6502 gone dead. but why?

[RodCastler]

I have a very nice 130XE within my collection.

After a couple of years without touching it I brought it out for a spin this week. Only to find a red screen.

 

Since fine vertical strips came on first at every power up before the red screen, I suspected something going wrong with MMU or addressing.

Brought the scope out, and showed activity at the address bus but nothing at all on the data bus.

 

I de-soldered the CPU and soldered a socket in its place, then tested with a spare 6502 CPU from an 800XL and all was good again. Memory test on the 130XE went fine after that, it was definitely the 6502.

 

Question is why did the main CPU die all of the sudden? Is this common?

 

- I've been using good power supplies, no ingots, and I remember last time this machine was working perfectly fine. It was just stored in a dry environment for a couple of years...

Edited August 8, 2015 by RodCastler

[Bryan]

It could be impurities in the die that lead to breakdown of some connection somewhere.

[JamesD]

It wanted to!
But seriously, there are any number of reasons. Moisture could have gotten inside, vibration, a cosmic particle might have hit it in just the right spot...
It's kinda like trying to figure out how many licks it takes to get to the center of a Tootsie Pop... the world may never know.

[RodCastler]

Yes, that sounds about right.

It's just that I always thought the RAM chips were the weakest point and they may die out of nothing.

 

This lead me to think the other chips were rock solid unless you did something really wrong with voltage. I guess it was not the case.

[AtariLeaf]

It's kinda like trying to figure out how many licks it takes to get to the center of a Tootsie Pop... the world may never know.

 

But we DO know. It's three!

[+bob1200xl]

Did you try the original CPU again? Soldering in a socket may have resolved your problem.

 

If the CPU itself really did go bad, it may be mechanical - dis-similar metals that expand at different rates finally losing contact. So, from the last time you used it the joint fractured.

 

There isn't much in the silicon structure that goes bad. Static discharge, maybe. You build up a charge walking across the roon and then touch the SIO pins when you pick up your Atari.

 

Who knows?

 

Bob

 

 

 

I have a very nice 130XE within my collection.

After a couple of years without touching it I brought it out for a spin this week. Only to find a red screen.

 

Since fine vertical strips came on first at every power up before the red screen, I suspected something going wrong with MMU or addressing.

Brought the scope out, and showed activity at the address bus but nothing at all on the data bus.

 

I de-soldered the CPU and soldered a socket in its place, then tested with a spare 6502 CPU from an 800XL and all was good again. Memory test on the 130XE went fine after that, it was definitely the 6502.

 

Question is why did the main CPU die all of the sudden? Is this common?

 

- I've been using good power supplies, no ingots, and I remember last time this machine was working perfectly fine. It was just stored in a dry environment for a couple of years...

[JamesD]

But we DO know. It's three!

I think there was a flaw in that test methodology.

[1050]

After 30+ years you can really say all of a sudden? They go when they go and I've had them go too and no other reason but it was their time to go. Won't say it's common by any means, but made in mexico happens enough times with the 6502 to have been noticed before. My single case was, printed right on the chip too.

 

They may all die from nothing, RAM chips are only very much more sensitive to over voltage situation so much so they are our safety valves and blessing at the same time. A lot of talk about bad types of RAM where in my case, several machines with those work fine and always have. Have had far more 6520 PIA's on 800 lay down and quit working.

[+Ransom]

Haven't you heard? There's this part of the 6502 chip that makes them fail after a certain amount of time.

[Bryan]

Haven't you heard? There's this part of the 6502 chip that makes them fail after a certain amount of time.

That's what Popular Mechanics magazine says and they're rarely wrong about this sort of thing!

[JamesD]

Haven't you heard? There's this part of the 6502 chip that makes them fail after a certain amount of time.

HP must use that part in their laptops and printers.

[RodCastler]

After 30+ years you can really say all of a sudden? They go when they go and I've had them go too and no other reason but it was their time to go. Won't say it's common by any means, but made in mexico happens enough times with the 6502 to have been noticed before. My single case was, printed right on the chip too.

 

They may all die from nothing, RAM chips are only very much more sensitive to over voltage situation so much so they are our safety valves and blessing at the same time. A lot of talk about bad types of RAM where in my case, several machines with those work fine and always have. Have had far more 6520 PIA's on 800 lay down and quit working.

 

With "all of the sudden" I mean without any external user-induced circumstances being involved.

 

And what I've read in this post is the information I needed, concluding that they all may just die even while in storage.

This particular one is an NCR made in Korea (C014806C-29).

 

thanks everyone!

[Bryan]

By the way, we've been poking fun at this thread in here. Enjoy!

[RodCastler]

After acknowledging the potential catastrophic failure on any 6502, my next thought was how do they trust these chips for space missions?

 

Well, of course they just don't and I found an interesting article that mentions:

 

"Since the computers are essential, NASA decided to use five identical computers in operation for critical periods like launch and landing. Four of the units operate together, and if one has a different result, it's presumed wrong and is "outvoted." The fifth computer is programmed separately from the other four and acts as a backup to prevent possible generic software errors from causing problems. In addition, an offline spare--a sixth GPC--is carried, which can be swapped with a malfunctioning GPC in orbit if necessary."

