Saturn Internal SRAM mods

[gc8tech]

Hello all,

This is the end of a project to expand the onboard SRAM for saves. I was hopeing to get the BIOS modded to add the extra 2 address lines and show a total of 1024kbit of sram instead of just 256kbit....

I emailed the guy that did the region free bios... But never got a reply. So i decided to re-do the project and make 4 pages of 256K instead. I had to learn to program a PIC... which i wanted it to do the bank / page switching. I had never programed a PIC before... but i can see why they are used so much.

I modded the green power led to a bi colour red/green (orange). When the led goes orange.. you are at page 00. That way if you get lost pressing the reset button.. just keep doing it till the led goes orange.

Reset button counts up the pages.

It works great.. i just wish the cdrom drive worked as well :-P I have no idea if anyone would do this mod due to save carts... But the slots can get a bit "loose".. You could also use a 2048kbit chip instead and have 8 pages instead of 4. I'd have to reprogram the chip and add an extra address line.

D.

[buckoa51]

Interesting work. Rather than trying to increase onboard save memory, A mod to replace the Saturns onboard backup memory with something that doesn't die every other month because your battery has been exhausted would be of very significant value.

[gc8tech]

Yes.. you can use (ramtron) FRAM... it doesn't need power to store data. BUT it very hard to find it in a 1024kbit... OR the needed SOP package.(It maybe easyer to find in a 2048kbit instead)
BUT you can change the RTC / SAVE battery to a 4.5V battery WITHOUT mods to the saturn. The Schmatics i found show its fine. The same circuit has 5V going though it when the Saturn is turned on. So aslong at the BATT voltage is less than 5V.. its fine. I was thinking 3 X AA batterys. I had not finshed this mod yet... But it was the next to follow this mod.