MEM11 update

[Guy Sotomayor]

> On Feb 8, 2016, at 12:43 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
> 
>> From: Guy Sotomayor
> 
> 
>> I also wanted to get folk's opinion on the need to actually produce an
>> S[P]C form factor board. ... is it OK to have the MEM11 be outside of
>> the 11/20 chassis and connect via BC11A (my replica) cables?
> 
> Well, that's going to up the cost; for some people, that might be an issue.

The reality (unfortunately) is that no matter what solution I take, it’s not
going to be inexpensive.  The reality is that an SPC board will be more
expensive because of the gold edge fingers.

The other thing is that the boards will be fully assembled.  Except for some
connectors and the UNIBUS transceivers, everything else is surface mount.
I’m still crossing my fingers that I can keep within the 208 pin PQFP for the
FPGA and not have to move into a BGA part.

> 
> Also, I dunno if there are people out there with table-top 11/15's-20's (they
> did exist BITD, I worked with a table-top one), but for them, an additional
> box might be a hassle too.
> 
>> That's assuming of course that the power requirements for the MEM11
>> can be fulfilled by a single SPC slot. ... in the worst case, it may
>> require splitting the MEM11 functionality across multiple boards.
> 
> I guess I don't see the harm in making it two SPC (quad) boards? A flat cable
> or two to connect across (I dunno how extensive the interconnect requirements
> between the halves would be, and I have forgotten what the inter-slot
> interconnect capabilities of an SPC backplane are - ISTR that it has some
> bussing on the F section pins) would be easy and cheap.

See above re: gold edge fingers.  I was originally thinking that if I do have to
split the board up, that I’d make them completely independent.  But that has 
the issue of requiring 2x the number of UNIBUS transceiver parts (which are
all but unobtainium as of now).  One of the things that drives up the power (and
board area) are said transceivers (and level shifters, etc).  If I could come up
with a reasonable alternative for the SPC version, that may work.  But that’s
all in the future at the moment.

TTFN - Guy