Date   : Sun, 23 Jul 1989 12:32:00 EST
From   : "Architecturally, Z-80 can be made to run@100MHz!"
Subject: Uh-oh.... (was 7-bit Refresh)

Well, I am a currently enrolled student living in the college-provided
housing (a.k.a. Dorms).  It so happened that I had to move almost every
semester and go home to Korea over the summer, which means that having
databooks that fill a 4-by-six space was a drag, which lead me to "weed
out" duplicate and "obsolete" copies.  I knew I shouldn't have, but
the "friends (like the recent popular music proclaims)" forced me to.

I say, never trust your "friends!"  I just realized that most companies have
decided to cut back (or discontinue) on their 64-k DRAM products!  The only
databooks that list them are the old ones that I was about to have replaced!
Which means, while the companies ARE still producing 64K DRAMS for
"maintenance" purposes "ONLY," and those parts are available in the market,
I don't have any data on them!

256-K DRAM's (even 64K by 4) are ALMOST WITHOUT EXCEPTION 256 cycle refresh,
which means that they can NOT be used (with ease) with true Z80 (*&D#%ing,
eh!).  MY SUGGESTION, at this point, would be to use 32K by 8 STATIC RAMS
(Hey, don't gasp...)!!!  They are only $15 each, at most, these days int the
mail-order world, and are getting faster by the day.  Pseudo-static RAMS
are not a bad idea, either.

For your information, Hyundai made 256-cycle DRAMS, and Motorola and Oki
made 128-cycle DRAMS.  So did Mostek, but they merged with SGS-Thompson,
and no DRAMS in their databook!  All 128-cyclers are 2mS refresh.

                         John Shin

P.S.  Like I said, it would be also a good idea to get the brand of the
64K parts from the shop and ask the manufacturer, although telling a
256K chip that it is a 64K ship isn't such a bad idea, either.