Date   : Fri, 04 Nov 2005 18:14:40 +0000
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: BBC using 3.5 high density format

Pete Turnbull <pete@...> wrote:
> On Nov 4 2005,  0:20, Jonathan Graham Harston wrote:
> 
> > However, the BBC Master runs at 3MHz, so a 41-cycle NMI routine
> 
> Perhaps you're confusing the Master 128 with the Turbo or a 6502 Second
> Processor.  The second processors do run at 3MHz, but the CPU and DRAM
> clock in the Master is only 2MHz.
 
New Advanced User Guide, p30:
 
"1 instruction cycle=0.5us in a BBC model B, 0.33us in Master or
6520 2nd processor, 0.25us in a Master Turbo 2nd processor"
 
but...
 
The Advanced Reference Manual for the BBC Master, p19:
 
"processing is done at 2MHz"
 
which is confirmed by the cuircuit diagram showing phi2 being fed
from 2M on the Video processor.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
 HADFS System Resources - http://mdfs.net/Software/HADFS