Incognito Instability

[Xuel]

My NTSC Atari 800 with Incognito appears to be unstable. It works fine on some programs but crashes on others. Sometimes it works for a while and then crashes. I tried removing the Incognito and putting back the original OS and RAM boards and it appears to work fine. Any advice on how to go about debugging it?

 

Things that work:

 

Self-Test - all memory passes

Acid800 - all tests pass

XRAM - all extended memory passes

Incognito menu - I can set options, save and cold start. It also comes up fine after a crash

 

Things that work with original boards but not Incognito:

 

The Hunt - boots to various degrees and then crashes, or crashes after several minutes

Joust - crashes after several minutes

Atari Dealer Demo - same

Donkey Kong - same

 

When it crashes, it seems like ANTIC and GTIA are still functioning but the display is corrupted when there DLIs and VBIs in play. So perhaps the CPU is unstable or there is memory corruption?

 

I tried swapping the ANTIC with an 800XL and saw no change. I tried swapping the 6502 as well, but it didn't work at all, probably because HALT needs to be deasserted on a 6502C. Is there an easy way to use a 6502C in an 800?

 

 

[candle]

try tapping the board while it works

if that would trigger the crash, let me know

you may want to clean incognito's edge connector with some kind of solvent - acetone or isoprophyl alcohol - if that would be the reason of such behaviour it should cure it

this is board from last run or it something that developed recently?

[Xuel]

Thanks! I'll try those suggestions when I get home. This is the board you just sent me from batch #3. I just installed it last weekend and noticed the instability then. I tried reverting and reinstalling today. I'll let you know.

[+tf_hh]

Hi,

 

My NTSC Atari 800 with Incognito appears to be unstable. It works fine on some programs but crashes on others. Sometimes it works for a while and then crashes. I tried removing the Incognito and putting back the original OS and RAM boards and it appears to work fine. Any advice on how to go about debugging it?

 

[...]

 

I tried swapping the ANTIC with an 800XL and saw no change. I tried swapping the 6502 as well, but it didn't work at all, probably because HALT needs to be deasserted on a 6502C. Is there an easy way to use a 6502C in an 800?

 

Just two hints... if you have a Happy 1050 (clone) anywhere, they have a 6502B CPU mostly on board. You can use it for testing.

 

But I prefer to clean all connectors first. I´ve built a lot of Incognitos into 800 computers and when there were trouble, mostly it depends on bad contacts. Detach the CPU board, clean the contacts with a rubber. The edge connector itself should be cleaned with a toothbrush or with some folded clean, white paper. Move it up and down into the space between the contact guides, never left to right, only up and down. Repeat this also to the personality slot connector (where the Incognito is plugged in).

 

Also try (this is not a cure-all, but in two cases it had helped me) changing the both 74LS243 ICs to another one.

 

BR, Juergen