_START(mul) { *r1 = p2->val * p3->val; return 1; }
-IMPL_START(rem) { *r1 = p2->val % p3->val; return 1; }
+IMPL_START(mul) { SRCP(p2); SRCP(p3); *r1 = p2->val * p3->val; return 1; }
+IMPL_START(rem) { SRCP(p2); SRCP(p3); *r1 = p2->val % p3->val; return 1; }
 
 IMPL_START(div)
 {
+    SRCP(p2);
+    SRCP(p3);
+
     if (!p3->val)
         _except(ctx, E_DIV, "DIV by 0");
     *r1 = p2->val / p3->val;
@@ -61,6 +72,9 @@ IMPL_START(div)
 
 IMPL_START(idiv)
 {
+    SRCP(p2);
+    SRCP(p3);
+
     if (!p3->val)
         _except(ctx, E_DIV, "IDIV by 0");
 
@@ -81,12 +95,18 @@ static void __unsigned_multiply128(ulong u, ulong v, ulong *hi, ulong *lo)
 
 IMPL_START(mulhi)
 {
+    SRCP(p2);
+    SRCP(p3);
+
     __unsigned_multiply128(p2->val, p3->val, r1, r2);
     return 2;
 }
 
 IMPL_START(mulf)
 {
+    SRCP(p2);
+    SRCP(p3);
+
     ulong tmp;
     __unsigned_multiply128(p2->val, p3->val, &tmp, r1);
     R(RFX) = p2->val ? (R(RFX)|CF|OF) : R(RFX)&~(CF|OF);
@@ -106,6 +126,9 @@ static void __signed_multiply128(ulong u, ulong v, ulong *hi, ulong *lo)
 
 IMPL_START(imulhi)
 {
+    SRCP(p2);
+    SRCP(p3);
+
     __signed_multiply128(p2->val, p3->val, r1, r2);
     return 2;
 }
diff --git a/vm/in/arch_i.py b/vm/in/arch_i.py
index 15f6126..b4f0e7e 100644
--- a/vm/in/arch_i.py
+++ b/vm/in/arch_i.py
@@ -5,25 +5,6 @@
 
 from tempfile import TemporaryFile
 
-def getflag(s):
-    if s == "r":
-        return "P_REG"
-
-    if s == "i":
-        return "P_IMM"
-
-    if s == "m":
-        return "P_MEM"
-
-    return "__FLAG_ERROR__"
-
-def doprnt(fp, i, p1, p2, p3):
-    for c1 in p1:
-        for c2 in p2:
-            for c3 in p3:
-                fp.write("{} {} {} {}".format(i, c1, c2, c3).strip())
-                fp.write('\n')
-
 def parse_1(fi, fp):
     global count
 
@@ -41,36 +22,7 @@ def parse_1(fi, fp):
             parse_1(fi2, fp)
             continue
 
-        tok = line.split()
-
-        if len(tok) == 0:
-            continue
-
-        i = tok[0]
-
-        if len(tok) == 1:
-            doprnt(fp, i, ' ', ' ', ' ')
-            continue
-
-        if len(tok) == 2:
-            p = tok[1]
-            doprnt(fp, i, p, ' ', ' ')
-            continue
-
-        if len(tok) == 3:
-            p1 = tok[1]
-            p2 = tok[2]
-            doprnt(fp, i, p1, p2, ' ')
-            continue
-
-        assert(len(tok) == 4)
-        p1 = tok[1]
-        p2 = tok[2]
-        p3 = tok[3]
-
-        doprnt(fp, i, p1, p2, p3)
-
-    fi.close()
+        fp.write("{}\n".format(line))
 
 def parse_2(fp):
     global count
@@ -89,41 +41,19 @@ def parse_2(fp):
 
         if len(tok) == 1:
             name = tok[0]
-            p1 = "NOPRM"
-            p2 = "NOPRM"
-            p3 = "NOPRM"
-
-        elif len(tok) == 2:
-            name = "{}_{}".format(tok[0], tok[1])
-            p1 = getflag(tok[1])
-            p2 = "NOPRM"
-            p3 = "NOPRM"
-
-        elif len(tok) == 3:
-            name = "{}_{}_{}".format(tok[0], tok[1], tok[2])
-            p1 = getflag(tok[1])
-            p2 = getflag(tok[2])
-            p3 = "NOPRM"
-
-        elif len(tok) == 4:
-            name = "{}_{}_{}_{}".format(tok[0], tok[1], tok[2], tok[3])
-            p1 = getflag(tok[1])
-            p2 = getflag(tok[2])
-            p3 = getflag(tok[3])
+            n = 0
 
         else:
-            name = "__TOK_ERROR__"
-            p1 = "__TOK_ERROR__"
-            p2 = "__TOK_ERROR__"
-            p3 = "__TOK_ERROR__"
+            assert(len(tok) == 2)
+            n = tok[1]
 
