Help: Need a Mobo with Max Mem and Some Configuration Help

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I would like to put together a socket 939 system with 8 GB of RAM.  The only
board that newegg mentions that supports 8 GBs are the Abit, but the OCZ Ram
configurer says they only support 4 GB.  I am a big fan of DFI and if the
most 939 boards can support is 4 GB,  I was thinking of getting the DFI
Ultra Infinity board.

I am interested in heavy duty floating point calculations and I am looking
for good recommendations for a motherboard that will overclock.  I am also
thinking of getting a Venus Opertron.  The price seems to increase by
$40/200 MHz.  The 146 at 2.0 GHz might be the best compromise although I am
tempted by the 154 at 2.8 GHz.

I would like to have the fastest system that I can configure, so what do I
need to consider about multipliers before selecting a chip and what about
RAM  speed?  Should I get the fast RAM available or will PC 3200 be fine for
ramping a system up?  I would like to hit 2.8+ GHz using stock cooling.

I am only interested in single processors. I will be running just a box with
just a massive harddisk and CD drive, no monitor.

How do the Opertron's compare to the FX series? I am assuming both chips
will use standard DDR RAM.



Re: Help: Need a Mobo with Max Mem and Some Configuration Help

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You are barking up the wrong tree.

Think of the problem as, "what platform supports 8GB of memory
in a practical way", then take whatever processor results from
that selection. With 4GB total system memory, your choices would
have been a lot more open.

In the Intel camp, the current memory technology is DDR2. There
are 2GB unbuffered and 2GB registered memories available. Four
unbuffered sticks with ECC can be used on a relatively cheap
desktop motherboard, plus your choice of single or dual core Intel
processor. Obviously, you'll need to dig up a datasheet for
the Northbridge on your new prospective motherboard, to make
sure the support is there for 2GB modules. Don't expect
the motherboard manufacturer to have tested 2GB DIMMs.
(975X = 2GB OK, 955X = 2GB OK, 945P = memctrl 2GB OK but
FSB 4GB addr max, 925X = memctrl 2GB OK but FSB 4GB addr max).
I would be searching for a modern 955X or 975X Intel chipset
motherboard. Check the BIOS to make sure the memory remapping
function is present and enabled (that maps around the I/O space
around the 3.5GB to 4GB physical address range).

In the AMD camp, the technology of choice is DDR. If you go to
Crucial or Kingston, and search on an Asus S939 motherboard,
the largest unbuffered DIMM size listed is 1GB. So you can get
4GB max that way. I checked Samsung, and the largest unbuffered
module listed on there is 1GB. You still need the memory
remapping function, to get to use all of the 4GB of memory.

The old S940 motherboards (like SK8N and SK8V) use registered
memory. You could try a 4x2GB registered ECC DIMM config on there.
If you look at the CPU support here, both of those motherboards
support up to a Opteron 250 (2.4GHz). The Opteron 254 (2.8GHz)
is not listed in the supported processors. Due to the level
of BIOS update support motherboards like that get, I would not
screw around by trying to plug a 254 in there, unless your
retailer has a generous returns policy on processors. If you
like this option, contact Asus tech support and get their
opinion as to whether a 254 would work. There are also
1xx series processors for Socket 940, but I don't understand
the logic at AMD, as to what processors are available in
what sockets. Be very careful when shopping.

Check your motherboard here:

An (incomplete) Opteron summary table:,,30_118_8826_9240,00.html

Another solution would be a dual socket motherboard. Basically
each processor hosts four DIMM slots, and if your computing
task can only make use of one processor, the second processor
would be functioning as a simple minded memory controller.
I don't know if you can mix a cheap and slow processor in
one socket, with a fast and expensive processor in the second
socket. Presumably, if they both have the same silicon revision
(like E4 or E6 or whatever), that would increase the odds that
the BIOS would smile favorably on the marriage. That would be
the case, because the memory controller registers would have
the same feature set. I have never read of someone trying this,
so treat the idea as pure conjecture.

Most people would simply use two identical processors on a dual
processor board.

Note that the max memory bandwidth when using the dual processor,
and assuming nodal interleave is enabled, would be 12800MB/sec.

Now, consider the price of DIMMs for a moment. Some of the
2GB DIMMs were $500+ , and I'm willing to bet that the 1GB
registered DIMMs would be a lot cheaper per GB. So, even though
you would be buying two processors, the total computer cost
might still be competitive by buying (8) 1GB registered ECC

In terms of dual socket motherboards, Asus has the K8N-DL and
there is a large assortment at Tyan to choose from.

Tyan also has Intel server boards, and those could well support
a lot more memory.

So those are a few ideas, but at the memory size you are
contemplating, there are plenty of "gotcha" details to
worry about. What you are attempting is not a trivial


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