Date   : Fri, 13 Mar 2009 08:50:30 +0000
From   : philb@... (Phil Blundell)
Subject: BBC Micro CD-ROM?

On Fri, 2009-03-13 at 07:54 +0000, Rob wrote:
> I would think it's fine for the driver; a bigger problem might be
> memory to store the larger block sizes.

Assuming it's going to be a read-only filesystem, I think it ought to be
possible to manage with only a fractional-block buffer (say 256 bytes)
in main memory.  As far as I know there's no reason you can't stall the
ATA(PI) interface indefinitely in the middle of a block transfer, so you
could issue a read command, suck out the first 256 bytes, do some
processing, then come back later and suck out the next 256 bytes and so
on.

Obviously random access would be a bit slow that way, but for the
(presumably more common) case of mostly-sequential access within a
sector I imagine it would work OK.

Not that I can immediately think of much CD-ROM content that would be
useful to access on a beeb, but still... :-}

p.