32MB RAM upgrade

[tsowell]

Hi everyone,

I upgraded my Dreamcast's system SDRAM to 32MB last week. I've written an explanation of how the mod works and instructions for doing it: https://tsowell.github.io/2020/06/21/dr ... grade.html

Unfortunately because of the equipment and soldering experience required it might not be within everyone's reach, but I hope someone can benefit from this.

I've been using the extra RAM with my alternate ScummVM backend (Dreamcast-talk discussion here), and so far I've been able to use it to run a few ScummVM games that run out of memory and crash on a 16MB Dreamcast.

Given that software needs to be modified to take advantage of the extra RAM, are there any other potential uses for this? Maybe other homebrew or emulators that are being held back by the 16MB limit?

[Ian Micheal]

For sure quake engines ports of dukenukem and quake 2 decent etc quake 2 being one for sure

[mrneo240]

my poor quake2 port

[Ian Micheal]

my poor quake2 port

Be cool to see it work on his rig yeah nice

[|darc|]

Thanks for this -- pretty cool stuff. I ordered some of that SDRAM so I can give this a shot.

EDIT: Regarding hex-editing the BIOS, you gave instructions for japanese-cake 1.032 but that BIOS has some incompatibilities and so I don't use it. The bytes you suggest to replace at 0x5070 don't exist there on all other BIOSs, but do exist at 0x70. I assume this is the correct part to patch instead?

[tsowell]

Thanks for this -- pretty cool stuff. I ordered some of that SDRAM so I can give this a shot.

EDIT: Regarding hex-editing the BIOS, you gave instructions for japanese-cake 1.032 but that BIOS has some incompatibilities and so I don't use it. The bytes you suggest to replace at 0x5070 don't exist there on all other BIOSs, but do exist at 0x70. I assume this is the correct part to patch instead?

Yes, that's correct. The SEGA BIOS I looked at loaded them from 0x70. I understand there's a BIOS integrity check that your BIOS will need to circumvent, but I imagine any hacked BIOS will already be ready to be modified.

[zychion]

This may seem a little uneducated and probably a little early but from your instructions it sounds like we could attach a switch to the mod much like we do on the piggy back bios method. Having wires connected to pin 21, 22 with a couple resistors so that you could switch on 32mb and switch it off as to have the original bios boot still. Again I understand that this is probably a bit premature.

[fafadou]

I'm thinking about TOM JAM & EARL 3 at the end of th game there are memory issue because of the too huge map at the last levels.

Many thanks to share this fabulous mod

[Anonymouse]

absolutely amazing stuff. what was the total cost of this?

[tsowell]

absolutely amazing stuff. what was the total cost of this?

12.66 USD for two IS42S32800J-6TLs. A lot cheaper than the NAOMI I was considering.