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Old 6502 From My Parts Drawer

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saundby

Experienced Member
Joined
Jul 21, 2009
Messages
306
Location
The Villages, FL, USA
I've got a rough old 6502 from my parts drawer that I pulled out last night. I hadn't realized it was quite so old. I've been picking around it for decades, it got its legs bent under but I believe it to be functional (or at least it was moments before the legs got bent.) I'm carefully pulling the legs back into shape with the idea of sticking it in a free-run circuit to get a first look at what sort of shape it's in other than the obvious cosmetic damage.

Is this old enough to have the ROR bug?
Web_MCS6502.jpg
 
Test it and find out. You either have one of the last with the bug or one of the first without it. Made May 1976; bug supposedly fixed by June 1976.
 
Given the potential value of the chip, I’d spend some time cleaning the ceramic. I did this with some success on an INS8080 a few years ago, I think that I used Ajax and a toothbrush after it was socketed. Being ceramic, I didn’t worry about moisture but I would stay away from the chip on that chip :)
 
Do not clean the chip!
It is worth more with an authentic patina.
You could loose important parts of the print as well.

It can fetch up to $1000 and usually goes for >$300.
The 1976 6502 is very rare and sought after by Apple 1 owners.

-jonas
 
saundby said:
Thanks, I won't clean it. Should I straighten the pins and test it?
Click to expand...

I would not try to bend the pins too much.

The CPU is already damaged and too much force could break off a pin or chip the ceramic more.
You could try to test it using a ZIF Socket and bend the pins just enough to get a connection.

It most likely is still functional since these CPUs are normally very robust.
But even if it does not work, it will still be worth good money to a collector.
Often collectors are interested more in 'looks' and original components than in functionality.

-Jonas
 
stynx said:
Do not clean the chip!
It is worth more with an authentic patina.
You could loose important parts of the print as well.

It can fetch up to $1000 and usually goes for >$300.
The 1976 6502 is very rare and sought after by Apple 1 owners.

-jonas
Click to expand...

Perhaps to some, but dirt and a pen mark, easily recreated, does not strike me as “patina”.
Of course, the lid and any factory marks on the bottom are off-limits for cleaning.
 
There is another reason to not clean it. The legs are gold plated. There will be tiny voids under the gold that whatever cleaning agent you use can get under the gold. Once there it is almost impossible to get the last little bit of it out from there. Over time electrolysis will rot the cores of the legs. Then it will be bad. I've been working on trying to recover data from some 1702As. Some of the leads are hanging on by the gold only. I don't know what the history was but I'm sure it was something that they shouldn't have been exposed to.
In any case, the ceramic is chipped. I'd avoid anything that might make it worse, if you plan on selling it.
Dwight
 
saundby said:
I've got a rough old 6502 from my parts drawer that I pulled out last night. I hadn't realized it was quite so old. I've been picking around it for decades, it got its legs bent under but I believe it to be functional (or at least it was moments before the legs got bent.) I'm carefully pulling the legs back into shape with the idea of sticking it in a free-run circuit to get a first look at what sort of shape it's in other than the obvious cosmetic damage.

Is this old enough to have the ROR bug?
View attachment 49660
Click to expand...

I made my Apple I clone a few years ago and since then I’ve been looking for that white MOS 6502 chip. Are you selling it? :)
 
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