Date   : Fri, 20 Mar 2009 00:32:01 -0000
From   : jumbos.bazzar@... (Mark Haysman)
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.

Nice, I had always thought that was the case, but reading that about the 
test hardware got me worried for a moment!

It's also useful to note that you can make the OS jump to code that's paged 
in at FDxx if you wanted to...do all versions of the OS do that?

Mark.