SIMM, Address Lines Order? - test-drb@ccmp.vtda.org

27 Sep 2005

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Subject: Re: SIMM, Address Lines Order?
   From: Scott Stevens <chenmel at earthlink.net>
   Date: Mon, 26 Sep 2005 18:24:22 -0500
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

On Mon, 26 Sep 2005 10:35:16 -0400
Allison <ajp166 at bellatlantic.net> wrote:

  Tim Olmstead wrote a Z80 Dram interfacing manual
thats around the net
 and cover simms as well as the ram on them. Very useful.  I have an 
 electronic copy locally if needed. 

The Z80 has DRAM refresh functionality built right into the processor,
if I'm remembering right. 
You remember right but there was a gotcha.  the Z80 refresh was only 7bits
and about half the 64k drams requried a 256 (8bit) refresh.   the solution 
was with later parts you could do cas/ only refresh and that used the Drams
(later parts and those used for simms) internal counter for refresh address.

Allison