Okay, fair enough. I didn't explain why I suggested we consider testing one-minute Resets -- even though the reported spec is 50-100 ms.

I once witnessed a malfunction where a 65C22 had 8 of its peripheral lines shorted. The chip got hot enough to burn my finger... and yet it worked fine after the short was removed and everything cooled down. Admittedly that's not an exact parallel to an NMOS '02, but it does lend support to my view that, in regard to heat, these chips are not easy to kill. (Heck, they bake 'em in ovens during manufacture, don't forget!) So, the next question is: how long does it take for a chip to get that hot? Even in the rather severe malfunction I observed, the power dissipated would only be a few watts. And, the 40-pin plastic DIP package and its socket have significant thermal mass as well as some heat-sinking ability. So: although it's only a "guesstimate," I find it unlikely that the chip could achieve truly destructive temperatures in anything less than several seconds. We can bracket that amount widely: on one side with our cautious engineer in the 70's saying 50-100 ms, seeking to avoid damage; and, on the other side, with you and Ed and our other 6502.org experimenters, who ought to tread harshly in attempting to confirm that damage can be done! That latter point is what led me to suggest one minute.

On a different tack, it occurs to me that the 50-100 ms figure may be quoted on the low side not for fear of toasting the cpu but simply in order to minimize the burden on the 5 volt power supply, which would be in its power-up sequence during the time RST is asserted. Ie, the power supply might fail to wake up properly.

-- Jeff

For our present experiments, I think holding a finger to the CPU to see if it gets hot should be enough?


Sorry about that - I seem to have left stubs! Letting me know on this forum is one way, or by means of a PM, or a note on a Talk page, as you have done. I will update the User Guide, but as a quick guide:

- interactively, you can click on the memory map and change the content of each location
- in the URL, you can use a= and d= to patch any addresses with data. So ...&a=400&d=eaea&... would put a couple of NOPs at $0400. Use the same technique if you wish to adjust the vectors at the top of memory. You can load quite long programs this way (in several sections, usually)

That would be great!

Cheers
Ed

You could use a IR digital thermometer gun I use one all the time to check for board hot spots... And it saves your finger tips....

_________________
When falling from a high place, You might as well try to fly

Hmmm... good idea. But the old manual method works, too. Which reminds me of some amusing terminology I recall hearing somewere. Informally speaking, the sacrificial fingertip was referred to as a "digital wattmeter!"

Yes, that'd be the approach I would take. Touch the center of the chip and continue doing so. Then hit RESET for at least 20 or 30 seconds (or until you notice heat). If there's a serious excess of dissipation then you're apt to feel it in the first 5 seconds, but a less severe case will take much longer to become perceptible.

-- Jeff

That's about the same as when my boss called me in his office and said a customer reported I was beating on the video poker games in anger,, And asked me what the He!! I was doing... I told him it was a high impact circuit integrity test..

_________________
When falling from a high place, You might as well try to fly

And I suppose bridging two live terminals with one's finger constitutes a digital voltmeter.

Silly me. All these years I've just been calling it a "thump!" But your term sounds much more schooled and impressive!


Yes, exactly so! Just be aware of proper use of the Range setting when using these precision instruments:

• with the digital wattmeter, you lick your finger before measuring very high temperatures. Conversely,
• with the digital voltmeter, only lick your finger if the voltage you're measuring is low.

cheers,
Jeff

I digress slightly, But years ago when they had the New York power blackout.. The Tech that found the problem was asked what he charged the city for fixing the problem, Which had been a relay with welded contacts... His answer was " 1$ for tapping, And a $1000 for knowing where to tap..

_________________
When falling from a high place, You might as well try to fly

I work in the protective relaying for high-voltage power transmission. I shared this with the guys and they all laughed. This is very true - our problems are usually easy to fix, you just have to know where to look!

Glad you got a good laugh from it ...

_________________
When falling from a high place, You might as well try to fly

Sorry for digging down to 2011, but I think it's worth sharing. Some first-hand information on the subject:
https://www.youtube.com/watch?v=DXRvCnmLj7A&t=3000
It seems that the original MOS Technology 6502 had a 200Ω "resistor" from Vcc to GND built into the CPU. Doesn't seem like a lot, however it seems like there were more things making them overheat, fixed in early 1990s.

Interesting! So that would be 25mA, I think, or 125mW. That's quite a chunk compared to the 700mW total (on a random Synertek datasheet.) Although we hear from Bil Herd there that this was fixed by the Commodore were making their later devices, we don't know if the anecdote might be from the really early revisions - it was revision D that was generally used, fixing the ROR bug, about a year after introduction.