-        ls.write("{}{}\n".format(deprecated, name))
+        ls.write("{}{}\n".format(deprecated, tok[0]))
 
         hd.write("#ifdef _NEED_ARCH_I\n")
-        hd.write('{{ "{}{}", "{}{}", {}, {}, {}, i_{} }},\n'\
-                    .format(deprecated, tok[0], deprecated, name, p1, p2, p3, tok[0]))
+        hd.write('{{ "{}{}", {}, i_{} }},\n'\
+                    .format(deprecated, tok[0], n, tok[0]))
         hd.write("#else\n")
-        hd.write("#define I_{} {}\n".format(name.upper(), count))
+        hd.write("#define I_{} {}\n".format(tok[0].upper(), count))
         hd.write("extern bool i_{}(ctx_t *, acc_t *, acc_t *, acc_t *, ulong *, ulong *, ulong *);\n"
                     .format(tok[0]))
         hd.write("#endif\n\n")
diff --git a/vm/in/instrs.h b/vm/in/instrs.h
index e21beb5..49e24e0 100644
--- a/vm/in/instrs.h
+++ b/vm/in/instrs.h
@@ -9,6 +9,15 @@
 uint i_##name(ctx_t *ctx, acc_t *p1, acc_t *p2, acc_t *p3,                  \
                           ulong *r1, ulong *r2, ulong *r3)                  \
 
+#define XSRCP(v, p, x)                                                      \
+    if (ACC_FMT_IS_MEM(p->type))                                            \
+        v = readmem##x(ctx, p->addr, p->mlen);                              \
+    else v = p->val;                                                        \
+
+#define SRCP(p)                                                             \
+    if (__builtin_expect(ACC_FMT_IS_MEM(p->type), 0))                       \
+        p->val = readmemsx(ctx, p->addr, p->mlen);                          \
+
 //----------------------------------------------------------------------------//
 
 #define INTO() \
diff --git a/vm/in/mem.c b/vm/in/mem.c
index 13c1f92..c615d3a 100644
--- a/vm/in/mem.c
+++ b/vm/in/mem.c
@@ -17,14 +17,10 @@ IMPL_START(loop) {
 
 IMPL_START(b)
 {
-    ulong v;
+    SRCP(p1);
+    SRCP(p2);
 
-    if (ACC_FMT_IS_MEM(p1->type))
-        v = readmemsx(ctx, p1->addr, p1->mlen);
-    
-    else v = p1->val;
-
-    COMPARE_SUB(v, p2->val);
+    COMPARE_SUB(p1->val, p2->val);
 
     if (eval_cond(ctx, ctx->cond))
         R(RIP) = p3->val;
@@ -34,14 +30,9 @@ IMPL_START(b)
 
 IMPL_START(cmp)
 {
-    ulong v;
+    SRCP(p1);
 
-    if (ACC_FMT_IS_MEM(p1->type))
-        v = readmemsx(ctx, p1->addr, p1->mlen);
-    
-    else v = p1->val;
-
-    COMPARE_SUB(v, p2->val);
+    COMPARE_SUB(p1->val, p2->val);
 
     return 0;
 }
@@ -49,44 +40,20 @@ IMPL_START(cmp)
 //----------------------------------------------------------------------------//
 
 IMPL_START(lea) { *r1 = p2->addr; return 1; }
+IMPL_START(mov) { XSRCP(*r1, p2, sx); return 1; }
+IMPL_START(movzx) { XSRCP(*r1, p2, zx); return 1; }
 
