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. Bill On Fri, Jul 20, 2018 at 7:43 AM Michał Pleban <firstname.lastname@example.org> 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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