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letzter Beitrag von Richard Hallas am

Pi1541 query

    I've just been reading about the Pi1541:


    Pi1541 project home page


    Superficially, at least, it looks and sounds like a good idea, with full 1541 drive emulation and support for all the common disk formats meaning that the large majority of software ought to work fine.


    Has anyone actually tried one of these with a MEGA65? Can it be expected to work properly?


    My personal experience with Commodore hardware is very limited; I started out on a PET 2001 and had brief use of a Plus/4 a few years later, but I mainly grew up on other platforms so I've little direct experience of the C64 and other 'mainstream' Commodores. So my questions would be:


    1. If I got one of these add-ons, would it be likely to work at all? (I've really no idea what an Epyx FastLoader cartridge does, but it appears to be an important component of this.)

    2. It also needs to plug into the serial port. Is that the same as the port labelled 'Disk Drive' on the MEGA65? (I think so, but am not 100% certain.)

    3. Would it be likely to work on both MEGA65/C65 and C64 personalities of the machine, or probably only in C64 mode? Would it do any *harm* in non-C64 mode?

    4. In the longer term, would it even be necessary at all on the MEGA65?


    Ideally, it would be nice to think that the MEGA65's own software would provide a nice and advanced file-browsing facility that supported all the disk and tape formats and allowed one's library of files to be stored conveniently in a hierarchical folder structure. Unfortunately, though, at present that simply isn't the case. Only D81 images are supported and they need to be unfragmented to work. Moreover, there seems to be no way to file them nicely in a folder structure: only a flat set of files at root level appears to be supported right now.


    I hope that native support for all common file formats and support for a nicely organised filing structure might arrive in due course in the MEGA65's supplied software, but I don't know that it will and it could take a long time. In the meantime, a device like the Pi1541 sounds pretty ideal for building and easily accessing a convenient software library.


    However, I've no prior experience of using this sort of thing on a Commodore machine, and in any case, a MEGA65 is sufficiently different that there may be hardware or software compatibility issues that I'm not aware of. I don't want to blow up my MEGA65!


    So, any advice would be received with gratitude and interest.


    NB The one obvious *physical* hardware problem I've noticed is the location of the cartridge port in relation to the serial/disk drive(?) port: on the C64 and other machines, the cartridge port is way over on the right of the machine (looking from the front). On the MEGA65, it's at the extreme left. Unfortunately, the Pi1541 is designed with a cable that comes out from the left of the cartridge and goes to the serial port, and on the MEGA65 this means that the cable will have to be folded awkwardly over the top of the cartridge. At least the serial port is right next to the cartridge port on the MEGA65, so a shortish cable (as supplied on the prebuilt versions on eBay) is likely to reach, but it'll be an ugly setup that obscures the display – unless someone produces a version specifically for the MEGA65, with the cable emerging from the other side of the cartridge.

    I would say, it should work, as it "speaks" the IEC protocol like 1541 and other "usual" drives, and MEGA65 also has an IEC port. So in long term, I see no difference between using Pi1541, SD2IEC or "real vintage IEC drive". However keep in mind, that currently AFAIK there are some issues with IEC on MEGA65 in general, but hopefully sooner or later those will be (maybe are? ...) fixed.

    Zitat von Richard Hallas

    1. If I got one of these add-ons, would it be likely to work at all? (I've really no idea what an Epyx FastLoader cartridge does, but it appears to be an important component of this.)

    I don't think the epyx fast loader currently works correctly (at least at the moment). But you don't really need it. It's just one of many ways making disc accesses faster (because of the horribly crippled serial protocol that the IEC bus uses; there's quite a history behind hit, but the bottom line is that the CPU is doing the handshake via software despite the presence of timer chips that could do the task 10 times faster).


    Zitat von Richard Hallas

    2. It also needs to plug into the serial port. Is that the same as the port labelled 'Disk Drive' on the MEGA65? (I think so, but am not 100% certain.)

    yep!


    Zitat von Richard Hallas

    3. Would it be likely to work on both MEGA65/C65 and C64 personalities of the machine, or probably only in C64 mode? Would it do any *harm* in non-C64 mode?

    It will work in both modes


    I have used both the 1581 and 1571 drives with my M65 dev kit, as well as a SDIEC drive... and I would say they all work intermittently, occasionally locking up the bus. But as far as I understand it, the IEC bus is still being worked on. In any case they work well enough to load some programs (although I wouldn't trust them with my life at this point...)


    Zitat von Richard Hallas

    4. In the longer term, would it even be necessary at all on the MEGA65?


    Well Paul plans to do a 1541 emulation for the M65 (still lots of free space in the FPGA), so in the longer term it wouldn't strictly be necessary... but until the emulation is there, it's a nice way loading d64 disc images ;)