22 Jun
2005
22 Jun
'05
9:15 a.m.
Top posted for size reasons...
I do not know for sure that 7bit refresh is required. It's likely
(not totally ceratin) that if you only using part of the array
you will require 8 bit refresh anyway.
known 7bit refresh 64k DRAMS, NEC, Mitsubushi, Hitachi HM4864
Known 8bit refresh TI, Moto(they also had hidden refresh).
There may be others.
Allison
Subject: Re: DEC M8350 - KA8E posibus interface
From: "Joe R." <rigdonj at cfl.rr.com>
Date: Wed, 22 Jun 2005 08:50:05 -0400
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
At 11:58 PM 6/21/05 +0100, you wrote:
Tony,
This is good info. Someone should post it as a mini-FAQ.
Do you have any info on which ones used 7 bit refresh and which ones used
8 bit refresh?
Joe
>
>I have personally replaced the odd 4116 with a 4164 as I've just
>described and had no problems. Maybe I've been lucky in finding 7-bit
>refresh chips (which are the more common type), maybe it works anyway.
>
>> serious wad of new 4164s from COMBOARD stock, but 128Kw of 4116s (8 x
>> 12) is more than I have lying around.
>>
>
>-tony
>
Also...
does anyone know about the differences between 4116 and 4164
chips enough to answer the question if one could use 4164s as long as
one a) prevents the non-TTL supplies from reaching the chips (modify
What you need to do is isolate pins 1 and 8 from the board and reconnect
pin 8 to +5V IIRC
4116 4164
1 -5V N/C
8 +12V +5V
9 +5V A7
That leaves the extra address line tied high, so you only use 1/4 of the chip
board, modify sockets, modify pins...) and b)
possibly tie up or tie
down the extra multiplexed address input. Can you refresh 1/4 of a
4164 and have just that part stay refreshed? I ask because I have a
There were 2 types of 64K DRAM. One of them used 7 bit refresh (same as
the 4116, on the same pins), the other, older/rarer one need all 8
address lines to be used for the refresh (this was a royal pain on
Z80-based machines, where the CPU provides a 7 bit refresh only).