DEC M8350 - KA8E posibus interface

[Joe R.]

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
>