sicc said:
I'm looking for a motherboard that supports twin AMD processors.
Socket AM2.
All I can seem to find is Opteron based mobo's.
Any ideas?
There shouldn't be any with dual AM2.
http://www.amd.com/us-en/Processors/ComputingSolutions/0,,30_288_13265_13295^13340,00.html
"All AMD Opteron processors feature three 16-bit HyperTransport technology
links running at 800MHz, and theoretically capable of 1.6 gigatransfers per
second or 3.2GBps of bandwidth in each direction.
In a single-processor configuration, the links are non-coherent – all three are
available for connection with system I/O components.
In a multi-processor configuration, one must be coherent, leaving the others for
I/O responsibilities. The coherent link allows each processor to access another’s
memory. Thus, an AMD Opteron processor 800-series CPU, designed for four- and
eight-way configurations, needs three coherent HyperTransport technology links
to communicate with its neighboring processors."
It is the missing coherent protocol, that should prevent an ordinary
AM2 processor, from working with a second one. A coherent protocol
ensures that both processors know where to find the current valid
copy of a piece of information. It is either held in one of the
processors internal caches, or in system memory, and the protocol
is there to control it.
Opterons have one to three coherent links, and a pricing structure
that recognizes the importance of coherence to building big servers.
That is why there are three columns for the Opterons, in this pricing
chart. A hefty price for a coherent link.
http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_609,00.html?redir=CPT301
"Coherent" is mentioned in this chart of Opteron quad cores.
1 coherent = 2 way scalable. 3 coherent = 8 way scalable.
I believe the 2 or 8 refers to sockets, so you could have
up to a 32 core system via these (8 quad cores).
http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_8796_15226,00.html?redir=CP8501
To see how big an 8 way system is, take a look at this product.
There are two motherboards. The motherboard are spaced apart by
two riser PCBs (no components, just FR4 and contacts on the ends).
The riser PCBs are circuit paths for two coherent links. (See if
you can spot the error in the block diagram. First, eliminate the
memory sticks and their associated memory bus, as they aren't
Hypertransport. Each processor should have three remaining
Hypertransport links, to make the interconnect between the eight
processors. I think the top two processors should have a link
each, left over.)
ftp://ftp.tyan.com/datasheets/d_s4881_104.pdf
Paul
