exxos's Atari, Amiga & retro forum

So turned it on this morning, its been running almost 3 hours and at loop 47.. probably would have reached around loop 60 at 40mhz.. In anycase, its been pushing to run 15mins before... So I'm not going to touch a thing and leave it running see what happens...

If it still running later, I will bash it about a bit see if it stops working...

exxos wrote: ↑Thu Jul 19, 2018 10:47 am So turned it on this morning, its been running almost 3 hours and at loop 47.. probably would have reached around loop 60 at 40mhz.. In anycase, its been pushing to run 15mins before... So I'm not going to touch a thing and leave it running see what happens...

If it still running later, I will bash it about a bit see if it stops working...

The inconsistency is very strange...

rubber_jonnie wrote: ↑Thu Jul 19, 2018 11:33 am The inconsistency is very strange...

Got to loop 58, so 3.5 hours.. reset it and see what I get this time...

EDIT:

About loop 30 that time.. hard to keep a eye on it, so I updated GB6 to output the count to file so I don't have to keep a close eye on it..

I smacked it about, and didn't crash.. Just leaving it running to see what number it gets to this time...

LOOP 34 that time.. onto the next testing..

LOOP 18 65mins run time.. 36.5C (floppy 28C)

LOOP 55 33C (floppy 27C)

I'm going to start monitoring the CPU temp.. just find it odd as the day goes on and gets hotter the CPU is failing more.. but still doesn't explain why it failed in the morning when its coolest anyway.. I will take the floppy drive case as "ambient temp".

EDIT:

OK its almost like cooler temps running for longer, but will put back the 40MHz osc and I will try not to move the PCB at all...

EDIT2:

Something odd I found earlier, the OSC itself is listed as a 3.3V one.. BUT, it didn't run on 3.3V on my previous board, so thought its a 5V one and used that.. Later removed the 3.3V regulator and just ran direct to 5V... Though looking at the datasheets its a 3.3V part, so no idea why it wouldn't run on 5V before.. but its possible the OSC itself could be crapping out... So I have ordered some various 5V speed OSCs..

EDIT3

40MHz tests

16mins 16 loops - 36.5C CPU, 27c floppy case. (just went to desktop, no bombs, locked up)
92mins 30 loops - 37c CPU
13mins 5 loops - 34c CPU (even put heatsink on OSC)
60mins 20 loops - 34c CPU
222mins 71 loops - 37c CPU - 40c OSC - 39c GAL - 26c floppy case (feels a lot cooler in my room today)

Seems like temperature goes up the longer its running, which makes sense. But don't think has any relation to it crashing. I get similar with 25MHz so don't think this a CPU itself problem.

I've been updating the above post.. 3.7hours it ran today..

Got my proper 5V oscs and now it "quits to desktop" after a few test loops.. So maybe this is a clue.. Will investigate...

5V OSC
3.3V OSC Not much between them.

5V has slightly lower DC offset. 3.88V - 0.72V = 3.16V P-P.

3.3V OSC is 4.2V - 0.92V = 3.28V P-P.

Pretty much could put it down to tollerences.

I do have problems with 40MHz on the CPU buffer though as the clock is going so fast (40MHz) it hardly goes down to 1V for logic low levels. But the buffer thankfully clears all that up.

The GAL datasheet says 0.8V max for logic low level. So you would think the 3.3V one would be worse (930mV) but that one works the best.
Logic HI is >2V so assume no problem there.

I'm thinking the GAL needs a buffer also now.. I will see if I can remove the DC offset more on the 5V one and see if it helps or not...

Freezer spray turned up

Been spraying the 5V OSC and the min/max is about 640mV 4.00V (was 720mV 3.88V)... it run 3 full cycles, then crashed while I was trying this.. before without the spray it crashed pretty much right away..

So how it looks currently is crappy tolerances on the OSC chips

Now I have a cap in series with the 40MHz OSC... DC offset gone.. made no difference

So will try increasing the DC offset as that is what is hinted in my previous scope images.. even though GAL spec wise it shouldn't work at all...


Current mash up...


So far it locked up on the last GB6 test.. but will keeping doing more testing...

Second pass it crashed on first test... I adjusted the DC offset to match the 3.3V one.. still crashed on first test

EDIT:
So spraying the whole board with freezer spray seems to make it more stable... its passed all loops 4 times after spraying the thing... and yet even 25MHz which is half the speed still refuses to work, so its not like its overheating from the raw MHz on the GAL or CPU.

Will add a few pF onto the OSC output.. see if that helps.. Actually had to do that on the GAL output...

The magic world of electronics!

dhedberg wrote: ↑Fri Jul 20, 2018 8:16 pm The magic world of electronics!

Indeed! I need a easier hobby! Then people wonder why I don't wake up one morning and slap on fast-ram, fast-tos, flash rom, ide all at once..