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Anyone else use Defender Demo mode to test system (stress test)?


ACML

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I know it won't exercise the full 64K RAM, but the Demo mode on the Defender cartridge does a good job of exercising RAM, Sally, PIA, POKEY, GTIA and Antic. I run it in Demo for hours to see if anything overheats. A good way to test for chip health and AC to DC system on the 400/800 and 1200XL. Anyone else use something similar to stress the video, audio and CPU?

Edited by ACML
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When I was fixing my troublesome 1200XL last spring/summer, I used JOUST for the same reasons: very active demo/attract screen that tests all the major chips and memory. Worked very well and uncovered a latent bad GTIA once I got the machine to boot up again.

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The CPU is always 100% busy but I suppose a variety of instructions would generate more heat than a loop waiting on a flag change.

 

Antic/GTIA - the hires character mode with H-Scrolling as used would be fairly demanding + PM graphics adds a bit more but it's not full screen height.

Pokey - fairly standard sound just plugged during VBlank so not real demanding.

PIA - only reading joysticks during VBlank so not demanding. No bank switching going on.

 

But really one of the best ways to test your Atari is to just use it to do something which you've got going on here anyway. And much less boring than some cycling diag program.

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I just remember Defender was a great way to break space bars.

In my days of fixing Ataris, I've come across two 800's with broken spacebars. Defender was the "present and contributing factor" I'm sure. It breaks the solder joint on pad #57 on the Hi Tek keyboard. Anyone have a spacebar break that wasn't a Hi Tek?

Edited by ACML
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Star Raiders was a great test after recap and re regulator job on an 800.. The red alert screen on star raiders tests to see if the color bloom loss of focus issue is fixed. The screen should be able to go red to blue (with shields on) and not change the screen in focus or aspect ratio. You can actually steer the decelerating ship towards an enemy and bang them while the screen is red. :P

Using a luma chroma or composite output is best. Just replace the caps for 4700uf, 2200uf, 470uf, and 10uf and the 7805/7812.

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Not to derail the thread, but as a matter of habit I measure all caps on XL and XE boards that I come across with a good ESR meter....I have yet to find a SINGLE bad cap. I only have worked on my own PAL 800 and didn't check that one to be honest, which I will do next time I have it opened Up.

 

I have a simple theory why the XL/XE caps are still in good shape after about 30 years: they're pretty good quality to start with (although I would have loved it if Atari Consumer had stuck with Nichicon like Atari arcade division did) but the even more important factor is lack of heat. The A8 VLSI's are simply of great design and do not generate a lot of heat. The hottest chips are SALLY and ANTIC normally, but even those are not particularly hot. Heat is what kills caps.

 

I would be very interested in a dedicated stress test program that exercises all the chips to the max. It's great or have such a "burn-in" test program.

 

But Defender is pretty old-school and I think a lot of the more modern games probably require a lot more from the A8 hardware ?

 

Even Dropzone looks like more demanding to me if we'd like to keep it in the style of Defender.

Edited by Level42
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Antic is fetching graphics whether there's objects there or not. PMGs typically every scanline of the 240 visible. There's essentially no difference whether a character cell is all zeros or mixed pixels. GTIA much the same, the workload only differs really if there's PMGs in the mix.

 

A modern GPU might vary from room temperature + 5 degrees up to beyond boiling point but the Atari chipset once the machine is warmed up I doubt would vary by more than a couple of degrees for a chip busy vs idle.

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Even that stuff isn't much chop.

 

A true Antic/GTIA stress test would be full 240 scanlines, 48 column character mode with VScrol trick to force extra badlines. On non badlines, do reposition reuse of player objects.

Then you'd need it to look meaningful such that if malfunctions did occur it would be obvious.

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I've been running defender for 7hrs here and Altirra is still as cool as it was when it started.....

 

Yeah, rubbish joke...I'll get my coat....

 

Slight side, I seem to remember Avery talking about code in Altirra that emulates the warming of the Atari and its affects on components..(I'm sure I saw something about that from him)

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Known temperature sensitive items -

 

- GTIA: mode 10 pixels can shift 1/2 pixel to the right (rumoured but tested without success so either rare or untrue).

- GTIA: 5th player enable can sometimes show a single cycle artifact.

 

- POKEY: IRQ signalling can vary by 1 cycle http://atariage.com/forums/topic/168218-pokey-serial-and-irq-timing-details/?do=findComment&comment=2081463

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Known temperature sensitive items -

 

- GTIA: mode 10 pixels can shift 1/2 pixel to the right (rumoured but tested without success so either rare or untrue).

- GTIA: 5th player enable can sometimes show a single cycle artifact.

 

- POKEY: IRQ signalling can vary by 1 cycle http://atariage.com/forums/topic/168218-pokey-serial-and-irq-timing-details/?do=findComment&comment=2081463

Stuff like that could also be depending on manufacturer of the chip and even batches....

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