Date   : Thu, 19 Mar 2009 23:37:09 +0000
From   : jgh@... (Jonathan Graham Harston)
Subject: Hardware questions

"Mark Haysman" wrote:
> > During the startup sequence it zeros the IRQ-copy-of-A with interrupts
> > disabled and briefly reenables them. If IRQ-copy-of-A is corrupted it
> 
> So, can you not just blindly put  64K of SRAM with A8-15 controlled by a
> latch from FCFF, and the lower address and data bus connected to simply give
 
Yes.
 
> you 64K of extra paged RAM? Will having RAM at FDFE and FDFF confuse the OS?
 
No, because the "test hardware" has to assert IRQ after RESET to
generate an interupt and cause the IRQ-copy-of-A to be corrupted.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
RISC OS Choices System - http://mdfs.net/Software/RISCOS