forum.defence-force.org

actually, follow-up query on the Jasmin: if you can select arbitrarily many then how do you deselect drives? Drive 0 -> 0x3FC, Drive 1->0x3FD, Drive 2->0x3FE, Drive 3->0x3FF To select a drive write 1 to the corresponding address and 0 to deselect. Cool, thanks! I'm going to hold back on iss's sugge...

Most importantly: the BD-DOS spin-down issue is 'fixed' (in the sense: I've taken a different guess at the sort of RDY it's expecting from the drive) in a new release . Otherwise: Sync 60Hz is out of sync because it is genuinely out of sync. The simulated Oric produces a real 1d video signal with ap...

Some more quick observations on this, relevant to yesterday's botched release: The boot ROM performs: seek to 0, read boot sector, check for errors (including drive not ready). Somewhere between then and the command prompt, the logic changes to: (i) issue a force interrupt and check for drive not re...

It's late in the day, so I'll be quick: I've uploaded a new release that takes a shot at Byte Drive 500 emulation. EDIT: it appears there’s a dangling bug with drive spin-up on the Byte Drive; it’ll happen the first time but not subsequently. Either issue all of your DOS commands really quickly, bef...

Further notes, probably the final for today: The boot sector accesses $0311 and $0317 only. It has a check for BASIC 1.0 (at 04a5–04aa in the disassembly above). Therefore either $0311 or $0317 must disable the disk ROM, and the other must do something else. It seems safe to respond to either and ig...

Fabrice's notes are a little vague on what accesses other than to the WD do (at least when read through automated translation), so I am brute-forcing the problem, with slightly weird results. Per Fabrice, the accesses other than to the WD are probably to Apple/Pravetz-esque soft switches. I seemed t...

Fantastic, amazing! I'm sure we can figure it out from the ROM and a disk image. Given that the intention of the Byte Disk was to be the disk drive for every platform, showing only the relevant files on each, it might also be fun to try to figure out the on-disk format. There's possibly non-Oric ver...

Probably the actual easiest thing for answering these sort of questions for myself would be to learn French.

Pulling on that thread there seem to be articles in both CEO-Mag #154 and 155. So a quick subscription to that is probably the best plan.

BD-DOS, for the Byte Drive 500, is mentioned on the Wikipedia Oric page and reported on non-Oric forums as though it were primarily an Oric device. It appears in photographic form in CEO-Mag #272.

Has anyone preserved BD-DOS and/or any technical information for potential emulation?

I've just discovered possibly the most egregious of false sync situations: On track 41, the ID mark for any normally-written floppy will be [sync] A1 * 3, FB 29. The final nine bits of that sequence are 000101001, which MFM encodes to: 01 01 00 10 00 10 01 00 1x, i.e. the C2 sync followed by 00 1x. ...

... Jasmin's independent clock should cause a race condition on the data request bit ... Yes, there is such race condition and even more - what you read from status/data registers depends on alignment of some addresses :shock: . I'm preparing to publish lot of info which I've collected recently... ...

It'd be interesting to know what the problem was if anybody can fill in that detail? I couldn't think of a reason that the Jasmin's independent clock should cause a race condition on the data request bit given that it's reset only when you actually read data, not just by reading the status, and ditt...

Regarding text mode, it's only a 8x speedup on the rasterization, I'm not sure that such a huge improvement, considering how difficult it is to do dynamic allocation of characters, Like all games, I was imagining a heavily-simplified allocator: If you had the first 120 characters to allocate, set a...

Thanks, @ThomH ! Perfectly timed release - just what I need at the moment :). That’s lucky! I saw elsewhere that there were some floppy images that work under emulation but not on real hardware; in case it’s relevant, I’ve implemented all Jasmin-specific registers as write-only, with the FDC mirror...

Well, what I wanted to do was to extend the system to use span buffers and delta screen updates, but I never quite managed to find an efficient way of doing that. ... I tried the same thing over in Z80 world, maintaining an ordered span buffer (which makes the differential draw trivial) but my reas...