DEC M8350 - KA8E posibus interface

[Allison]

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
>>