Those are both plausible theories. But maybe the upper chips (and their plastic packages) have simply been spun 180 degrees, and the pinout is such that the spin results in no effective change for most of the pins. But there's a Chip Select pin that ends up in parallel with a no-connect, and a no ...

Just a normal DIMM, 1GB DDR333 ECC REG
http://forum.6502.org/images/migrated/076646-000.jpg

But wait!

http://forum.6502.org/images/migrated/076646-001.jpg

Probably designed to be mounted this way, all pins are connected between two chips, nothing is routed around. 36 memory chips, 40 chips ...

I believe those sockets have Rifa caps inside (known for popping and releasing magic smoke). Experienced similar thing twice: first time with ancient CDD-521 CD burner, then with an old oscilloscope. After the smoke is gone the thing is working, except for capacitors having 0nF now. Fun

This chip might be NMOS 6502, rebranded by Chinese "businesmen" as 65C02. Try running it at higher clock speed (above 100kHz).
I ordered 5 chips a few years ago, got 3 NMOS and 2 CMOS, rebranded as Rockwell 65C02. link: http://forum.6502.org/viewtopic.php?f=4&t=4593
The only eBay seller I found ...

Roger, ordered BAT85 diodes, but I'll consider some faster logic anyway. I don't have HC/AC11 in my collection, will order some anyway, along with other stuff.
Using some programmable logic could make identifying IRQ sources simpler (reading one register), not to mention guaranteed delays. Just a ...

Added some diodes to IRQ lines. I hope that 1N4148 will be good enough, if not, there are still some JFETs around

Markings:
W65C22S6TPG-14
SA1309A
A4V338.1
Taiwan

How do you know they are genuine WDC parts? I bought some, W65C22 is consuming less power than NMOS 6522, outputs are stiffer too. This guy is selling PLCC versions of all chips, most China sellers have only DIPs. It might not be definitive clue, but leads are mat, it looks like tin was deposited ...

There are some local trusted sellers here too. One even has original AMD 80386 chips from 1993, at the original retail price (they seem to ignore inflation) :D Got most chips for my project from his shop. Another is also liquidator, he sells a lot of Z80-related stuff, and quite a lot of 1970s to ...

While I was getting materials for my computer, I stumbled upon some 4MHz Rockwell 65C02 chips, allegedly produced in 2014. Hmm. The same seller had NMOS Rockwell 6522 chips, also produced in 2014. Do I smell a fish? Or maybe I am wrong?

I ordered some: "5pcs" of R65C02P4. Here is what I got (they ...

It works! After some time, and with second attempt. First one was classical "I want everything there", which failed.
http://forum.6502.org/images/migrated/054028-000.jpg
http://forum.6502.org/images/migrated/054028-001.jpg
http://forum.6502.org/images/migrated/054028-002.jpg
http://forum.6502 ...

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 ...

Hello,
My name is Hubert, and I like to do things considered by many as impossible. My adventure with 6502 started in early 1990s, when I got Atari 600XL (second hand). Then I got another Atari (800XE), Commodore 128D(CR) -- real programming started here. I remember someone telling me that coding in ...