kushall.Henr@XEROX.COM (07/22/89)
Subject: 7 bit refresh
RE:
>I need 64Kx1 dynamic RAM chips, like 4164's. They need to be 100 ns.
They need to work with 7 bit (128 cycle) refresh. I have called 20
different people (really! I counted!). Every single person I talked
to apparently didn't know what I was talking about. As I talked to
them, I could see (even through the phone!) this strange blank look
come across their face.
Am I the only one in the world who understands the difference between
7 and 8 bit refresh??? Am I going to have to buy 256K RAM chips and
waste 192K of RAM to make this project go???
Well I was able to locate data for 4 mfg of 64K DRAM and all but Toshiba
were 8 bit refresh. Note that ALL the data sheets for 256K DRAMS list them
as 256 refresh cycles/4 ms (A0-A7) including Toshiba. * bit refresh seems
to be the industry standard for 64K and 256K DRAMs.
The following info is from the respective mfg data sheets:
Toshiba: TMM41164P-2 128 refresh cycles/2ms(A0-A6) but only 120 ns
NEC: uPD41464-10 256 refresh cycles/4 ms (A0-A7) 100 ns
Hitachi: HM50465P,CP Series 256 refresh cycles/4 ms
TI: No longer lists 64K DRAM but the old(86) data sheets lists the TMS4164
as 256 refresh cycles/4 ms (A0-A7)
Ed Kushall