ABelliqueux
/
psx-spx.github.io
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Merge pull request #4 from ramapcsx2/patch-1 

Added confirmation about the wasted 32k CD buffer
This commit is contained in:
Nicolas Noble 2020-10-19 23:36:16 -07:00 committed by GitHub
parent 64169f9d29 59afd016d6
commit f572176f4a
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 22 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
cdromdrive.md
View File

@ -1820,6 +1820,28 @@ before the cdrom controller receives and skips further sectors). Otherwise
sectors would be lost without notice (there appear to be absolutely no overrun
status flags, nor overrun error interrupts).<br/>
#### Update:
This is confirmed, as found in the SCEA_BBS.pdf bulletin board archive:
```
12/29/95 10:24 AM
Re(4): CD buffer
Thomas Boyd
CD
Dan Burnash
OK. This is the story of the CD ROM subsystem sector buffer:
The CD-ROM subsystem sector buffer is currently 32K. It is located in the CD-ROM subsystem.
It uses a sort-of tripple buffering system to read sectors in and make one (and ONLY one) sector
available to the user.
Common questions that spring to mind and their answers:
Q: 32K - (2352 bytes/sector)*(3 buffered sectors) = lots of leftover RAM! Can I use it? A: No. It is
not accessible by anything but the CD-ROM subsystem.
Q: How dissappointing. As consolation, can I be told what the extra memory is used for? A: The
memory was going to be used for sound mapping, but (1) the system would be too slow, and
(2) sound mapping is already done by the SPU. The current implementation of this memory is ...
nothing. It is vestigal and will be cut out in future manufacturing cost reduction designs.
Tom
```
#### Sector Buffer Test Cases
```
Setloc(0:2:0)+Read