[comp.sys.mac] 120ns vs 150ns SIMMs?

fryd@G.GP.CS.CMU.EDU (Michael Fryd) (10/13/87)

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.
I have also heard that some 256k SIMMs are 120ns and some
are 150ns.   How do I tell
from looking at a SIMM if it is suitable for a MAC II?

In particular, I have some 256k SIMMs that came out of
a MAC SE when it was upgraded with 1 meg 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?
I had heard that all MAC SEs came were supposed
to come with 120ns parts?

		- Thanks for any advice.
		  Michael Fryd

Michael.Fryd@cs.cmu.edu

shap@sfsup.UUCP (J.S.Shapiro) (10/20/87)

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