Date   : Wed, 07 Jan 1998 18:36:41 +0000
From   : Tom Seddon <tom@...>
Subject: Filing System Speed considerations

After a *long* break I have resumed work on my BBC emulator with a
vengeance. I am currently writing myself a new and promising-looking
filing system, which is able to use directly the standard (archive)
format files. It also has proper random-access support and all the other
things the old version lacked.

Anyway, my question is a filing-system-related one. I've written the new
filing system *extremely* defensively, with checks and things all over
the place, and I don't keep files open any longer than is necessary
(_open and _close calls everywhere!). The upshot is that the filing
system is *unbearably* slow without Smartdrive, but about manageable
with, or when running under Windows '95. Does anybody who is interetsed
in my emulator have a *major* problem with this? I don't intend to do a
great deal about it for this release but I might program with the
possibility of future speed improvements in mind, which is something
I've completely ignored so far in favour of ease of programming.

Oh, and when I have finished the filing system it will be available to
anybody who wants it. It consists of a 6502 ROM, which handles the BEeb
side of things, and three source files: one contains the filing system,
one contains functions to emulate OSARGS etc, and one contains the
handler for a new instruction (which you must add to your emulator)
which handles the BBC <-> emulator interface. You will have to write
maybe two/three functions yourself, to handle conversion between the
data types and Beeb memory layout I use and the corresponding way your
emulator does things, but it won't be anything too tough.

--Tom