 

Interesting facts are my thing, I thought of sharing...

[RodCastler]

And yes, I just gave you yet another good reason to own at least 5 Atari computers! Feel free to blame NASA next time your significant other asks about that stack of yours.

Edited August 21, 2015 by RodCastler

[+Firedawg]

After acknowledging the potential catastrophic failure on any 6502, my next thought was how do they trust these chips for space missions?

 

Well, of course they just don't and I found an interesting article that mentions:

 

"Since the computers are essential, NASA decided to use five identical computers in operation for critical periods like launch and landing. Four of the units operate together, and if one has a different result, it's presumed wrong and is "outvoted." The fifth computer is programmed separately from the other four and acts as a backup to prevent possible generic software errors from causing problems. In addition, an offline spare--a sixth GPC--is carried, which can be swapped with a malfunctioning GPC in orbit if necessary."

 

Interesting facts are my thing, I thought of sharing...

I guess using remote terminal or the "Cloud" is out of the question?

 

Mike

[R.Cade]

You have to consider the power supply and everything else on the board that connects to the CPU in this scenario. Capacitors are known for aging and not working to spec anymore, and they control the voltages to the CPU. To say the CPU died on it's own *could* happen, but there are a lot of variables. As soon as you turned it on, a hundred old electronic components started up at once and if any of them are out of spec now, well...

 

But yes, the CMOS/NMOS process wasn't designed to make chips that last forever. We all eventually fail from old age/oxidation.

Edited August 21, 2015 by R.Cade

[Zonie]

It was made in a dirty fab...

[Keatah]

Whisker growth and metal migration.

 

http://www.corfin.com/resources/tin-whiskers/

https://en.m.wikipedia.org/wiki/Whisker_(metallurgy)#

http://nepp.nasa.gov/whisker/

Edited August 24, 2015 by Keatah

[+mytek]

Did you try the original CPU again? Soldering in a socket may have resolved your problem.

 

If the CPU itself really did go bad, it may be mechanical - dis-similar metals that expand at different rates finally losing contact. So, from the last time you used it the joint fractured.

 

There isn't much in the silicon structure that goes bad. Static discharge, maybe. You build up a charge walking across the roon and then touch the SIO pins when you pick up your Atari.

 

Who knows?

 

Bob

 

 

 

 

You know Bob made a good point here. So did you try the original CPU again? Pretty easy to do now that it's socketed. Be kinda a shame to throw it away if it's still good.

 

- Michael

Edited August 24, 2015 by mytekcontrols

[RodCastler]

Oh, by all means.

 

I am incapable of throwing these away even knowing they are not working.

First thing I did after removing the chip was to try it on two other working motherboards and saw the exact same symptom. That's why I knew for sure it was the 6502.

 

I later went to a friend's house who offered some spare Atari 6502's. He wanted to test them on his 800XL before I left, and interestingly enough, three out of the five he had turned out to be as dead as mine.

 

Thanks!

 

 

 

So did you try the original CPU again? Pretty easy to do now that it's socketed. Be kinda a shame to throw it away if it's still good.

 

 

[+mytek]

Oh, by all means.

 

I am incapable of throwing these away even knowing they are not working.

First thing I did after removing the chip was to try it on two other working motherboards and saw the exact same symptom. That's why I knew for sure it was the 6502.

 

I later went to a friend's house who offered some spare Atari 6502's. He wanted to test them on his 800XL before I left, and interestingly enough, three out of the five he had turned out to be as dead as mine.

 

Thanks!

 

 

 

Cool. Just wanted to verify that you retested it, which you did.

 

Also about your friends 6502's, keep in mind that some of the ones used in the very early 400/800 series were different than what is used in a 800XL. On the original first run 400/800 CPU boards they used a standard 6502, but then later they went to a custom version (6502C) that had an enable line, which allowed them to get rid of 4 support chips (for shared Antic DMA). So if some of your friend's chips were a standard 6502, then there is no way that they would work in your 800XL.

 

Quote from Wikipedia Atari 8-Bit Family page...

"Atari also ordered a custom version of the 6502, initially labeled "6502C" but eventually known as SALLY to differentiate it from a standard 6502C, which added a single pin that allowed four support chips to be removed. The SALLY was incorporated into late-production 400/800 machines, all subsequent XL/XE machines and the Atari 5200 and 7800 game systems."

 

 

- Michael

Edited August 24, 2015 by mytekcontrols

[Zonie]

Material breakdown within the die. Contaminants can kill a chip but it can take years. A tiny droplet from blinking or talking while the die was somewhere in the process is all it takes. Either causes a short or corrosion opens a circuit.

 

It's why we wear this crap. Doesn't help that I didn't button the top button!

 

Edited August 25, 2015 by Zonie

[Andromeda Stardust]

Each 6502 is imbedded with traces of a radio-isotope impyrity with a half life of approximately 30 years. Your particle decayed, killing the chip.

 

Seriously, I have no idea. I know I had a working Lynx I in 2007. I shelved it for five years, sitting in it's carry bag. In 2012 I plugged it back up. DOA. Finally replaced it in 2015.

[JamesD]

Entropy