exxos's Atari, Amiga & retro forum

OK, so the Syscheck arrived yesterday, very impressed since it was only posted on Sunday and came from Germany.

I did run some tests, which are pointing at the RAM, but I'm going to need to read the manual properly and possibly ask Jurgen about what I'm seeing since he clearly has a great deal of expertise.

More to follow...

Let's hope that it shows the way to a fix.

stephen_usher wrote: 10 Mar 2022 09:24 Let's hope that it shows the way to a fix.

I do hope so.

What sort of output does that diag cartridge give? Is it a dead-test-alike flashing screen or some sort of text?

stephen_usher wrote: 10 Mar 2022 09:42 What sort of output does that diag cartridge give? Is it a dead-test-alike flashing screen or some sort of text?

It is effectively a dead test, it'll run even if the machine has no RAM installed. It runs a RAM test on boot and then a ROM test, but mine is failing at the RAM test, BUT I don't know if that is because it's a 64KB 600XL, so need to read through the notes again and ask Jurgen. After that, it's supposed to run a ROM test but doesn't get that far.

The RAM test fails after 16KB, but the black screen I get on boot without the Syscheck also suggests the zero page RAM is bad because the OS has no RAM to use.

rubber_jonnie wrote: 07 Mar 2022 19:12 I'm not familiar with the OS internals, but I do have a copy of Mapping the Atari and I'm wondering if it can give me some clues as to the boot process.

Mapping The Atari is a great book, but for tracing the OS, the OS source would probably be more useful. It is available here:
https://atariwiki.org/wiki/Wiki.jsp?pag ... gSystemsOS

It is effectively a dead test, it'll run even if the machine has no RAM installed. It runs a RAM test on boot and then a ROM test, but mine is failing at the RAM test, BUT I don't know if that is because it's a 64KB 600XL,

No, an upgraded 600XL is the same as an 800XL. Something is wrong with RAM access. Of course, it doesn't necessarily have to be a RAM chip itself.

If it's potentially a RAM issue and you've done modifications to the RAM then maybe returning the machine to stock might be a good idea, just to get a baseline?

ijor wrote: 10 Mar 2022 13:45

rubber_jonnie wrote: 07 Mar 2022 19:12 I'm not familiar with the OS internals, but I do have a copy of Mapping the Atari and I'm wondering if it can give me some clues as to the boot process.

Mapping The Atari is a great book, but for tracing the OS, the OS source would probably be more useful. It is available here:
https://atariwiki.org/wiki/Wiki.jsp?pag ... gSystemsOS

It is effectively a dead test, it'll run even if the machine has no RAM installed. It runs a RAM test on boot and then a ROM test, but mine is failing at the RAM test, BUT I don't know if that is because it's a 64KB 600XL,

No, an upgraded 600XL is the same as an 800XL. Something is wrong with RAM access. Of course, it doesn't necessarily have to be a RAM chip itself.

Ok, so that's interesting. @ijor So even with the 2 chip 64KB upgrade, that should be seen much the same as an 800XL?

By booting the OS off the Syscheck card, but using the Atari RAM, I can hold OPTION down and get the memory test, which fails after 16KB. If I don't hold OPTION down I get a black screen.

By booting with no Syscheck, so all 600XL RAM & ROM, I can hold OPTION down and get the memory test, which fails after 16KB. If I don't hold OPTION down I get a black screen.

By booting to Syscheck, using Syscheck RAM & ROM, I can hold OPTION down and get the memory test, which passes fully for 48KB. If I don't hold OPTION down I get a blue screen with a cursor top left (Normal OS boot behaviour) that drops to the full Self Test menu.

So it seems like it has got to be RAM, everything is pointing that direction. Since I know the MMU and all the logic ICs are good (LS ICs are new, the main ICs were tested in my 800XL) it suggests there is possibly a physical problem on the board.

stephen_usher wrote: 10 Mar 2022 14:31 If it's potentially a RAM issue and you've done modifications to the RAM then maybe returning the machine to stock might be a good idea, just to get a baseline?

I returned it to stock and it won't even run Star Raiders. It could be faulty RAM, but it could also be something else.

rubber_jonnie wrote: 10 Mar 2022 14:57

stephen_usher wrote: 10 Mar 2022 14:31 If it's potentially a RAM issue and you've done modifications to the RAM then maybe returning the machine to stock might be a good idea, just to get a baseline?

I returned it to stock and it won't even run Star Raiders. It could be faulty RAM, but it could also be something else.

I'd still return it to stock and then use the diagnostic cartridge. Being able to Star Raiders with expansion may be taking you on a wild goose chase where it's using RAM that the rest of the system can't see or use initially.