Does anything use the Microdisc interrupt?

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ThomH
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Does anything use the Microdisc interrupt?

Post by ThomH » Tue Oct 29, 2019 4:03 am

I have the strong feeling that none of the Oric's operating systems use its hardware interrupt, since it's not all that useful — it primarily marks the end of an FDC instruction, but since the Oric doesn't use DMA for disk transfers there's never really much ambiguity. I guess it might be useful for longer seeks, if there were anything else the OS could be doing while the drive is seeking.

Is that a fair assessment?

Naturally I have an ulterior motive for asking what is otherwise a dry piece of trivia: I discovered earlier this evening that my emulator doesn't reliably propagate the FDC interrupt signal, and it'd be interesting to have a non-synthetic test.
Last edited by ThomH on Wed Oct 30, 2019 4:18 am, edited 1 time in total.

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Dbug
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Re: Does anything use the Microdrive interrupt?

Post by Dbug » Tue Oct 29, 2019 8:32 am

Based on http://oric.free.fr/programming.html it seems that some OS does that:
Jasmin's electronics also features buffers for side/drive selecting, and memory signals, but the DRQ line is connected to the system IRQ line so it allows for interrupt-driven transfers (however, two consecutives bytes are separated by 31.25 micro-seconds, so the interrupt routine has to be fast ! As an example, FT-DOS uses a dedicated interrupt routine, and does not even have time to save registers: the interrupt routine lasts 28 cycles)
André Chéramy and Fabrice Frances could probably give you better answers regarding the inner working of all things FDC related.

ThomH
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Re: Does anything use the Microdisc interrupt?

Post by ThomH » Wed Oct 30, 2019 3:35 am

That's the Jasmin, which is the only one the emulator doesn't currently cover — it's got only the Microdisc and Pravetz disk interfaces implemented. Though, honestly, I should probably throw the Jasmin in as clearly FT-DOS is Jasmin-specific and therefore there is currently Oric software the emulator can't run.

EDIT: oh, I've just spotted the mental slip in the original title. Definitely Microdisc, not, ugh, Microdrive.

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