[GerbilSoft]

I'd like to document how the MD's version register corresponds to the hardware version. Specifically, I want to find out if the "version" field (low 4 bits) can be anything other than 0 (no TMSS) or 1 (has TMSS).

In order to do this, we need some way to display the contents of the version register, preferrably without having to build a flash cart. So, here it is: a set of patch codes!

These codes require a copy of Sonic 1 (REV00) and either a Game Genie or Pro Action Replay.

Game Genie codes:

HHEA-DENE
YHEA-CAEG
ADEA-CAEJ
AMEA-CA6L

Pro Action Replay codes:

01C884:3239
01C886:00A1
01C888:0000
01C88A:6002

Once the code's enabled, start Sonic 1, then enable Debug Mode in a level. The first four digits of the Debug Mode screen coordinates will be replaced with the contents of the version register.

Please test this out and post the first four digits of the Debug Mode display here, along with information about what system you tested it on:

• System model (e.g. Genesis 1, Genesis 2, Nomad)
  
• If Genesis 1: does it have the EXT port and/or "High Definition Graphics"?
  
• System region.
  
• Board revision, if known.
  
• Does the system have TMSS? (I.e. the "PRODUCED BY" screen on startup)
  
• Any accessories connected to the system.

I'll start off the list:

• Sega Nomad (U): 0xA1A1
  
• Gens/GS II (RomCartridgeMD-v0/ba5e1551) (U): 0x00A0
  
• Gens/GS r7 (U): 0x00A0
  
• Kega Fusion 3.63x without TMSS (U): 0xA0A0
  
• Kega Fusion 3.63x with TMSS (U): 0xA0A0
  
• Regen/GTK+ 0.95 (U): 0xA0A0

(Looks like bytewide reads to the $A1xxxx area should return the byte duplicated in both halves of the word, something Gens, Gens/GS, and Gens/GS II don't do right now.)

EDIT: Replaced the last two codes with a short branch. Overlord's Game Genie complained about two "similar" codes, which is odd since I've never had a single error message on mine. Maybe it's a different ROM revision?
EDIT 2: Turns out it was actually a typo, but four codes is shorter than five, so I'll keep it like that.

This post has been edited by GerbilSoft: 26 May 2013 - 03:16 PM
Reason for edit: Two 4E71s failed on Overlord's Game Genie.

[MainMemory]

US Genesis 1, with EXT port, "High Definition Graphics", TMSS, no accessories: A1A1.
US Genesis 2: lol my Sonic 1 cart is too broken to run on it

[Billy]

0x8181
Genesis 2
USA
Unknown board Revision
Yes TMSS
32X and Sega CD connected

Pretty sure I did everything correctly...

This post has been edited by Billy: 25 May 2013 - 10:39 PM

[TmEE]

There's nothing but 0 and 1 used by the hardware Sega released. The version bits come out the IO chip and there's not a lot of variety between these. I suppose some games will break when there's some other values...

[GerbilSoft]

TmEE, on 25 May 2013 - 11:19 PM, said:

There's nothing but 0 and 1 used by the hardware Sega released. The version bits come out the IO chip and there's not a lot of variety between these. I suppose some games will break when there's some other values...

That's what I figured. I just wanted to verify if there was some random variant that had something else there.

Billy, on 25 May 2013 - 10:39 PM, said:

0x8181
Genesis 2
USA
Unknown board Revision
Yes TMSS
32X and Sega CD connected

Pretty sure I did everything correctly...

0x8181 is the right value for a US Genesis with TMSS and a Sega CD connected. (Sega CD pulls down the /DISK line on the expansion port, which is wired to bit 5 of the version register.)

This post has been edited by GerbilSoft: 25 May 2013 - 11:22 PM

[Overlord]

EU Multimega spits out C1C1. All I had connected was a P1 pad.