1. Not old. Vintage. :)

65c02 CPU adapter board for Atari 8 Bits

Discussion in 'SIG: Atari 8-Bit Hardware' started by Vyper68, Jan 23, 2021.

  1. by Vyper68
    Vyper68

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  2. by Andy Barr
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    Hehe.

    Absolutely, Rich.

    He reminds me a lot of Jurgen Klopp, this guy(!) but he's very human, very honest and flags up the issues and how compatibility with the Freddie chip and other subtle (I think he referred to his 65XE as being "flaky"?) differences between the XE and XL series can result in these odd graphic issues etc.

    I'm sure this vid would be useful to folks undertaking similar adaptor board projects and running into... WTF? problems etc.

    Cheers, mate.
     
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  3. by Graham
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    Yep
    Jan's on my watch list. mind you he could have just checked a replacement Super Color Card for the 400/800 as lets you use either.
    There are adapters for a 65c816 as well..
     
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  4. by M.D.Baker
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    So are there any advantages to this besides a newer low-power consumption chip or in case the old 6502c (right?) become a rarity? I've got a few extra 6502c and 6502b chips on hand if ones in my machines die, and I'm not worried about saving a little power as even with all the upgrades in my two machines, the 31VA Atari PSU's I use still have amperage to spare.

    The only issue I had with lots of upgrades are PHI2 signal issues, at least with the 1200XL, haven't seen this problem with my 800 yet. But just installing newer, faster and lower power consumption 74LSXX IC's with newer 74HCXX (or other compatibles) as well as precision sockets and new capacitors have done the trick for me, plus the fact that now I no longer have an internal 256/512K Rambo and older dram chips and instead use the external Syscheck 2.0 XL with 512K sram AND an on-board PHI2 signal generator, the PHI2 signal issues have disappeared and allow me to use PBI compativel cartridges like MyIDE II and other PBI devices as the PHI2 signal from the Syscheck board helps them as well.

    I don't thing 6502c's are that hard or expensive to obtain yet either. Since there can be issues with this 65c02 board too, I really don't see the benefit, but please, enlighten me if there is something I am missing!

    Of course I have not watched the video yet, which I will do now...
     
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  5. by M.D.Baker
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    I'm at the part of the video where he's doing them Self Test, and has the flicker, and I want to scream at him that the flicker is NOT due to the adapter board, I've seen this myself on multiple occasions and it's been the graphic chips or MMU that had to be replace to get rid of the flicker! Now to continue and see if he figures it out, but he mentioned moving it to another machine, so...ok, so I guess in his case it was the 65C02 since the Sally stabalized the memory test screen...I may have forgotten, and had to replace CPU to stabilize graphic glitches like this too, before. I've worked on so many...

    Ok, watched the whole video, see that it's working in his (already restored) 800XL. I bet he replaced capacitors in it when he restored it too, since he said a friend's 130XE works fine with the board. New capacitors would make sure proper amounts of power are getting to everything and would probably help out the PHI2 signal as well, which can cause such issues.

    An interesting video, but before I started testing the machine, stock or with a board, I would have checked all the capacitors and make sure they are at least working properly, and at least replace those not within tolerances if not all capacitors (yes, I myself have been lazy enough on occasions to only replace what is "broken" even though it's best to be preemptive).
     
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  6. by M.D.Baker
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    Now that I think about it, with my first assertion of whether a lower power consumption CPU would really help out or not, it made me wonder if that board, with all the supporting IC's on it isn't negating that advantage anyway, newer 74 series IC's or not, and may, in fact, use more amps of power? I'd have to do the math by the specs, but I think my guess rings true.
     
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  7. by Graham
    Graham

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    Hi Matt
    Actually there's a big diffrence in overall power consumption, even when you include the additional Logic, think these are HCT devices as it has to go from TTL to CMOS levels which are a bit more piccy to voltage level. (CMOS harder to drive from TTL)
    I believe that some of the original optcodes that hand't been documented by MOS are still in the 6502C Sally chip I can't be sure they still exist in the 65c02 however there are documented additional opcodes in the CMOS CPU's
    It is possiable that some Atari software could use the original undocumented optcodes, but would not work on a non Sally chip computers, as not all 400/800's had Sally chips these programs wouldnt work on these varients either. EDIT : but the non SALLY also had the same optcodes so wrong on THIS Doh :(
    have a look here as just searched.
    https://wilsonminesco.com/NMOS-CMOSdif/

    EDIT: Checked Jan's github that Richie pointed to and uses HCT chips to buffer the the levels, but uses LS chips for glue logic. Also I'd put that CMOS harder to drive but it's TTL other way round :)
     
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  8. by M.D.Baker
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    An enlightening and interesting read, thanks Graham.
     
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  9. by Graham
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    Your Welcome, and I did read through it myself, the so called illegal opcodes don't exsist in the 65C02's but definatly have additional optcodes added, mainly in the area of addressing, I've copy and pasted for those that dont wish to trawl through the webpage I'd linked. EDIT no didnt work so you have an image instead..

    6502vs65C02.png
     
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  10. by Graham
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    I know Berdardo (The Byte Attic)
    has recreated an adapter for the 65C02 .. however note this circuit from 1989, on the text with this it mentioned it had been reverse engineered from the early 800's that used a standard 6502 prior to the re-engineered 6502C 'Sally'

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     

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  11. by M.D.Baker
    M.D.Baker

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    As the wheel turns...from lots of supporting IC's, to a re-engineered Sally and back to lot's of supporting IC's again, the usual viscous cycles man puts him self through in the name of advancement.

    And the wheels on the bus go round and round, round and round...next up, a re-engineered 65C02 from some modern programmable chip to get rid of all the extra IC's again that just plugs into the 6502C socket!:p
     
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