exxos's Atari, Amiga & retro forum

After reading both

exxos wrote: 28 Sep 2018 08:20 you lift the MMU end up of those resistors and then tie the free ends to 5V.

and

rubber_jonnie wrote: 28 Sep 2018 08:22 If I recall, if you are leaving the RAM chips in, you'll need to de-solder the bottom end of those 3 resistors and connect them to +5v to disable that second bank of 512KB RAM, a bit like if you added a Marpet or similar RAM add on.

Double check this before you do it though in case I'm remembering it wrong.

I think the double check was done for me already ;-)

sandord wrote: 28 Sep 2018 14:15 I think the double check was done for me already ;-)

Yeah, I reckon so :)

I think we wrote our replies at almost the same time.

It's running with 512kb right now, so far I don't see any problems.

I guess the only practical way of fixing this ST (besides leaving it crippled with 512kb) is upgrading it with a RAM kit.
Replacing the darn j-leaded RAM chips looks pretty much impossible to me.

Well, there they are again (running with 512kb).

http://www.exxosforum.co.uk/atari/last/4mb/RAMTEST.zip

You could try the marpet one, I know that tests screen RAM, but tests are not as good as YAART.. but worth a try...

- with 1mb, I get rogue pixels GemBench at the bottom of the screen
(video address is near the top end of the RAM)
- with 1mb, I get rogue pixels in Metrocross at the bottom of the screen
(not sure where the video address is in this game)
- with 512kb, I get rogue pixels in GemBench at the bottom of the screen
(video address is near the top end of the RAM)
- with 512kb, I get rogue pixels in Metrocross
(not sure where the video address is in this game)
- I've seen YAART detect a memory error only once out of quite a few runs.
- With 1mb, I've seen YAART show rogue pixels in between the status text quite a lot but it never detected a memory error. Looks like YAART doesn't test the RAM where the status text is rendered to?

Looks like a pattern to me, problems appear to be at the end of each bank only. Too much of a coincidence?

Will try RAMTEST now...

sandord wrote: 28 Sep 2018 15:07 Looks like YAART doesn't test the RAM where the status text is rendered to?

I've sent a PM to czietz (YAART creator) and asked him about it.. just have to wait until he next logs in...

exxos wrote: 28 Sep 2018 15:12 I've sent a PM to czietz (YAART creator) and asked him about it.. just have to wait until he next logs in...

Thanks!

RAMTEST says 171 OK passes, 0 fails.

sandord wrote: 28 Sep 2018 14:58 Well, there they are again (running with 512kb).

IMG_20180928_155451.jpg

I saw strange patterns show up in some sprites as well, which were located around the vertical center of the screen.