RE: Subing EZ80 microcontrollers for Z80A cpus

Fair question... I was specifically thinking 'multigame' type setups since
we know we have timing margin on the memory in that case. (Even if only to
eliminate all the heat from that army of 2716's on the ROM board a multigame
type ROM replacement is a good idea, IMHO.)
 
I suppose it would be easy enough to test-- see how fast the crystal on a
'stock ' CPU board can go without the security chip before failing, then
swap in an original security chip and see if it'll still work.
 
Thinking about it more, even 450ns 2716's are good for ~2MHz... A Z80
probably isn't hitting memory much faster than 2x the instruction rate, so
from an 8MHz crystal (4MHz Z80 clock) I bet there's probably 50% margin in
the EPROMs still. (I doubt any TTL in between them and the Z80 would amount
to no more than another ~100ns at most, so speed-ups in the 25% range would
seem possible at first glance. Security chip being the unknown there and
the devil is always in the details...)
 
If I get done with my contracting work to-do list for the day I might see if
my ST is still running and just swap in a 10MHz xtal and see if it works.
;-)
 
-Clay

  _____

From: owner-vectorlist@vectorlist.org
[mailto:owner-vectorlist@vectorlist.org] On Behalf Of Chris Brooks
Sent: Sunday, December 04, 2011 11:37 AM
To: vectorlist@vectorlist.org
Subject: RE: VECTOR: Subing EZ80 microcontrollers for Z80A cpus

Just throwing this out there - will the protection chip handle the speed
increase since it's essentially regenerating the addressing? Or are the
implementations talked about here are complete overhauls with unprotected
EPROM code?

Chris Brooks

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Received on Sun Dec 4 14:56:54 2011