Saturn Backup Memory Cartridge, 670-6415A

R

RDC

Member
The Sega Saturn Backup Memory cartridge, 670-6415A. It's only used for game saves, versus saving them on the smaller internal memory of the Saturn, that can be lost if the power is removed and the internal battery dies. This Backup Memory cart is flash based, so the saves stay intact when the power is removed, and it has over 17 times the save space versus the internal memory.

TOP


BOTTOM


TOP CLEAN


SCHEMATIC



IC1 - AT29C040A 15TC (150ns)
IC2 - 74HC00A
IC3 - 74HC244A
CE1 - 16v, 47uF
C1, C2, C3 - Decoupling, could be anything from 0.01uF to 1uF each

IC1 must be an AT29C040A (150ns or faster) or the Saturn will not recognize it. It also seems to need to have the Boot Block data present, as I had issues getting another 29C040A 12TC (120ns) to work correctly (Saturn would detect it, but not Clear it) until it was flashed with a dump of the original 29C040A chip. I went thru a fiasco with some rebranded 29LV040A chips (branded as 29C040A) that would not work even with the correct Boot Block Data on them. The Saturn seems to check the Device Code of the chip before proceeding, and since the 29LV is 0xC4 and the 29C is 0xA4, it would have none of that.

Code: 
Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00000000 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000010 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000020 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000030 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000040 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000050 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000060 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000070 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000080 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000090 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
000000A0 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
000000B0 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
000000C0 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
000000D0 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
000000E0 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
000000F0 42 61 63 6B 55 70 52 61 6D 20 46 6F 72 6D 61 74  BackUpRam Format
00000100 00 00 00 00 00 00 00 00 00 00 04 00 00 00 00 00  BackUpRam Format

I've also designed a smaller PCB of this, though not quite small enough for the cartridge flap to close when it's inserted, but for it's intended purpose it doesn't need to.





 
On the Sega CD Backup RAM Cart there is a 74HC244 used to indicate the size of the cart to the console. I noticed on here the 74HC244 is hardwired to output 0x01. Did you experiment with other values on here to see if the console would "think" it had a larger memory cart? I experimented with this on Sega CD and managed to produce the largest allowed Backup RAM Cart which is 512KB (x4 from the original 128K).

You can check out the very bottom of this page on my website for a quick description of the memory of the Sega CD Backup RAM Cart.

Since 512K on the Sega Saturn Memory Cart seems to be indicated by 0x01, I think it would be safe to assume that valid cart sizes go up in 512K increments. It would be interesting to try this out!
 
Thanks.

I didn't get into mucking around with the workings of it as it was mainly just being reversed on the hardware level to make it smaller for a project while still using the original components.


Interesting site, might want to consider giving reference credits when using others scans/pics, or take the time and effort to make your own.
 
RDC said:
Interesting site, might want to consider giving reference credits when using others scans/pics, or take the time and effort to make your own.
Click to expand...

Added reference and credit where required; didn't realize it would be an issue. When I post on internet forums I kind of assume the information I give out is out of my control from that point on, else I wouldn't post it. I try to collect as much info as I can and centralize it on my site for ease of reference.

I already had reversed engineered some of that info on my own as well and am in process of building my own. My main roadblock is the pricing and availability of AT29C040 - there's sources on eBay and other various Chinese sellers but I'm not sure I want to commit to that kind of stock.
 
If you prefer passing off the work others put into things as your own that's your business, just know I wouldn't use anything you actually put the time and effort into and pretend it was mine. Internet or not, there's nothing wrong with giving credit where it's due.

Make sure your supplier actually has the 29C chips, you don't want to order a pile of rebranded crap like I ended up with when I went looking for those things. They were all branded 29C on the outside and looked perfectly legit, but the programmer detected them all as 29LV and the Saturn didn't care for them at all.
 
No, you did say it was your website though, and there's no mention of where this or that info on there came from, so anyone looking at your site is supposed to assume what?

You gave credit for where the image/info came from, and that's all there was to it, didn't kill you to add that in there at all and that's all there should be to it.
 
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