-IMPL_START(mov)
-{
-    if (ACC_FMT_IS_MEM(p2->type))
-        *r1 = readmemsx(ctx, p2->addr, p2->mlen);
-
-    else *r1 = p2->val;
-
-    return 1;
-}
-
-IMPL_START(movzx)
-{
-    if (ACC_FMT_IS_MEM(p2->type))
-    {
-        if (__builtin_expect(p2->mlen == 8, 0))
-            _except(ctx, E_ILL, "MOVZX with qword memory source");
-
-        *r1 = readmemzx(ctx, p2->addr, p2->mlen);
-    }
-
-    else *r1 = p2->val;
-
-    return 1;
-}
-
-IMPL_START(movsxb) { *r1 = (ulong)(long)(char)(p2->val & 0xFF); return 1; }
-IMPL_START(movsxw) { *r1 = (ulong)(long)(short)(p2->val & 0xFFFF); return 1; }
-IMPL_START(movsxd) { *r1 = (ulong)(long)(int)(p2->val & 0xFFFFFFFF); return 1; }
+IMPL_START(movsxb) { SRCP(p2); *r1 = (ulong)(long)(char)p2->val; return 1; }
+IMPL_START(movsxw) { SRCP(p2); *r1 = (ulong)(long)(short)p2->val; return 1; }
+IMPL_START(movsxd) { SRCP(p2); *r1 = (ulong)(long)(int)p2->val; return 1; }
 
 IMPL_START(xchg)
 {
+    SRCP(p1);
+    SRCP(p2);
+
     *r2 = p1->val;
-
-    if (ACC_FMT_IS_MEM(p2->type))
-        *r1 = readmemsx(ctx, p2->addr, p2->mlen);
-
-    else *r1 = p2->val;
+    *r1 = p2->val;
 
     return 2;
 }
@@ -99,15 +66,10 @@ IMPL_START(xchg)
 
 IMPL_START(push)
 {
-    ulong v;
-
-    if (ACC_FMT_IS_MEM(p1->type))
-        v = readmemzx(ctx, p1->addr, p1->mlen);
-
-    else v = p1->val;
+    XSRCP(p1->val, p1, zx);
 
     R(RSP) -= 8;
-    writemem(ctx, v, R(RSP), 8);
+    writemem(ctx, p1->val, R(RSP), 8);
 
     return 0;
 }
@@ -122,17 +84,41 @@ IMPL_START(pop)
 
 IMPL_START(call)
 {
+    SRCP(p1);
+
     R(RSP) -= 8;
     writemem(ctx, R(RIP), R(RSP), 8);
     R(RIP) = p1->val;
 
-    if (p2)
-    {
-        R(AX0) = p2->val;
+    return 0;
+}
 
-        if (p3)
-            R(AX1) = p3->val;
-    }
+IMPL_START(xcall2)
+{
+    SRCP(p1);
+    SRCP(p2);
+
+    R(RSP) -= 8;
+    writemem(ctx, R(RIP), R(RSP), 8);
+
+    R(RIP) = p1->val;
+    R(AX0) = p2->val;
+
+    return 0;
+}
+
+IMPL_START(xcall3)
+{
+    SRCP(p1);
+    SRCP(p2);
+    SRCP(p3);
+
+    R(RSP) -= 8;
+    writemem(ctx, R(RIP), R(RSP), 8);
+
+    R(RIP) = p1->val;
+    R(AX0) = p2->val;
+    R(AX1) = p3->val;
 
     return 0;
 }
diff --git a/vm/in/misc.c b/vm/in/misc.c
index 5925472..a35cce7 100644
--- a/vm/in/misc.c
+++ b/vm/in/misc.c
@@ -81,6 +81,8 @@ IMPL_START(cls)
 
 IMPL_START(bswap)
 {
+    SRCP(p2);
+
     ulong v = p2->val;
 
     *r1 = ((v & 0xFF00000000000000) >> 56)
@@ -97,6 +99,8 @@ IMPL_START(bswap)
 
 IMPL_START(wswap)
 {
+    SRCP(p2);
+
     ulong v = p2->val;
 
     *r1 = ((v & 0xFFFF000000000000) >> 48)
@@ -109,6 +113,8 @@ IMPL_START(wswap)
 
 IMPL_START(dswap)
 {
+    SRCP(p2);
+
     *r1 = ((p2->val & 0xFFFFFFFF00000000) >> 32)
         | ((p2->val & 0x00000000FFFFFFFF) << 32);
 
@@ -121,6 +127,8 @@ IMPL_START(dswap)
 
 IMPL_START(prn)
 {
+    SRCP(p1);
+
     ulong v = p1->val;
 
     // Magic value? :)
@@ -135,6 +143,9 @@ IMPL_START(prn)
 
 IMPL_START(prns)
 {
+    if (p1->type != A_REG)
+        _except(ctx, E_ILL, "PRNS given a non-REG operand");
+
     uchar ch = readmemzx(ctx, R(p1->reg), 1);
 
