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2012-03-27 07:19

Repose

Registered: Oct 2010
Posts: 222

Access 32k of SuperSnapshot

Hi,
Does anyone know how to access the 32ram bank of a supersnapshot cartridge? I've upgraded mine from 8k(?). I used to know, I think you had to make some writes to invisible registers to put it in some kind of MAX mode and then copy or access the ram from there, but the 32k even has a banking system.
Also is there a rom dump available. I actually wrote some of the code but it was modified after it left my hands, it would be interesting to see what's in the final version.

2012-03-27 07:44

chatGPZ

Registered: Dec 2001
Posts: 11136

looks here: http://rr.pokefinder.org/wiki/Super_Snapshot

2012-03-27 18:07

Repose

Registered: Oct 2010
Posts: 222

That's an awesome page! Thanks. It seems if you load the .crt file into Vice, it works.
I did a quick test and came up with this:
* =$33c
sei
lda #0
sta $de00
ldy $03
lda $02
bne $350
ldy $8000
sty $03
lda #1
sta $de00
cli
rts

10ml=828
20dr=2
30dt=3
40pokedr,0
50sysml
60m=peek(dt)
70print"Read byte from $8000 SS RAM";m

I went on to prove I could have different bytes than c64 ram at that address. The 4 banks of 8k are switched in to $8000-$9fff, and controlled by these values to $de00:
bank 0:$00
bank 1:$04
bank 2:$10
bank 4:$14
But this is untested on real hardware as of yet. When you access the ram, you are in Ultimax mode, which means the computer is practically empty except for C64 ram appearing under $1000.
To test the ram size, you'll have to write test values to the same spot in each bank, and see if you can read them back. If you discover mirroring in some banks, there's less ram.
$01 returns you to normal mode (with snapshot enabled).

2012-03-28 21:07

Skoe
Account closed

Registered: Jan 2008
Posts: 34

Repose,

So you play with original SS5 hardware and you seem to have some background about this cartridge. Great :)

If you have any test program and know the expected results, it would be nice if you could share it. I implemented an SS5 mode on EasyFlash 3 and would like to know if everything is correct. The cartridge ROM seems to work, that's all I know up to now :)

2012-03-29 09:21

Repose

Registered: Oct 2010
Posts: 222

Hello,
Your page was interesting - nice project! However, I could find no documentation on how the cart is accessing. Could you post details of the registers?

I just got cbm program studio and it's quite nice! This is encouraging me to write a ramdisk driver for the SS or any other ram expander. Nothing as fancy as the REU driver, that would be too big a project.

I can see your hardware as being a type of permanent harddrive, in fact the SS ROM features an autoboot after 30 seconds, so we could have an autoboot from permanent flash system. I can see the C= as being a nice solution for monitor/control applications, instead of using an Arduino etc. Just a thought anyhow!

Mostly I've always wanted to write a cartridge detector which doesn't make POKE's in a way to crash any known device. I did once write such a system to test the SID Symphony cart without causing a crash due to an REU being present, or in fact an SS. It was sold to Dr. Evil Labs for internal quality control.

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