From: ted@telematics.com (Ted Goldblatt) Subject: Re: 70ns or 60ns RAM with a 486/66: does it matter? Date: 8 Jul 1993 12:22:07 -0400
In article <1993Jul7.231015.14986@mnemosyne.cs.du.edu> jgreene@nyx.cs.du.edu (Justin Greene) writes:
>Having ram thats faster than your system can use cannot hurt anything (I
>think) but your budget,
This is not (always absolutely) true. On a (non-PC class) memory
system we built, a change from 100ns DRAM to 80ns DRAM (because we
couldn't get the slower ones anymore :-)) caused the memory to fail.
The reason was that the faster RAMs have better (faster) setup and
hold timings, and the board in question had some gliches (or some
other nastiness) that were not noticed by the slower RAMs, but which
were treated as real by the faster ones. As our stuff tends to be
much better designed than most PC hardware (worst case analysis,
etc.), I would not be at all surprised if problems of this sort could
occur on PCs, which tend to be designed(?) to more of a "if everything
breaks our way, it'll work" standard.
> however, if you keep future upgrades in mind, it
>may be worth spending a few xtra bucks now and not having to buy a new
>chips later. There is also a difference between what the machine requires
>and what would make it happiest. A machine can usually run with slower
>ram but will use wait states. Find out the fastest ram the machine can use.
>
In terms of upgrades, I would not make the assumption that RAM could
be moved to another motherboard (the memory structure might be
different, for example). It does seem to make sense to get RAM
as fast as is needed for the fastest processor that you might ever
want to use in that motherboard.
ted
--
Ted Goldblatt Ted.Goldblatt@telematics.com (305) 351-4367
Telematics Intl., Inc. Ft. Lauderdale, FL