Re: [oc] Modular FPGA board

[Marco Antonio Simon dal Poz <mdalpoz@lsi.usp.br>]

On Wed, 22 Nov 2000, John Dalton wrote:

> The idea is to build a basic motherboard with
> FPGA, power supplies, programming and a programmable
> oscillator (with maybe a second FPGA and a PCI connector).

Very good idea, but is there some open core with PCI master/target
interface? I don't think so. Are you planning to use comercial chips for
PCI interface?

> Instead of peripherals, it will have a whole bunch of 72
> pin SIMM sockets on it.  Peripherals can then be built as
> modules and plugged in.  SIMMs have the advantage of
> 1) being cheap
> 2) having the potential to go fast (after all, they build 133MHz memory
> modules)
> 3) Not incurring the cost of a socket for each module.
> 4) Using SMT, a lot can be crammed on a SIMM.

Yes, but I am not sure about the maximum bandwidth that a signal can reach
by using 72 pin SIMMs. Notice that to achieve broadband signals, RDRAM
uses a different kind of connector (RIMM) and the circuit has smaller
databus width and is completely shielded.

> Is anyone aware if such a thing already exists?  After coming
> up with this idea, I did a web search and located SIMMstick
> (http://www.simmstick.com).  This is a similar idea for micro
> controllers,
> using 30 pin SIMMs.  As far as I can see, nothing similar exists
> for FPGAs.

AFAIK, nothing similar exists for FPGAs.

> More questions:
> 1) Standard SIMMs use 1.27mm thick PCB.  Is it possible
> to fit 1.6mm PCB into a 72 pin SIMM?  1.6mm PCB
> is much easier to get.

1.6mm PCB doesn't fit into a 72 pin SIMM slot. And here in Brazil, 1.27mm
is much easier to build (BTW, I have never seen a 1.6mm thickness PCB).

> 2) Are 72 pin SIMMs still widely available around the world,
> or have they been superseded by DIMMs?  (I would like to
> keep to SIMMs, as it is difficult to align contacts on both
> sides of a home built board.)

Again, here in Brazil it's becoming difficult do find SIMMs, and when
someone is able to sell or trade SIMMs, it costs more than the double
price of the DIMMs of the same memory capacity.

Greetings from Brazil!

	Marco Antonio