DEC M8350 - KA8E posibus interface - test-drb@ccmp.vtda.org

22 Jun 2005

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:
   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). 

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
> 