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Re: Can anyone help me with Apple CP/M
In article <394FEF16.E7D0D8E6@pacific.net.au>,
Matt Jenkins <mdj@pacific.net.au> wrote:
> Paul Schlyter wrote:
>
>> You could reuse the nibble and sector buffers of the "CP/M RWTS" for
>> the standard 5.5" drives though: I'll find out where they reside.
>> Since CP/M logically uses 128-byte sectors, one had to buffer the
>> standard Apple II 256-bytes sectors too.
>
> Well, yes, but that's 256 bytes, not 512. I suppose the UniDisk could be
> hacked to do 256k sectoring, but I'd rather be compatible with the
> ProDOS system so the disks can be duplicated by standard utilities.
the byte buffer is 256 bytes, yes. In addition, you have the nibble
buffer which is 256*8/6 bytes.
>>> plus room to fit modified blocking routines for CP/M sector translation,
>>> so unfortunately it seems I either replace the existing disk framework
>>> with 3.5" only support (which would be okay except for the fact it'd
>>> make getting data on/off the 3.5" disks impossible)
>>
>> Not impossible - just harder. Use a null modem cable, a PC, and
>> Kermit, XModem or YModem on both ends... :-)
>
> Yeah - I'm in the process of setting this up anyway.
>> So if you don't intend to ever boot CP/M from your Unidisk, I see no
>> reason why you cannot configure them for 0 system tracks, and thus get
>> a little more disk space for your files.
>
> That's an interesting one. Does the boot drive have to become logical
> drive A: in CP/M ? It'd really complicate issues if this happened.
AFAIK, yes.
>> I think they re-wrote CP/M itself, to make it runnable in that bank
>> switched environment. To applications, the TPA was still un-banked.
>
> Ah, probably just shunted their BIOS into the 2nd bank so than the BDOS
> could load higher. I guess in that sense it's not really a 60k system,
> just a neater version of the 56k system, since the linear memory
> available to the Z80 doesn't really change.
The TPA grew larger though.
--
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Paul Schlyter, Swedish Amateur Astronomer's Society (SAAF)
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