64 pin SIMM (Mac IIFX) Specs?

[Tony Duell]

> If the DIN and DOUT are common on the MB, and I use 16M X 4 chips, I 
> assume that I should either use the DIN pin or the DOUT pin on the 
> SIMM but not both?  Using both could result in different length 
> datapaths which remerge, possibly causing interference from slightly 
> out of phase signals.  The difference in length probably wouldn't 
> affect the timing much, but still...

My guess is that if they are linked, they will be linked by short tracks 
near the SIMM sockets. And you'd be linking them with short tracks on the 
SIMM PCBs. Considering that a light-nanosecond (in free space) is about 1 
foot, and that the velocity factor of a PCB is going to be around 0.6, I 
would guess about 8" of length difference would give 1ns of timing skew. 
I don't know how fast that amachine runs, but I would think you'd have to 
have a right stupid layout for using both pins to matter much.

-tony