21MX proms (per request)

John Robertson jrr at flippers.com
Mon Sep 7 10:32:54 CDT 2015

On 09/06/2015 2:00 PM, Alexandre Souza wrote:
> Jay, no one is pin compatible, I always make adapters. But at least I make
> it work :D
> 2015-09-06 16:00 GMT-03:00 Jay West <jwest at classiccmp.org>:
>> Alexander wrote...
>> -----
>> Intersting to note: many times i have used eproms in place of these proms.
>> Usually, flash parts are faster, so better suited to the task.
>> -----
>> Loader roms:
>> You may be able to get by with that on loader roms. I've never found
>> eproms that were functional & pin compatible. What ones did you use for the
>> 1K variety?
>> Microcode:
>> I doubt seriously the eproms would be stable for microcode. HP specs 5ns
>> speed parts for the microcode; what eproms work and can hit those speeds? I
>> suspect this is one of those "might seem to work" but is a really bad idea.
>> J
As Jay points out, it is the access speed required by the device you are 
substituting the EPROM for a ROM/PROM that counts. In some cases the 100 
to 400ns access speed of EPROMs won't matter (clock of under 1mHz for 
400ns 2716s to around 4mHz for 100ns EPROMs), but if you are running 
10mHz or faster reads then I suspect you will have problems unless you 
find faster devices than EPROMs for your substitute ROM/PROM...

John :-#)#

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