64 pin SIMM (Mac IIFX) Specs?

[Teo Zenios]

----- Original Message ----- 
From: "Jeff Walther" <trag at io.com>
To: <cctech at classiccmp.org>
Sent: Tuesday, September 06, 2005 2:20 PM
Subject: Re: 64 pin SIMM (Mac IIFX) Specs?


>
> >YEs, that was the idea. It's no use if you want to link the data pins to
> >a bidirectional bus.
>
> >I suspect the _real_ reason for it was that there was a spare pin on the
> >package and it didn't ever make life more difficult to have separate DIN
> >and DOUT pins (oyu could just strap them together externally if you
> >wanted a bidirectional data pin).
>
> I'll be getting a IIfx on Thursday and I can confirm (I hope) that
> the DIN and DOUT are common on the mother board at that time.  Your
> advice has given me hope that this is much more doable than I feared.
>
> If they're tied, then I should be able to build a 16MB SIMM using two
> 16M X 4 chips.  My concern was that the X4 chips do not have separate
> DIN and DOUT and I wasn't certain if the IIfx actually needed the
> separation.   I think I have some 16M X 1 chips which would work in
> either case, but my supply of 16M X 1 chips is much smaller.
>
> 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...
>
> It would still be handy if someone has a mechanical drawing of the 64
> pin SIMMs.  I can derive it from a physical example, but I'm less
> likely to get the actual center measurement and tolerances correct
> that way.  Hmmm.  I'll check around and see if any of the socket
> manufacturers are still selling a 64 pin SIMM socket.  If so, I
> should be able to derive the SIMM dimensions from the socket
> datasheet.
>
> Jeff Walther

Are you planning on selling 16MB SIMMs or just making a few for personal
satisfaction?