Date   : Wed, 19 Oct 1994 12:38:52 +0100 (BST)
From   : clr1@...
Subject: BBC: Disk Handling

Thanks to all the people who helped me with the keyboard; I'll have 
another stab at it tonight.

I want to start a bit of a discussion about disk handling. I've been 
talking to Mark Cooke about this off the list, but I wanted to throw it 
into the pot.

Here's my two cents worth!

My gut feeling is that an emulator should emulate the *whole* machine, if 
possible. That means disks too. So I think that if you have a BBC 
emulator, you should be able to stick BBC disks in it. What I'm hoping to 
do is set up my emulator to read BBC disks (which looks like it might not 
be easy) and then just to fudge the ADFS read/write sector routines (or 
even just intercept the OS calls). Then when ADFS tries to read a sector, 
it will read it from the BBC disk in my PC drive. That means all the 
filing system will still be taken care of by ADFS and BBC disks will work 
fine.

My other idea was to set up a virtual hard disk on the PC; just a big 
long file. Then I would intercept ADFS calls to read/write sectors to 
that as well, and hey presto - ADFS would do all of its own filing on a 
hard disk too. I'm not sure what the maximum HD size on a BBC was, but it 
would be interesting to have a 16Kb BBC B with a 1Gb, 2Mb/second hard 
disk fitted!

+-------------------+-------------------------------------------------+
| /-- |_| /-- | (~  | "And the driving is like the driving of Jehu,   |
| \-- | | |   | _)  | the son of Nimshi, for he drives furiously."    |
+-------------------+-------------------- Second Book of Kings 9 v20 -+