     COMPARE_SUB(ch, 0);
diff --git a/vm/in/string.c b/vm/in/string.c
index ca10056..614352d 100644
--- a/vm/in/string.c
+++ b/vm/in/string.c
@@ -13,6 +13,9 @@
 
 static void stos_impl(ctx_t *ctx, acc_t *p1, acc_t *p2, uint len)
 {
+    if (p1->type != A_REG)
+        _except(ctx, E_ILL, "STOSX given a non-REG operand");
+
     writemem(ctx, p2->val, R(p1->reg), len);
     STR_MOVE(p1->reg, len);
 }
@@ -26,6 +29,9 @@ IMPL_START(stosq) { stos_impl(ctx, p1, p2, 8); return 0; }
 
 static void scas_impl(ctx_t *ctx, acc_t *p1, acc_t *p2, uint len)
 {
+    if (p1->type != A_REG)
+        _except(ctx, E_ILL, "SCASX given a non-REG operand");
+
     ulong x = readmemsx(ctx, R(p1->reg), len);
     COMPARE_SUB(x, p2->val);
 
diff --git a/vm/pc/console.c b/vm/pc/console.c
index 7b99c8b..0e35985 100644
--- a/vm/pc/console.c
+++ b/vm/pc/console.c
@@ -3,18 +3,23 @@
 
 #include <pc/console.h>
 
+// FIXME XXX
+
+//#define _LARGE_SCREEN
+
 #ifndef _LARGE_SCREEN
-#   define CONSOLE_WIDTH 80
-#   define CONSOLE_HEIGHT 25
-#   define CONSOLE_FONT_SIZE 16
+#   define _MULT 1
 #else
-#   define CONSOLE_WIDTH 160
-#   define CONSOLE_HEIGHT 50
-#   define CONSOLE_FONT_SIZE 32
+#   define _MULT 2
 #endif
 
-#define SCREEN_WIDTH (9 * CONSOLE_WIDTH)
-#define SCREEN_HEIGHT (16 * CONSOLE_HEIGHT)
+#define CONSOLE_WIDTH       (80)
+#define CONSOLE_HEIGHT      (25)
+#define CONSOLE_FONT_SIZE   (16 * _MULT)
+#define SCREEN_WIDTH        (9 * CONSOLE_WIDTH * _MULT)
+#define SCREEN_HEIGHT       (16 * CONSOLE_HEIGHT * _MULT)
+
+#define _SURF_H             CONSOLE_FONT_SIZE
 
 SDL_Window *scr_win = NULL;
 SDL_Renderer *scr_rend = NULL;
@@ -281,7 +286,7 @@ void console_putc(ctx_t *ctx, char ch)
         for (y = 0; y < CONSOLE_HEIGHT-1; y++)
             if (scr_rects[y] != NULL)
             {
-                scr_rects[y]->y -= 16; // surf->h
+                scr_rects[y]->y -= _SURF_H; // surf->h
             }
 
         console_render(ctx);
diff --git a/vm/pc/decode.c b/vm/pc/decode.c
index da4aa30..9a368a5 100644
--- a/vm/pc/decode.c
+++ b/vm/pc/decode.c
@@ -62,34 +62,31 @@ static void checkreg(ctx_t *ctx, uint reg)
 //
 // Verify that given access length is that of a byte/word/dword/qword
 //
-static void checklength(ctx_t *ctx, uint len)
+static void checklength(ctx_t *ctx, instr_t *in, uint len)
 {
     static const int lentab[9] = { 0, 1, 1, 0, 1, 0, 0, 0, 1 };
 
     if (len > 8 || lentab[len] == 0)
-        _except(ctx, E_ILL, "Invalid memory access length: %u", len);
+        _except(ctx, E_ILL, "%s: Invalid memory access length: %u",
+                    in->name, len);
 }
 
 //
 // Extracts one operand
 //
-static void extract_param(ctx_t *ctx,  uint prm, acc_t *p)
+static void extract_param(ctx_t *ctx, instr_t *in, acc_t *p)
 {
     // Get next operand ModRM-like byte
     uchar fmt = fetchb(ctx);
 
-    ulong hi = (fmt & 0b11100000) >> 5;
-    ulong lo = fmt & 0b00011111; 
+    uchar hi = (fmt & 0b11100000) >> 5;
+    uchar lo = fmt & 0b00011111; 
 
