Re: BASIC for the CBM-II/8088

From: Bill Degnan <>
Date: Fri, 20 Jul 2018 09:22:04 -0400
Message-ID: <>
I have a P500 I converted to NTSC, happy to volunteer it for testing,
please advise.  Assuming I don't have to ship and that I can perform the
tests locally.

On Fri, Jul 20, 2018 at 7:43 AM Michał Pleban <> wrote:

> Mia Magnusson wrote:
> > Not sure which versions of V20 that's easy to source today.
> I bought some 20 MHz ones on Ebay a few months ago (and they work in the
> 8088 card like a charm ;-))
> > I think somewhere around DOS 3.x support for network started to appear.
> > I assume it would be a lot of work, but it would be kind of nice to
> > install the CBM Kernal API as a file system handler to DOS.
> Yes, DOS 3 introduces a network redirector interface. I have never
> looked at this interface but in theory it could work. However, I have no
> idea how much memory it would take on the 6509 side where space is
> already very tight.
> > (Not sure how the 8088 card, with either your or the original BIOS,
> > handles character devices but I assume it would be trivial to add
> > support for printers and the rare IEEE-488 modem and IEEE-488<->rs232
> > converter boxes).
> It is indeed quite easy. The original card software already had some
> rudimentary support for IEEE printers, which would unfortunately not
> work in MS-DOS however, because the 8088 code part is buggy, hangs the
> processor due to stack mismanagement and even tries to call INT 17 (!!).
> The support of the IEEE modem was also present but unused by MS-DOS; I
> removed it to save space.
> > As the P500 is rare itself, but as it afaik uses non-rare parts (except
> > for the triports and the CPU) I assume there isn't that much risk of
> > destroying expensive part by trying. Maybe we can convince someone here
> > on the list who has a P500? :)
> My P500 is in storage. I can go fetch it, but first I would like to
> finish the video memory emulation.
> > Yeah, I know. My idea was that the conversion might take about as much
> > longer time than a pure copy as the 8088 is faster than the 6509,
> > making them process each byte at about the same speed. It would take
> > some machine code programming with cycle counting to be able to
> > transfer a bunch of chars without handshake, but as it can be done
> > between a 1541 and a C64 it should be possible between the 8088 and the
> > 6509 on a B :)
> You cannot transfer data without synchronization, because the 8088
> execution time is nondeterministic - it can be stopped by the mainboard
> to refresh the DRAM at undetermined moments in time. So no matter what
> you do, you cannot write cycle-exact code for the 8088. That's why I
> wanted to synchronize the CPUs with the SO pin.
> What I ultimately want to do is to make the 8088 read a byte and convert
> it, then issue it via an IO port to the 6509 which will place it in the
> video memory, while the 8088 is already busy fetching another one.
> But it is a nontrivial task, so my first version will have the 6509
> simply refresh the screen once a second as a proof of concept.
> Regards,
> Michau.
Received on 2018-07-20 16:00:27

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