Re[2]: A parallel interface for PET, VIC-20 and C64/C128

From: Frank Kontros (
Date: 1999-08-04 14:12:50

Hello Marko,

Wednesday, 4 August 99, you wrote:

Marko> Yes, of course I'm interested.  Perhaps then I will finally have a disk
Marko> copier that does its job in a reasonable amount of time (such as 1-2
Marko> minutes).

My version copies one 1541 diskside under 25 sec.

Marko> What about using fuses on each line? :-)

Or ferrit rings at each line :-))

>> Marko> With careful design, you could make the software auto-detect on which
>> Marko> computer it is running. :-)
>> Hmmm. How? Eg. KERNAL patch. Make all routines in 3 or 4 versions?

Marko> Make the default load address $0401, because that is the start address of
Marko> PET BASIC programs.  Then assume that the load address is $xx01 and invoke
Marko> the machine language with a line of BASIC code:
Marko>  1999 SYS256*PEEK(44)+something
Marko> Then the machine language will detect its running address
Marko> (LDA#$60:STA$0100:JSR$0100:TSX:LDA$01xx,X and so on) and patch the
Marko> routines and/or the routine that installs them accordingly.  The hardware
Marko> can be detected by looking at some ROM locations or at some locations that
Marko> ought to have I/O chips.

That usable only for software's. But what about changing firmwares?

>> Don't know. Maybe you can source 74HCT74 from LPT port of PC too.

Marko> I wouldn't count on that.  There are so many different types of PC
Marko> parallel ports around.  It is true that this cable is only designed for
Marko> PS/2-style parallel ports, but having seen how many differences there are
Marko> between the "traditional" PC parallel port designs, I would rather do the
Marko> kludges on the Commodore side.

Well. But outputs are mostly at same place on any LPT port. If you use
bidirectional 8-bit lines, you have 4 extra lines for power.

Marko> So, is it safe to use the DIAG input as a power source, and does it have
Marko> other functions than activating the diagnostic routines?

I never had deals with PET models.

Best regards,

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