From: Marko Mäkelä (msmakela_at_gmail.com)
Date: 2008-03-06 15:01:59
On Thu, Mar 06, 2008 at 11:31:26AM +0100, MagerValp wrote:
> >>>>> "MM" == Marko Mäkelä <msmakela@gmail.com> writes:
>
> MM> It could keep serving the loaders in a round-robin fashion (e.g.,
> MM> C64, VIC-20, C16, C128, PET) until the computer gives a special
> MM> signal that indicates that the loader has started.
>
> Wouldn't it be possible to write an autostarting loader that works on
> all platforms? Or is it not possible to load to the default basic
> address (04/08/10/1c01) from tape? I haven't used tapes for 20 years
> now, so I can't remember...
That wouldn't work on the B series, whose BASIC programs start at $0003
or so. But the B series firmware lacks tape support anyway. (There is
a tape connector, and I've read rumors of a tape-support cartridge.)
Then the loader would have to be significantly larger than c2nload's
minimal-sized loader that is 192+2 bytes, and it couldn't be
auto-starting. The c2nload loader resides in the tape header (which
normally contains only the file name), and the 2-byte payload overwrites
the "PRINT" vector so that the computer will jump to the tape header
as soon as it tries to display the "READY" prompt.
It should be possible to implement a cross-platform loader in a hybrid
of BASIC and machine language. But it wouldn't be auto-starting; you'd
have to RUN it.
The c2nload "PET" loader is a start. It auto-detects the BASIC version
and the tape port. The loaders "8032-1" and "8032-2" auto-start on the
PET 8032, assuming tape #1 or #2. (Older PETs do not have a PRINT
vector in RAM.)
Marko
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