Rich said:
Seems like they are just coming out of the dark ages in terms of this.
Dual-core is the best they can offer. Why aren't some machines
available to
consumers made so you can plug in up to 10 processors, etc?
I figure the limitation is Windows, but I'm not sure.
The limitation is simply cost. The processor vendors
and motherboard manufacturers have built commodity hardware
aimed at the one to two socket market. Four socket
systems are significantly more than two times more costly
than two socket systems, and systems with more than four
sockets are proprietary designs requiring significant
(and expensive) engineering support to build (e.g. think
L3 cache controller ASICS, fancy cross-bar switching
networks, NUMAlink, CRAYlink, NUMA-Q, etc).
Just for example, the current opterons have 3 HT links
and the HT bus has a 3-bit address field (allowing eight
addressible entities). Given the need for at least one
PCI tunnel/LPC/Southbridge, that means a processor
can communicate with only 6 other processors.
That said, any consumer with the $$ can buy a 1024
processor SGI Altix system anytime they wish. Just
make sure you have a 1000A service and good HVAC.
You can also expect that with quad core processors available
in a couple of years, a quad-socket quad-core system is
an effective 16 processor box; this will be pretty close
to commodity in 4 years.
From a software perspective, some operating system vendors charge
significantly more for operating systems capable of effectively
utilizing more than four processors. Windows, for example.
Linux, on the other hand, will cheerfully run on the
aforementioned Altix. It is quite challenging for
operating software programmers to scale the operating system
for larger processor counts, as the standard synchronization methods
(e.g. spinlocks) seldom scale well past four or eight processors.
scott
