Strange Frankestein Hardware - Turn SMS into a computer

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By Sander

Founder (1871)

Sander's picture

20-05-2009, 23:27

VDP
To quote Charles MacDonald from his "Sega Master System VDP documentation":

"The Video Display Processor (VDP) is a graphics chip derived from the
Texas Instruments TMS9918, used by Sega in their video game consoles and
arcade hardware. There are four versions of the VDP:

315-5124 - Used in the Mark III, Sega Master System.
315-5246 - Used in the SMS 2 and later versions of the SMS.
315-5378 - Used in the Game Gear.
315-5313 - Used in the Genesis and Mega Drive."

Sound
The Texas Instruments SN76489 Programmable Sound Generator (PSG) is built into the VDP, and is identical to the standalone version. It is also used in the MSX and the BBC Micro.
Standard PSG: Three tone and one noise channel. In most Japanese, and maybe some European machines, a FM-unit is present (Yamaha YM2413).

By muffie

Paladin (933)

muffie's picture

20-05-2009, 23:43

sound chip is NOT the same.. They're similar, but not equal.
Mark III VDP, AFAIK, is very similar with MSX one, but SMS has a new mode that's used by most of it's games...

By Sander

Founder (1871)

Sander's picture

20-05-2009, 23:56

The 315-5124 Chip is the only one that has some backwards compatibility with the TMS9918A.

Apart from the Sega Master System, it's predecessor the Sega Mark III also used the 315-5124 Videochip. There's a Japanese page describing the chips and pin layout here:

http://www2.odn.ne.jp/~haf09260/Mark3/EnrM3.htm (you have to manually set the text decoding of your browser to Shift-Jis, else the page just looks messy with random ascii characters.

Excite translation here (with messed up layout):

http://www.excite-webtl.jp/world/english/web/?wb_url=http://www2.odn.ne.jp/~haf09260/Mark3/EnrM3.htm&wb_lp=JAEN&wb_dis=2

By Sander

Founder (1871)

Sander's picture

20-05-2009, 23:59

Well, if you want to Frankenstein your MSX1, the 315-5124 would be the only option I guess. It has mode 1,2,3 and the new mode 4.

By muffie

Paladin (933)

muffie's picture

21-05-2009, 12:52

ok, but that's the question... Is it possible to frankstein the MSX by just replacing the VDP?

By nikodr

Paladin (748)

nikodr's picture

21-05-2009, 15:03

Well it would be better to use the msx as a power supply unit and place a small scale sms in a cartridge.It works 100% and only uses the msx as power supply.

By dhau

Paragon (1570)

dhau's picture

21-05-2009, 15:56

Well it would be better to use the msx as a power supply unit and place a small scale sms in a cartridge.It works 100% and only uses the msx as power supply.

Better yet, to save on edge connector, make it fully stand-alone mini-SMS with it's own power supply, so you can use MSX at the same time. Oh wait, SEGA beat everyone to it Tongue

By muffie

Paladin (933)

muffie's picture

21-05-2009, 16:12

Well, if you want to think it that way, it could be better to place a mini-itx board with an ssd drive inside a Panasonic MSX case, loaded with an MSX emulator...

By dhau

Paragon (1570)

dhau's picture

21-05-2009, 16:58

Well, if you want to think it that way, it could be better to place a mini-itx board with an ssd drive inside a Panasonic MSX case, loaded with an MSX emulator...

No it's not better at all. I would rather call my bike Lucy and write love poems for it about being young and fast, and have an awesome frame!

By e_sedes

Expert (112)

e_sedes's picture

21-05-2009, 19:54

The 315-5124 Chip is the only one that has some backwards compatibility with the TMS9918A.
The 315-5124, 315-5246 and 315-5378 chips (SMS, SMS2 and Game Gear VDPs) are TMS9918A software compatibles.
Look at this: SMS VDP

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