ACA500plus with MC68HC000FN20...?

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Don't Panic. Please wash hands.

    A hypothetical question: Did anyone ever try to run an ACA500plus with a FN20 part CPU? Those are 20MHz guaranteed from factory. My ACA500plus runs fine on 21MHz (stress tested with Elite Frontier and some demos), but crashes on 28MHz -- which is fine. I am wondering if replacing the CPU with a 20MHz part would result in more headroom for overclocking. Or are 20MHz CPUs just factory-selected regular parts that get unstable, too at 28 or 42 MHz. I do understand that the 10MHz parts are probably much more readily available so that's probably the reason for selling the ACA500plus with that part.

    The number after "FN" says less than the mask set. The fastest are E72N and G54B (both 0.8µm mask sets) and then come the 1.0µm mask sets, which were all calcelled in favour of the 0.8µm sets. As a result, C71T is a very rare mask set, actually missing from my collection.


    I believe the current ACA500plus all have J82M, which has actually replaced the E72N mask set, so it's unlikely that you can get anything faster. I don't have the actual mask set technology/die shrink info about J82M, but it's likely to be 0.8µm. I therefore would suggest to try a better power supply before soldering a new CPU and putting the card in danger.


    If your card has a CPU mask that I didn't list here, I'm happy to look it up.


    Jens

    As said this was more hypothetical and the mask set info was exactly what I was looking for. Yes, stronger PSU would also be something I would have considered. However I think I am also content with 14/21MHz. This is more my curiosity speaking.

    Quote from Jens

    The number after "FN" says less than the mask set. The fastest are E72N and G54B (both 0.8µm mask sets) and then come the 1.0µm mask sets, which were all calcelled in favour of the 0.8µm sets. As a result, C71T is a very rare mask set, actually missing from my collection.

    Do you mean this C71T...? :-D So if I instead had an E72N or G54B I might have higher chances of overclocking?


    Naturally, I don't look at each and every mask that is being shipped, but yes, that's the rare 1.0µm thing. And yes, masks E72N, G54B and J82M will have a higher success rate when overclocking.

    Quote from root42

    Yes, stronger PSU would also be something I would have considered.

    "strong" is not what you're looking for - it must be "better regulated". The whole trick is to regulate what actually arrives in the computer, rather than regulating what's at the output of the PSU. Those Elektroware/A-Power/Centurion/Keelog things all use some PSU chassis, even add a display of sorts in some models, only to fail on voltage drop on the cable. This is just *so* wrong, and people don't get why their computers are unstable.


    Those "aftermarket" or "modern" PSUs are failing to meet all three of the three key specifications that Commodore has put out.


    I have been tempted to start lawsuits against those companies a number of times, but held back in order not to stir up the mood too much. It's enough for me that customers of the CA-PSU are reporting success on all fronts. Our PSU FAQ has all the technical details.


    Jens

    • New

    Good evening,

    I've just bought an aca500+ for a Rev6 A500, and I'm not able to go past 21mhz too. Cpu is a MC68HC000-10.

    Do you think that maybe it could be because of my PSU, a heavy one only rated 2.5 amps ? I haven't recapped it yet, will do that soon.

    Or because of the mask set, this is what we can only expect ?

    Thank you for this great product.

    • New

    I recently added the CA-PSU Power supply. I also have the FN10 CPU on my ACA500. Even with the CA-PSU, I am unable to get more than 21 MHz. However, the 1221lc I have attached to it will happily run at 40 MHz ( 44 according to Sysinfo ) with the CA-PSU. It would not with my stock Amiga power supply.

    • New

    Thanks for your reply. This is what i thought, so no need for wasting cash to buy a better psu as i don't need a >68000 cpu.

    Nevertheless, I would like to source a better 68hc000 and maybe try the swap. I'll see.

    I don't know if on the aca500+, its power supply is 3.3V.

    Maybe there is room in the firmware for adjusting the voltage a bit to the up ?

    • New
    Quote from Crossmanbx

    I don't know if on the aca500+, its power supply is 3.3V.

    Maybe there is room in the firmware for adjusting the voltage a bit to the up ?

    The CPU voltage on the ACA500plus is always 5V. Only the main logic and RAM is in the 3.3V domain. So any CPU you want to use in there must be able to run at 5V.


    Jens

    • New

    This is the current batch - we're building ACA500plus with whatever CPUs we can get. The current batch is "yet another chip shortage edition" - I'd have to look up what version number the board is, but it's the first time ever that we've used 68HC000 CPUs. Previously, it was 68EC000 and 68SEC000. The version number is on the solder side, near the 86-pin connector, should be V7-point-something.


    Jens