Date   : Tue, 23 Aug 1994 12:31:35 +0000
From   : lamcw <lamcw@...>
Subject: Re: Mine did something! Eeek!

jfid@... (James Fidell) wrote:

;> my philosophy for handling the paged io is to do all the emulation when
;> values are STORED to sheila. therefore any reads from sheila will be 
;> correct and one does not need to 'intercept' the read.

;I'm not sure about this.  It's theoretically possibly for the data to
;change between the write and a subsequent read, even if it's unlikely
;(which would probably depend upon you're emulator implementation).


i wasn't being entirely truthful. i do update IFR after every instruction.
the counters in shiela should strictly be updated after every instruction
in case they are read by a program. i've just remembered that reading one
of the counter locations, resets that interrupt in IFR. gee whiz, what
a nuisance.


;> a really invaluable (but somewhat unheard of) book is 'guide to the bbc
;> roms' by don thomasson, published by melbourne books. there wasn't a hope
;> in hell of me getting this far without it.

;I haven't seen this, even though my boss has promised me several times
;that he'd let me borrow it.  What's it like ?

worth having (see previous reply to james bonfield)


chris lam.