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From: Jan Panteltje <alien@comet.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Zilog stopping Z80 production
Date: Sat, 27 Apr 2024 14:32:57 GMT
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On a sunny day (Sat, 27 Apr 2024 13:57:05 +0200) it happened Gerhard Hoffmann
<dk4xp@arcor.de> wrote in <v0ip6h$1tn2$1@solani.org>:

>Am 27.04.24 um 12:39 schrieb albert@spenarnc.xs4all.nl:
>
>> Motorola was much better in this respect. Peripherals are accessed
>> by handshake. So you could  put a longer delay iff the peripherals
>> are slow.
>> 
>> I remember spending 2000 guilders in around 1980 for 16 K ram
>> for my Z80.
>> Just to discover that code in this ram couldn't run, because the
>> Z80 was too slow. Only useable for data.
>
>The other way around. The RAM cycle time was too slow for the
>Z80 because of the DRAM refresh cycle after the instruction fetch.
>And there was a /wait input on pin 24 if your bus logic was
>unable to keep up with the Z80. Looks like handshake for me.
>
>My first 64K*1 DRAMs did cost DM 64,00 each - which was quite a
>sensation (NEC or Hitachi). And of course, my system got
>the the first usable 8" DSDD floppy drives and ran CP/M.
>I'm pretty sure that the instructions were in DRAM.
>There was no ROM after booting at all.
>
>I did the CP/M port with a friend. It later turned out that
>the Altos computer was near identical, just patching the
>I/O addresses would have been enough.
>Later I even got a 1MB RAM floppy, powered by 8086.
>(really to do a paid CP/M-86 port  :-)
>
>regards, Gerhard

I used 5 1/4 inch floppies in Kaypro2 format
added a 256 kB RAM disk addressed by the Z80 I/O instuctions.
Added a 'copy floppy to ramdisk' command, and could run from there.
No seek and no r/w times times.
 https://panteltje.nl/panteltje/z80/system14/diagrams/index.html
scroll down to 
 Ramdisk card:
 diagram part 1
 diagram part 2
 component layout
 timing waveforms
Wrote my own CP/M clone.