kony wrote:
> On Thu, 12 Apr 2007 10:43:30 GMT, "Hank" <Hank@Hank.net>
> wrote:
>
>> this is a motherboard memory specifications, do I read that as
>>
>> up to 32 gig of ddr2 memory running at 533
>>
>> or
>>
>> up to 16 gig of ddr2 memory running at 667?
>>
>>
>> why would it have this limitation? I would think it wouldn't matter (to the
>> motherboard) what the speed was
>>
>> thanks
>>
>
>
> The same is true of all motherboards whether spec'd or not.
> The more memory you install the lower the stability margin,
> and if the margin drops low enough it will require reducing
> the memory bus speed or raising the timings to retain
> stability (and/or registered or buffered memory). However,
> some boards conveniently avoid this by merely having too few
> slots to install that much, or their bios logic
> automatically changes the timings to compensate.

The OP may be referring to a 5000 series server motherboard, with
FBDIMM memory. FBDIMMs are serially connected, at extremely
high speed. They are effectively point to point. The second
FBDIMM in a channel is daisy chained to the first, meaning
there is the "thru-delay" via the AMB on the first module,
before you get to the second.

The serial interconnect on the FBDIMM, is synchronous to what
the memory chips are doing. If DDR2-667 memory is used,
the serial interconnect is at 12 x 333MHz, for a 4Gbit/sec
interconnect to controller or to the next FBDIMM.

http://en.wikipedia.org/wiki/FBDIMM

I cannot figure out a reason why one of those would have
a stated capacity versus speed issue. Being fully buffered,
the motherboard cannot "see" the load from the memory chips
on the module. So it shouldn't matter. The Tyan advertising
seems to relate size to speed, but the Supermicro advertising
for similar products doesn't.

Tempest i5000XT (S2696)
http://www.tyan.com/product_board_spec.aspx?pid=43

"Maximum of 32/16GB of DDR2-533/667"

So it is still a mystery to me, why they state it that way.
And the user manual does not elaborate further on the issue.

Paul