Date   : Sun, 17 Jul 2005 20:53:24 +0200
From   : John Kortink <kortink@...>
Subject: Re: floppy discs

On Sun, 17 Jul 2005 18:28:30 +0100, Sprow wrote:

>In article <4bthd19hl0onmlg8rj2l5s4vdr19di1p6g@...>,
>   John Kortink <kortink@...> wrote:
>
>[snip]
>
>> >But aren't those just used by emulators?  You
>> >can't use them directly with a real Spectrum.
>>
>> Not yet probably. However, for the BBC : I'm tinkering
>> with the idea of supporting playback of UEF files via
>> GoMMC. Although this may need a few slight adjustments
>> to the OS ROM, loading a 'tape' via GoMMC may eventually
>> be indistinguishable from the real, cumbersome thing
>> with cassette tapes.
>
>Why not make GoMMC respond to service call 13 and 14 and
>make it appear as a tape filing system image in ROM? No
>patching of the OS required.

Because a lot of games have a habit of liberally
peppering their code with things like *TAPE, *FX140
and *FX143,12,3 and/or their OS_Byte equivalents.
It better actually be the tape filing system, or
many games won't work without fixing them, and
being able to avoid that is the whole point of
using tape based games in the first place (else
get the disc version or the to-disc version).

Doing it all via the ROM FS calls is the first
thing that crossed my mind, but it just doesn't
provide enough compatibility.

>Since it doesn't appear to check whether it has read
>more than 16k from any one ROM, instead being prompted
>by the end of ROM maker (+), you could just funnel the
>data from the MMC card through the GoMMC ROM, into the
>OS.

Of course. Neither the tape filing system nor the
ROM filing system really care.

The way it all works now (because it already does,
see previous message) is (because the tape and ROM
filing system use largely the same code, with a few
switches here and there) that the OS is changed to
do the ROM FS byte-get service call 14 at four
strategic places, and GoMMC catches that. Works
a treat.

>Essentially, GoMMC would become a carousel of tape
>images in UEF format but not occupy any more ROM
>sockets.

But a patched OS obviously doesn't occupy an extra
ROM socket. It just loses the tape filing system,
currently. The ROM filing system still works, since
GoMMC can distinguish between real and tape-based
(hence patched) service calls.

I'll tinker some more and do a first release soon-ish.
Almost all of the UEF tapes from Stairway to Hell seem
to work fine (including nasty ones like Elite and The
Hobbit, Firetrack etc.).


John Kortink

-- 

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