a classiccmp electronics project?

From: Dwight K. Elvey <dwight.elvey_at_amd.com>
Date: Fri Jul 30 18:00:43 2004

>From: ard_at_p850ug1.demon.co.uk
>
>>
>> Tony wrote...
>> > Yes, modern SRAM is fast enough. But that's 'easy' in theory. Firstly you
>> > have to have some way of switching the SRAM between the device and the
>> > loader
>> Dual port SRAM is one answer. Or, I'm not sure what the power on test in
>
>Sure, but have you looked at the price :-)

Hi
 You use single port RAM with an output buffer ( could even be
a 7404 but it would most likely need a 3state control, '240 or '244 ).
You hold the machine in reset while you transfer data to the
RAM ( It doen't make much sense to do it on the fly with
the machine actually running ).
This isn't much more complicated than a memory board.
Dwight

>
>> microcode does on the MX's, but my guess is it doesn't touch the add-on
>> microcode. The loader roms probably aren't touched either until called from
>> the front panel. If the RPL stuff is turned on, it may though. I think the
>
>OK. I was thinking about the microcode ROMs in an HP9810 (somethign that
>_I_ am working on, and those are most certainly 'hit' as soon as INIT is
>deaseserted and the microocde program counter starts to change. I prefer
>to think of general-purpose solutions (i.e. somethign that will replace
>every 256*4 ROM), rather than soemthing that works only in specific
>machines under specific circumstances.
>
>-tony
>
>
>
Received on Fri Jul 30 2004 - 18:00:43 BST