Sega Model 2/3 step revision vs conversions

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    • Sega Model 2/3 step revision vs conversions

      Can someone enlighten me as to what's the deal with Model 2/3 step revisions and conversions?

      From what i've read you can only convert a model 2/3 board to another game of the same step (of the donor board) but what is the reason for this limitation? is it something in the roms which dictates this?

      Take model 3 for example, each step just ups the CPU clock speed with the exception of 2.1 which just changes the package type of some custom IC's (according to system16). What stops a higher step board running games from a lower step?

      I can see the logic in a higher step game not running on older, slower hardware but the other way around?
    • Old thread but I just saw this and thought Id' chime in.

      There are other differences beyond clock speed, the ROM mapping is different and there are other bits of hardware too.

      So Model 2 has 4 versions
      Model 2o (original)
      Model 2A CRX
      Model 2B CRX
      Model 2C CRX

      From what I can see from the MAME driver B and C both have texture ram and a co-processor while original and A do not.

      original and A are pretty similar but o has less normal RAM with some extra dual-port ram while A has more normal ram but no dual-port RAM (Maybe some else who knows this hardware better can chime in with any corrections/other differences)

      It might be possible to get 2o games to work on 2A hardware, and to get 2B and 2C games to work on the other hardware but I don't think you'll ever get 2B or 2C games working on 2A hardware.

      Changing which version the game runs on would likely require some patching to deal with the differences.


      Model 3 has 4 versions as well:

      Model 3 Step 1.0
      Model 3 Step 1.5
      Model 3 Step 2.0
      Model 2 Step 2.1

      Step 2.0 and Step 2.1 are functionally identical and games on one can work on the other.

      Looking at MAME source here the clock speed is different from 1.0 to 1.5 to 2.0 and some of the hardware looks mapped differently as well. The ROM boards are laid out different too. Again, it might be possible to port games between steps but would require some patching to do so.
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    • Digital Systems Design wrote:

      Step 1 had some errors on the planet chip designs - hence it was barely used and quickly replaced with the Step 1.5 system
      can Step 1.5 system play step 1.0 games?
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    • I've been told 2A games run fine on a 2B, though I haven't tested this with my Dynamite Cop 2A romboard yet. This is incorrect

      It's also been stated by Yu Suzuki that the Fighting Vipers 2B board was clocked higher than the other 2B boards to handle the higher polygon count of the game. I suspect this might have been a stretched truth generated by the development team like "Blast Processing" as I can't find any physical revision differences on my newly obtained Fighting Vipers board to my Virtua Striker 2 board.
      My Model2 hardware interest goes back over a decade! 08/05 - Unused character found in Sonic the Fighters | 01/06 - Memory Exploration | 01/07 - All findings published on Sonic CulT

      The post was edited 1 time, last by biggestsonicfan ().

    • biggestsonicfan wrote:

      I've been told 2A games run fine on a 2B
      I don't think that's true, though I would be very happy to be wrong.

      Games released on both 2A and 2B seem to always have different program ROMs depending on the hardware.
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    • New

      biggestsonicfan wrote:

      I've been told 2A games run fine on a 2B, though I haven't tested this with my Dynamite Cop 2A romboard yet.

      It's also been stated by Yu Suzuki that the Fighting Vipers 2B board was clocked higher than the other 2B boards to handle the higher polygon count of the game. I suspect this might have been a stretched truth generated by the development team like "Blast Processing" as I can't find any physical revision differences on my newly obtained Fighting Vipers board to my Virtua Striker 2 board.
      Maybe the clock settings can be configured in software during boot?
    • New

      twistedsymphony wrote:

      biggestsonicfan wrote:

      I've been told 2A games run fine on a 2B
      I don't think that's true, though I would be very happy to be wrong.
      Games released on both 2A and 2B seem to always have different program ROMs depending on the hardware.
      Ah, you are right, my bad. I misremembered an email I had sent Ken at irepairsega. He said it wasn't going to work, not that it was. My mistake.

      Fluffy wrote:

      biggestsonicfan wrote:

      I've been told 2A games run fine on a 2B, though I haven't tested this with my Dynamite Cop 2A romboard yet.

      It's also been stated by Yu Suzuki that the Fighting Vipers 2B board was clocked higher than the other 2B boards to handle the higher polygon count of the game. I suspect this might have been a stretched truth generated by the development team like "Blast Processing" as I can't find any physical revision differences on my newly obtained Fighting Vipers board to my Virtua Striker 2 board.
      Maybe the clock settings can be configured in software during boot?
      Entirely possible but I've yet to find out how that works.
      My Model2 hardware interest goes back over a decade! 08/05 - Unused character found in Sonic the Fighters | 01/06 - Memory Exploration | 01/07 - All findings published on Sonic CulT
    • New

      Digital Systems Design wrote:

      twistedsymphony wrote:

      can Step 1.5 system play step 1.0 games?
      No sadly not - well I say that, I have never actually tried to do that but I am pretty sure the mapping is different due to the changes that were made - give it a go but pretty sure it will not work
      I can confirm it isn't possible. The Mame driver stated booting Scud Race on a Step 1.0 video board will give a "JUPITER ASIC HAS THE WRONG ID CODE" error.

      As for the CPU boards between step 1.0 and 1.5, they are identical. I couldn't find anything on either board that would change the clock of the main cpu from 66 MHz to 100 MHz. Either Step 1.5 games run at 66 MHz or something else is going on.

      As for Model 2, the hardware across all versions is different:

      Model 2o (original): 5x TGP/MB86234, Model 1 sound board
      Model 2A CRX: 5x TGP/MB86234, SCSP sound board
      Model 2B CRX: 2x SHARC/ADSP-21062, SCSP sound board
      Model 2C CRX: 2x TGPx4/MB86235, SCSP sound board

      So Model 2 and 2A are nearly identical but with slightly different address mappings. The fact that Fighting Vipers has its cpu clock speed increased may be incorrect as the SHARC co-processor seems to be more powerful than the TGP. 2C's TGPx4 looks to have even more graphical capabilities (House of the Dead 1 for example).

      The post was edited 1 time, last by Hydreigon ().