From 59afd016d66e85bc28c2313c06672fb9b6caab8a Mon Sep 17 00:00:00 2001 From: Robert Neumann Date: Tue, 20 Oct 2020 08:35:01 +0200 Subject: [PATCH] Added confirmation about the wasted 32k CD buffer --- cdromdrive.md | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/cdromdrive.md b/cdromdrive.md index a51833c..bdf409a 100644 --- a/cdromdrive.md +++ b/cdromdrive.md @@ -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).
+#### 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