SNES cart with RAM banks

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Oziphantom
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SNES cart with RAM banks

Post by Oziphantom » Thu Aug 15, 2019 11:31 pm

Is it possible to make a SNES cart that has RAM mapped to the ROM banks, HiROM style. This way you can get FAST RAM, and put code into RAM? Or does the SNES force R/W to R when asserting /CART ?

lidnariq
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Re: SNES cart with RAM banks

Post by lidnariq » Thu Aug 15, 2019 11:41 pm

/CART (or /ROMSEL, whatever you want to call it) is just a function of A23-A17 and A15.

"LoROM" games with RAM in bank $70 can access their RAM at 3.6MHz (in bank $F0)

Oziphantom
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Re: SNES cart with RAM banks

Post by Oziphantom » Fri Aug 16, 2019 2:29 am

yes but that is the SRAM which is broken up into small chunks. I'm not talking about making SRAM but putting RAM banks as in whole 64K bank at for arguments sake E0:0000-E0:FFFF.

lidnariq
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Re: SNES cart with RAM banks

Post by lidnariq » Fri Aug 16, 2019 10:21 am

I mean, the anecdote is just pointing out that you can already get it on existing hardware, just not "Very Large" RAM. But "Very Large" RAM is extremely rare on contemporary hardware regardless of PCB, so it's not much of a constraint.

The /RD and /WR strobes don't do anything funny based on address, other than the funniness during DMA.

Revenant
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Re: SNES cart with RAM banks

Post by Revenant » Fri Aug 16, 2019 12:38 pm

Oziphantom wrote:Is it possible to make a SNES cart that has RAM mapped to the ROM banks, HiROM style. This way you can get FAST RAM, and put code into RAM? Or does the SNES force R/W to R when asserting /CART ?
Believe it or not, Nintendo did it already!

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