     //
     // Registers
     //
     if (hi == 0)
     {
-        if (prm != P_REG)
-            _except(ctx, E_ILL, "Not expecting a register: %s",
-                    ctx->cur_in->full);
-
         p->reg = lo;
         p->type = A_REG;
         checkreg(ctx, p->reg);
@@ -104,10 +101,6 @@ static void extract_param(ctx_t *ctx,  uint prm, acc_t *p)
     //
     if (hi == 7)
     {
-        if (prm != P_IMM)
-            _except(ctx, E_ILL, "Not expecting an immediate: %s",
-                    ctx->cur_in->full);
-
         switch (lo)
         {
         case 1:
@@ -131,7 +124,8 @@ static void extract_param(ctx_t *ctx,  uint prm, acc_t *p)
             break;
 
         default:
-            _except(ctx, E_ILL, "Invalid immediate length: %hhu", lo);
+            _except(ctx, E_ILL, "%s: Invalid immediate length: %hhu",
+                    in->name, lo);
         }
 
         return;
@@ -141,11 +135,7 @@ static void extract_param(ctx_t *ctx,  uint prm, acc_t *p)
     // Memory operands
     //
 
-    if (prm != P_MEM)
-        _except(ctx, E_ILL, "Not expecting a memory access: %s",
-                ctx->cur_in->full);
-
-    checklength(ctx, lo);
+    checklength(ctx, in, lo);
     p->mlen = lo;
 
     switch (hi)
@@ -234,31 +224,31 @@ void decode(ctx_t *ctx)
     ctx->cond = b2 & SUFF_COND;
 
     // Operand 1?
-    if (in->prm1 == NOPRM)
+    if (in->nprms == 0)
     {
         exec_instr(ctx, in, NULL, NULL, NULL, lock, rep);
         return;
     }
 
-    extract_param(ctx, in->prm1, &p1);
+    extract_param(ctx, in, &p1);
 
     // Operand 2?
-    if (in->prm2 == NOPRM)
+    if (in->nprms == 1)
     {
         exec_instr(ctx, in, &p1, NULL, NULL, lock, rep);
         return;
     }
 
-    extract_param(ctx, in->prm2, &p2);
+    extract_param(ctx, in, &p2);
 
     // Operand 1?
-    if (in->prm3 == NOPRM)
+    if (in->nprms == 2)
     {
         exec_instr(ctx, in, &p1, &p2, NULL, lock, rep);
         return;
     }
 
-    extract_param(ctx, in->prm3, &p3);
+    extract_param(ctx, in, &p3);
 
     exec_instr(ctx, in, &p1, &p2, &p3, lock, rep);
 }
diff --git a/vm/pc/decode.h b/vm/pc/decode.h
index 225c40e..4a1c266 100644
--- a/vm/pc/decode.h
+++ b/vm/pc/decode.h
@@ -66,12 +66,7 @@ enum { NOPRM, P_REG, P_IMM, P_MEM=4 };
 struct instr_t
 {
     char   *name;
-    char   *full;
-
-    uint    prm1;
-    uint    prm2;
-    uint    prm3;
-
+    uint    nprms;
     uint  (*func)(ctx_t *, acc_t *, acc_t *, acc_t *,
                            ulong *, ulong *, ulong *);
 };
diff --git a/vm/pc/exec.c b/vm/pc/exec.c
index fa3d468..ce79ebd 100644
--- a/vm/pc/exec.c
+++ b/vm/pc/exec.c
@@ -41,12 +41,10 @@ bool eval_cond(ctx_t *ctx, uint cond)
 #define OUTPUT(p, r) {                                                      \
     if (p->type == A_REG)                                                   \
         R(p->reg) = r;                                                      \
-    else if (p1->type == A_IMM64)                                           \
-        _except(ctx, E_ACC, "Trying to output to an IMM64");                \
-    else {                                                                  \
-        assert(ACC_IS_MEM(p));                                              \
+    else if (ACC_IS_MEM(p))                                                 \
         writemem(ctx, r, p->addr, p->mlen);                                 \
-    } }
+    else _except(ctx, E_ACC, "Trying to output to an IMM");                 \
+    }
 
 //
 // Executes an instruction
diff --git a/vm/pc/main.c b/vm/pc/main.c
index c67d3a5..9cda77e 100644
--- a/vm/pc/main.c
+++ b/vm/pc/main.c
@@ -62,7 +62,7 @@ int main(int argc, char **argv)
     main_ctx.r = arch_r;
     main_ctx.i = arch_i;
 
-#if 1 && !defined(NDEBUG)
+#if 0 && !defined(NDEBUG)
     main_ctx.dumpsw = 1;
 #endif