Saturn technical question on KoF'95's cartridge

[CHAZumaru °_°]

Saturn technical question on KoF'95's cartridge

Hi to ya all, I'm new to the board.

I have a pretty technical question to ask to confirmed Saturn developpers or (don't ban, wait and read ^^) emulator creators. In a nutshell, to anyone with a deep hardware basis.

The Sega Saturn has 2 (official) RAM cartirdges to increase it's RAM for games such as SNK or Capcom arcade convertions...

But there are also 2 games, "The King Of Fighters'95" and "Ultraman Hikari No Kyojin Densetsu" that use a specific ROM cartridge. Let's forget about the second game and focus on KoF'95.

What I would like to know -the most accurately possible- is :

WHAT is in the ROM cartridge of the game ?

What is stocked in it ?

And why did they pick a ROM cartridge instead of a simple RAM extension (like they did afterwoods for obvious financial reasons) ?

A programmer I know (who has no experience of the Saturn) made the hypothesis that there’s a DSP inside the ROM, like the Sega Virtua Processor in Virtua Racing for Megadrive/Genesis system.

But the Yamaha SCSP DSP which serves as an link between the 68EC000 sound processor and the Audio-RAM would have been able to play that role, wouldn’t it ?

I also found out on gameFAQs a guide from John Hokanson Jr mentioning this :

“King of Fighters '95 used a special 1 Megabyte ROM cartridge that

predated the use of RAM cartridges. The ROM cartridge came packaged

with KOF '95, and was manufactured by SNK and Sega. It included all

the additional textures needed by the game in self-contained ®ead

(O)nly (M)emory chips.”

I know that textures and backgrounds are dealed by the VDP2 chip. Is the cartridge related somehow to the VDP2, giving him special access to the ROM information ? Therefore the disc information would be sent to the VDP1 and the the cart’s info to the VDP2 ? But then how come the ROM cart is only 1MB ?

I’m asking this after having searched for an answer for a whole week as this question emerged after a long forum discussion .

We can’t find any answer, please help us, we’re dying (almost).

Thx

CHAZumaru

 

[TakaIsSilly]

Saturn technical question on KoF'95's cartridge

> WHAT is in the ROM cartridge of the game ?

My guess is as good as anyone's, but it's most likely graphics, read below

> What is stocked in it ?

Experience with damaged/wrong carts inserted in KOF'95 suggest that the ROM only contains graphics, most notably, the 2nd oppenent display. A good example seems to be the fact what with a 1MB ram cart, the 2nd player consists of gibberish.

> And why did they pick a ROM cartridge instead of a simple RAM extension (like they did afterwoods for obvious financial reasons) ?

It speeds up the loading process. Also, it prevents piracy.

> A programmer I know (who has no experience of the Saturn) made the hypothesis that there’s a DSP inside the ROM, like the Sega Virtua Processor in Virtua Racing for Megadrive/Genesis system.

> But the Yamaha SCSP DSP which serves as an link between the 68EC000 sound processor and the Audio-RAM would have been able to play that role, wouldn’t it ?

What's the need? KOF'95 is nice, but doesn't need extra CPU's...

>I know that textures and backgrounds are dealed by the VDP2 chip. Is the cartridge related somehow to the VDP2, giving him special access to the ROM information ? Therefore the disc information would be sent to the VDP1 and the the cart’s info to the VDP2 ? But then how come the ROM cart is only 1MB ?

Well, when he says "textures" he provably means sprites. The cart slot is a general purpose bus extensions, sort of like a ISA bus... If needed, or wanted,they can take precedence over parts of the memory... for example, booting their own BIOS like an AR does... This doesn't seem to be the case, but my memory tells me there is a bit of unused/reserved space just after the video memory that could be used by a cart... As for the size, most later releases still only used 1MB for extra data... 3Mb of WorkRAM + 512kb of VideoRAM (with fast DMA transfers) is quite a heap of memory for a 1995 console...

 

[printf]

Saturn technical question on KoF'95's cartridge

Originally posted by TakaIsSilly

The cart slot is a general purpose bus extensions, sort of like a ISA bus... If needed, or wanted,they can take precedence over parts of the memory... for example, booting their own BIOS like an AR does...

I don't understand what this means. The cart slot usually doesn't take precedence over anything, at least I haven't seen it do so with an AR inserted. The IPL (BIOS) of a Saturn has to check whether there is a cartridge in the slot, then hand over control. There are lots of pins on a cart for Saturn, but I don't think the SNK programmers would ever use all of these. DMA transfers from cartridge ram to video ram are slower than from work ram, right?

 

[TakaIsSilly]

Saturn technical question on KoF'95's cartridge

Originally posted by printf@Jan. 25 2003, 6:41 pm

I don't understand what this means. The cart slot usually doesn't take precedence over anything, at least I haven't seen it do so with an AR inserted. The IPL (BIOS) of a Saturn has to check whether there is a cartridge in the slot, then hand over control. There are lots of pins on a cart for Saturn, but I don't think the SNK programmers would ever use all of these. DMA transfers from cartridge ram to video ram are slower than from work ram, right?

I belive the carts can take precedence over certain memory adresses, after they're detected, altough I doubt this was ever used... also, don't the adress lines of the err... is it the B-Bus(I can't recall now) connect directly to the carts, and hence, the speed of memory in the carts the same as the remaing memory? maybe I should read up on the documentation, it's gaining digital dust in my PC ^^;

 

[antime]

Saturn technical question on KoF'95's cartridge

The cart port and CD system sit on the A-bus, the graphics and sound systems are connected to the B-bus. However, both CPUs, the main memory, the SMPC and the BIOS sit on the system bus. I really doubt the cart port can override the SCU, but I believe it could override the A-bus region and thus fool the BIOS to think there's data to be transferred from the CD system.

 

[AntiPasta]

Saturn technical question on KoF'95's cartridge

by the way, when you insert a RAM cart, where is the extra RAM mapped?

 

[antime]

Saturn technical question on KoF'95's cartridge

From 0x22480000 onwards, see technical bulletin #47 for details. (Note that as it's a "preliminary" version the details may not be entirely correct.)