First you locate some decent memory products for your build.
The motherboard part will come easy.
The stated i7 limit right now, is 24GB, which would be 6 modules
of 4GB each. But try and find some DDR3 4GB modules first. Samsung
has announced some, they are in various QVL lists, but they're not
available at retail.
SAMSUNG M378B5273BH1-CF8 DDR3 1067 4096MB DS SAMSUNG K4B2G0846B-HCF8 8(7-7-7-20) 1.5 * * * *
The funny part is, you can find DDR3 SODIMM modules at 4GB density, but
not a regular DDR3 DIMM.
The Core i7 may not support ECC, so your large memory machine would
not be protected against trivial single bit memory errors.
Currently, your most practical solution, is one of the X58 boards
with six memory slots (memory interface is on the processor itself,
and not defined by X58). Buy some (available) 2GB DDR3 modules
without ECC. Total memory is 12GB and with decent pricing compared
to the pricing on 6*4GB modules. Those 4GB modules, when they come out,
might cost you $4200 total or so. The 6x2GB plan will be cheaper.
Also, for Core i7, Intel states that Vdimm should not exceed 1.65V.
The nominal is 1.5V. Some enthusiast memory products in the past
(for other motherboards), have used higher voltages to attain
their memory specs. So a lower voltage product is what you'd be looking
for. If you find 3x2GB memory kits, they would be made specifically
for Core i7 (there'd be no other market for them), so they're likely
to stay at or below 1.65V. I understand some people are running
their memory at higher than that, but for how long...
If you were serious about the RAM, then a server board with FBDIMMs
is one way to get it. They have ECC capability. The last time I looked,
I could find a motherboard with room for 192GB. Using lower capacity
modules, would drop the price of populating such a motherboard. (There
isn't quite the premium for the lower density FBDIMM modules.)
(Clarksboro chipset, 192GB max via 24x8GB FBDIMM. Use 24x1GB instead)
http://www.supermicro.com/products/motherboard/Xeon7000/7300/X7QC3.cfm
(5400 based. Stuff 16x2GB FBDIMMs in it.)
http://www.tyan.com/product_board_detail.aspx?pid=560
Paul