6520 alternatives

[circuit]

I've read that W65C21S , 6821 may be usable as substitutes for the venerable 6520

Can anyone confirm from experience if this is true? Particularly in PET systems

 

[KC9UDX]

Yes. Particularly.

 

[circuit]

Yes. Particularly.

That is particularly good news - thanks :D I shall order some.

 

[deathshadow]

I've used MC6821's to bring dead joystick ports in Atari 800's back to life -- those shipped with a MCS6520. I would avoid the older MC6820 as it's not as "up to spec" electrically as the 6821 or the 6520. In theory on something like a PET the differences shouldn't rear their ugly head, but when there's newer revisions designed to be stable at higher speeds, I've always found it better to err on the side of caution.

"Mr. Scott" engineering. Figure out how much you NEED, then double it for a safety margin.

 

[KC9UDX]

Early PETs came with 6820s.

 

[deathshadow]

Early PETs came with 6820s.

Well... that's different then, nevermind.

At that pont pretty much any of the different versions would work properly.

 

[JonB]

Good news for me too. I seem to be frying these on a regular basis for some inexplicable reason.

 

[channelmaniac]

I have 100 of the 6520 ICs in stock.

6520, 6820, 6821, and in most cases the 6822 can be swapped in and out of circuits with ease. Sometimes you need to have pull up resistors on the I/O ports of the 6822, depending on the circuit.

If you have some spare cash, pick up a tester from these folks: http://www.neoloch.com/

It will test SRAMs, PIAs, and now 4116 DRAMs. I still need to order that DRAM blade for my tester. This thing really kicks butt.