Jul -- The Cutting Room Floor: Virtua Racing (MD/32x) findings

Tamkis
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Posted on 10-09-13 05:53:49 AM (last edited by Tamkis at 10-09-13 03:50:00 PM)

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A few days ago, I decided to open up the rom file for the Sega Genesis and Sega 32x version of Virtua Racing in a hex editor, to see if there was any TCRF-worthy material inside. You know, the only MD game with the fancy Sega Virtua Processor (SVP) chip in it, and with the awesome 3D graphics. I did not perform a Motorola 68k nor Hitach SH-2 disasm for either version, as dissasembling are above my head; however, I did perform a simple peek for string-based data.

Some interesting things were found, especially for the special SVP MD version. Below are some text strings, and their ROM addresses, for both the Genesis/32x versions. Some are unused, while others are simply in-game text (useed), which I decided to list anyways, for potential ROM-hackers.
--

Virtua Racing MD:

$4E07
(Garbage? Or character sets? There seems to be a lot of unusual type of padding like this throughout the rom. On the hexadecimal level, each character's value is incremented by 1, which is... odd.)
!"#$%&`()0123456789@ABCDEFGHIPQRSTUVWXY

$4F6C (Debug info!)
Communication Error!
DRAM clear check
Draw start
Read error !!
Line length over !!
Calculate matrix
Make polygon data
Draw polygon
Draw bitmap
DSP completed
ST reg error !!
Soft SP error !!

$1B376 (Debug info!)
ROM CHECKSUM 1
DRAM R/W 2
DSP ROM RD 3
DSP DRAM R/W 4
DSP IRAM R/W 5
DSP DRAM OVER WRITE 6
DSP POINTER

$1b3fc (Debug info!)
ERROR SKIP OK??
COMMUNICATION ERROR !!!!!

$20028 ("SEGA" TMSS String?)
SEGA

$2ECFD (In-game text)

INSTANT REPLAY? YES NO

$2FBF9 (In-game text)
\<=> RANKING \<=>
@
RANK
NAME
TIME
VR MODE

\<=> FASTEST LAP \<=>
1st
2nd
3rd
4th
5th
6th
7th
8th
9th

10th
11th
12th
13th
14th
15th

16th
17th
18th
19th
20th
21st

22nd
23rd
24th

$2FF9C (In-game text)
BEGINNER
COURSE RANKING
MEDIUM
COURSE RANKING
EXPERT
COURSE RANKING
EXIT
RECORDS

$301CE (In-game text)
BIG FOREST
BAY BRIDGE
ACROPOLIS

$33075 (In-game text)
PLAYER 1
PLAYER 2
PRESS A,B,OR C
----

Virtua Racing DX (32x)

$202A3 (What appears to be uncompiled Hitachi SH-2 Code? Repeats twice)
RSRV;
INST3
SLOT
CPUA
DMA
NMI
UBRK
TRAP
IRL
=====

What is most interesting in my findings are what ~~I strongly believe to be the~~ is debug info for the SVP MD version of Virtua Racing. For those who do not know, this version of virtua racing was recently emulated, via Notaz PicoDrive emulator ports. According to the Notaz's notes and other's research, the SVP is actually a Samsung SSP1601 DSP processor, which drives polygon drawing. ~~The contents of some of the strings, which mention "DSP", "polygon", matrix", do seem to be related to some kind of debug function.~~

~~Also, according to Notaz's notes, he mentions that somewhere in the rom is indeed an arcade style SMC function. These strings must have something to do with it!~~

~~Originally posted by "Notaz's docs"~~

-------------------------------------------------------------------------------
4. Other notes
-------------------------------------------------------------------------------

The game has arcade-style memory self-check mode, which can be accessed by
pressing _all_ buttons (including directions) on 3-button controller. There was
probably some loopback plug for this...

The entry point for the code seems to be at address 0x800 (word 0x400) in ROM,
but it is not clear where the address is fetched from when the system powers
up. The memory test code also sets up "ld PC, .." opcodes at 0x7f4, 0x7f8 and
0x7fc, which jump to some routines, possibly interrupt handlers. This means
that mentioned addresses might be built-in interrupt vectors.

I tried (and nearly failed, physically) at pressing "_all_" butons at once on his emulator with VR running at the title screen, but nothing happened. Also, I noted that those debug strings are not in the 32x version, which shows further support that they are SVP-specific debug info. (The 32x version did 3D via its sheer horsepower.)

As for the 32x version, that data at that single rom address appears to be some kind of uncompiled SH-2 commands; however, I am not entirely sure. I also found an Easter Egg in the 32x version, in the form of a Sonic reference. If you go backwards on Sand Park, before the fork in the road, you will find the word "Knuckles"!

----

~~So, does anyone more knowledgable on Sega Genesis ROM hacking (Andlabs?) want to research for and enable the long lost SMC debug data? Is there a known SMC for the Arcade version of Virtua Racing?]~~

I do not have a TCRF account, so if anybody wants to throw this data on the wiki, be my guest

EDIT: Verified to indeed be debug data, and to also be accessable on hardware! So next post...

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