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The problem with prefetch

The problem with prefetch

Posted May 24, 2011 23:48 UTC (Tue) by pphaneuf (subscriber, #23480)
In reply to: The problem with prefetch by Cyberax
Parent article: The problem with prefetch

The NEC SX-4 had 16 gigabytes of SRAM as its main memory. It didn't really have any CPU cache (only something like 32KB of instruction cache). That was a nice way of not having to deal with cache coherence issues in an SMP system.

It also had a 256 bytes wide memory bus (compared to the typical 64 bits).

Serious hardware, that. :-)


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The problem with prefetch

Posted May 25, 2011 10:03 UTC (Wed) by kruemelmo (guest, #8279) [Link]

Now tell us something about power consumption as well please.

The problem with prefetch

Posted May 25, 2011 10:23 UTC (Wed) by dgm (subscriber, #49227) [Link]

And some performance numbers would also be appreciated.

The problem with prefetch

Posted May 25, 2011 11:36 UTC (Wed) by Cyberax (✭ supporter ✭, #52523) [Link]

http://www.ai.mit.edu/projects/aries/papers/vector/hammon...

Power consumption is 123KVA for 32-core version, performance is around 2GFLOPS per core for vector operations.

The problem with prefetch

Posted May 25, 2011 19:50 UTC (Wed) by wazoox (subscriber, #69624) [Link]

Impressive machine, not even puny by today's standard...

The problem with prefetch

Posted May 25, 2011 22:05 UTC (Wed) by pphaneuf (subscriber, #23480) [Link]

Yeah, I don't know about the power consumption, but while it would put out a good deal of heat, the SX-4 was the first of the SX series to be air-cooled. I'm not sure if the SX-3 used SRAM or DRAM (it was before my time), but that one was water-cooled.

While the vector performance was amazing, it was pretty sluggish for scalar stuff, so we didn't even use it for compiling, it was too slow.

Not saying that this is the end-all, be-all (the SX-5 traded in the SRAM for DRAM, and in exchange got 128 gigabytes of it, which was a whole lot in 1999 or 2000!), but just pointing out that it's been used on supercomputers (and I've used them), and it didn't require liquid nitrogen.

Here is a photo of one of the four SX-5 I helped look after.


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