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From: shap@sfsup.UUCP (J.S.Shapiro)
Newsgroups: comp.sys.mac
Subject: Re: 120ns vs 150ns SIMMs?
Message-ID: <2223@sfsup.UUCP>
Date: Tue, 20-Oct-87 00:15:58 EDT
Article-I.D.: sfsup.2223
Posted: Tue Oct 20 00:15:58 1987
Date-Received: Wed, 21-Oct-87 07:14:50 EDT
References: <162@PT.CS.CMU.EDU>
Organization: AT&T-IS, Summit N.J. USA
Lines: 28
Summary: How to tell speeds of SIMMs

In article <162@PT.CS.CMU.EDU>, fryd@G.GP.CS.CMU.EDU.UUCP writes:
> Is it possible to tell by human inspection if a SIMM is 120ns or 150ns?
> 
> I have heard that the MAC II requires 120ns memory.

It does require 120ns SIMMs.

> The chips on the 256k SIMMs have the following numbers
> on them:
>      NEC Japan
>      8707EK06
>      41256-15
> 
> Does the "-15" mean that these are 150ns parts?

Sorry Michael. You have 150ns parts. In general the number you want is the
41256-xx number. This number describes both the layout of the ram
(i.e. 256k x 1 vs 64k x 4) and the speed. The numbers will typically trail
off with the two xx digits being one of the following:

	-10	100 ns parts
	-12	120 ns parts
	-15	150 ns parts

I do not know what is done for faster RAMs.

Jon Shapiro
AT&T