PC1066 RDRAM vs. DDR SDRAM

Brad wrote into send us his "Comparison of PC1066 RDRAM vs DDR SDRAM. Quote - RDRAM is considerably more expensive that DDR SDRAM, and up until now the 100MHz PC800 specification didn't do well in comparison. Just recently 133MHz PC1066 was launched, and is now officially supported by the new Intel P4 and the Intel 850E core logic chipset, but this time promises to bring memory performance to the next level."

Comments

Bzzzt!

[popular]

Intel's i850 does not support PC1066 officially, and parts of that speed have only been validated since the release of i850E. Officially, the chipset simply supports a FSB that would complement that speed, if the two busses ran synchronously. Seen here:
http://www.theinquirer.net/24050203.htm

That said, PC1066 has been tested before (can't find the article at Ace's Hardware), and the bandwidth of DRDRAM appears to compensate quite nicely for the P4's generally lousy architecture, as does its increased cache size (now 512k L2).

The fix is in.

[blair1q]

What a bogus comparison.

PC2100 is old news, and 1066 RDRAM is just being released.

The proper comparison would have been against PC3200, or PC2700 at least.

N.B., I've been using PC2700 in my machine for two months. PC3200 is about 33% more expensive.

--Blair

Bandwidth is nice. Latency is evil...

[Svartalf]

While the benchmarks he ran show nice bandwidth figures (Negligible, really, in light of how expensive that RDRAM is- if that's all this new memory spec can do, well...) it doesn't tell the whole story. There's bandwidth and then there's latency. In the case of RAMBUS, there's more latency involved with the access of the memory than with DDR SDRAM- latency that may eat some or all the bandwidth gains you see there when you start doing something other than benchmarks. If it's not really much faster (Sorry, it's not when you start looking at the bigger picture), why are you spending 3 or more times for it?

I think I'll wait

[NickRob]

I think I'll wait until The guy who wrote this hardware report writes on this issue.

Let's discuss CPU cooling & SMP

[Jeppe Salvesen]

CPU cooling is much more relevant to performance than a 2% memory bandwidth gain.

Basically, CPU cooling has been hitting us for a good while.

From an article about a bigass Beowulf cluster running Transmeta processors, you have Wu-chun Feng of the Los Alamos Labs stating

The continued tracking of Moore's law will result in the microprocessor of 2010 having over one billion transistors and dissipating over one kilowatt of thermal energy; this is considerably more energy per square centimeter than even a nuclear reactor.

Oh my. So - what else can we do to stop this trend? Relatively slow multi-processor machines. If we keep working on multi-threading our applications, we might be able to make a computer with 8 1ghz efficient chips outperform an 8ghz Moore-compatible Intel hype-chip-based system. Really. Multi-processor machines have traditionally been too expensive for the desktop. The software people have not spent a lot of time making sure that the regular end-user applications scale well across several processors.

Take something like a web browser. Given a bit of wizardry (obviously, we need to consider concurrency and critical sections), you could have separate images downloaded and processed by separate processors. Your flash ad would run on another processor.

Frankly, I'm wondering what's stopping us from using this approach to increasing performance? Is this like the fact that OEMs equip the low-end PCs with too little RAM so that Joe Shmoe will buy a new one as quickly as possible, since he does not know that spending 100 bucks on more RAM will make his computer last another year or two?

And, really, as long as the focus is on the gigahertz, do the chip makers really concentrate on making their designs as efficient as possible?