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| Finding replacement 6502 for AppleII+ |
Posted by: LittleJackal on 2016-11-16 18:23:31
Was just gifted an AppleII+, unfortunately it's missing the CPU for unknown reasons. I'm hoping it's not trash and I'm willing to put in a few bucks to experiment.
Is there any guide on picking a 6502 replacement for an AppleII+? I picked up a pair of R65C02P4 processors from eBay because they were particularly cheap but I neglected to check whether they'd be suitable drop-ins. Mouser has the WDC W65C02S6TPG-14 for $10 a pop but shipping to Canada was $20 so I opted not to go with that. Not sure I made a good choice.
Can I expect my R65C02P4 to work fairly well, or should I be planning on another purchase?
Thanks!
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Posted by: Carboy7 on 2016-11-16 19:52:03
Maybe the 6502 was pinched to be sold...
I'm not sure where you can get replacements, other then evilBay.
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Posted by: Gorgonops on 2016-11-16 22:40:00
I don't know what they'll charge to ship to you but last time I checked Anchor Electronics in Santa Clara had plain old non-CMOS 6502s for about $4 each.
http://anchor-electronics.com
Edit: $4.95 on their current price list. They're Rockwell 6502Bs but one worked fine for me in a Commodore PET so I'm sure an Apple II won't have any problems.
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Posted by: Gorgonops on 2016-11-16 22:49:36
.. as for the 65C02s you bought... you might have problems. They're (mostly) elecrically compatible but there is some software for the II and II+ that depends on "undocumented instructions" that were replaced with NOPs on the CMOS versions. (This same software breaks on Apple IIcs and IIes for that reason.)
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Posted by: LittleJackal on 2016-11-18 09:26:13
Great, thanks so much for the info. I'll try to hunt for the real deal. In the meantime I'll at least check to see how I stand with the ones I bought, but it sounds like I can't do much damage popping them in as a temporary measure.
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Posted by: Gorgonops on 2016-11-18 10:21:32
I did some digging and it sounds like you should be fine from a "it won't damage anything" standpoint, but it might not work. Apparently some people have tried swapping in 65C02s intentionally to get some C-dependent software running on Plus's and they've run into issues they think are memory timing related. (Here's a thread. Apparently some work, some don't, and it may depend on the exact mix of ICs in your particular II. No offense to the almighty Woz but Apple II is frankly a pretty skanky design when it comes to sticking to specs.)
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Posted by: khannonnd on 2016-11-18 12:16:26
Did the 6502B just have a faster clock speed from the original 6502?
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Posted by: Gorgonops on 2016-11-18 12:48:22
Yes. It was typical back in the day for CPU manufacturers to add letter suffixes to their chips to indicate higher speed versions. In the 6502's case the standard no-letter version is 1mhz, a 6502A is rated for 2Mhz, and a 6502B is good for three.
(If you're looking at Z-80s the no-letter, A, and B ratings correspond with 2.5mhz, 4mhz, and 6mhz respectively, so the letters themselves don't mean anything specific. Oddly enough the next step up with Z-80s is the Z-80H, while some second-sources made 4mhz 6502s with a C suffix... not to be confused with a C in the middle, which means CMOS process and additional instructions.)
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Posted by: Gorgonops on 2016-11-18 16:28:28
I'm hoping it's not trash Just BTW, if it's broken beyond the missing CPU and you end up feeling like you want to trash it, well... I have no idea what cross-border shipping would cost, but before you throw it out I might be interested in some parts from it.
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Posted by: LittleJackal on 2016-11-19 12:36:16
Sure, I'll let you know if it turns out to be a bust.
Thanks for the advice.
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Posted by: falen5 on 2017-01-04 10:09:11
dont know if this is of any use for people in america with shipping - but i just ordered 2 of these - shipping was 1.20 euro to ireland
https://www.aliexpress.com/item/1PCS-UM6502-8-BIT-Microprocessor-UMC-UM6502-6502-INTERGRATED-CIRCUIT/32697415475.html?spm=2114.30010308.3.1.422mC6&ws_ab_test=searchweb0_0,searchweb201602_3_10065_10068_10000009_10084_10083_10080_10082_10081_10060_10062_10056_503_10055_10037_10054_10033_10059_10032_10099_501_10078_10079_10077_426_10103_10073_10102_10096_10052_10053_10107_10050_10106_10051-10050_10033_10037_10077,searchweb201603_3,afswitch_5_afChannel&btsid=fe9ce0aa-eb50-470e-ae11-b76fb299a421
Someone tell me that these will work in an Apple ][ !!!!
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Posted by: Gorgonops on 2017-01-04 10:29:31
I always have vague worries about the authenticity of ICs from AliExpress, but if it is what it says it is, a UMC UM6502, then it's a second-source copy of the NMOS version of the original 6502 and therefore should be just fine.
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Posted by: falen5 on 2017-01-04 16:27:24
Thanks Gorgonops - will report back when i get them if they work or not
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