In The Heat of the PC1066...

By Nebojsa Novakovic BACK FROM COMPUTEX, two PC1066 32 ns RIMMs -- Samsung 256 MB parts -- were waiting for me here in Singapore. You can guess how impatient I was to get them into the Intel 850EMV reference board for some "non-validated" fun.

And there we went: out goes 512 MB of PC800 45 ns RAM and in goes 512 MB of PC1066 parts. When I turn on the system, the expected "non-validated PC1066" message appears, I say "yes, I want to use it" and go on.

Guess what? The Windows XP refuses to continue, saying the system config has changed and Windows needs reactivation. Since re-activation, unlike activation, needs a dial-up modem to call a local M$ number (no broadband here) and I don't keep such prehistoric stuff in the system, I had to call M$ to get the new ID and log into the system. Geez, how much change is this to warrant the reactivation nuissance?

Just replacing two RIMMs with a same capacity, higher-speed grade?

The even funnier thing was when, before that, we swapped DDR400 (PC3200) with DDR266 (PC2100) DIMM on the Asus P4S533 (SiS 645DX) and Windows refused to boot at all on that system (it was a different installation than the RDRAM system).

Anyway, once that was over, we tested the new configuration with both 2.4 and 2.53 GHz (both 533 MHz FSB) CPUs, to not only test any speed-ups with the faster memory, but also to see how well the P4 scales with frequency, assuming the memory is the fastest possible.

Heh, what to expect? The performance delta between 2.4 GHz PC800 and PC1066 versions on the same 533 MHz bus is higher than between 2.4 and 2.53 GHz with the same memory. Except for the Sandra suite with its wavering results, the benchmark results give between 2% and 7% speedup with PC1066 over PC800 on the same P4-2.4/533 - except the PCMark2002, where the benefit jumps to 14% in the memory test. On the other hand, going from 2.4 to 2.53 GHz with PC1066 gives only between 1% and 3% speedup in the same tests.

The benefit is even less if using PC800, since higher-speed CPU will be stalled more with slower RDRAM.

Sandra did give us some inexplicable results due to varied outcomes in every run (there is no way a PC800 system would be faster than an otherwise identical PC1066 in anything).

So, if profiling a truly balanced high-performance P4 system, keep in mind: P4 is very memory speed dependent compared to some other X86 CPUs, and maximising the memory throughput may be more important than getting the fastest CPU speed parts.

Major problem: Samsung 32 ns 256 MB dual-sided PC1066 RIMMs are much hotter than the PC800 45 ns parts - I had to ensure that the casing has a side fan blowing cold air directly at the RIMMs to ensure truly stable long-term operation. So, if paying a premium for the PC1066 (and that premium is hefty: the only 10 pcs of available PC1066 128 MB Kingston RIMMs here retailed at around US$ 118 today per pc), get ready to add some more $$ for a good multi-fan chasis.

That chassis better not block the RIMMs with any 5.25" storage device bays or messy wires: the ventilation path must be clear.

Now further surprises: our own sources have also done some memory benchmarking on the upcoming Intel 7200 (Granite Bay) dual-channel PC2100 DDR chipset for the Pentium 4 and, guess what, its initial bandwidth results are not any better than the i850E with dual-channel PC1066. Of course, that PC2100 DDR memory is way cheaper. In the meantime, if you get some of the newer chipsets like SiS 648 or other with fast PC3200 (DDR400) support and some Samsung or Corsair PC3200 CL2 DIMMs to boot, you should have the second best performing P4 configuration possible, at quite a bit lower cost than PC1066 configurations.

Again, heat does become an issue for DDR as well at these speed: heat spreaders like those on Corsair XMS DIMMs do help, coupled with good memory area ventilation...

By the way, looks like most i850E mainboards will end up with the old south bridge (not the new ICH4) anyway. I'm curious to see how the upcoming SiS dual-channel DDR and RDRAM chipsets for the P4 will perform, especially once the new 2.66 GHz P4 grades are out in August. µ

See Nova's original review of Intel chipsets. Here.

CPU/Memory	P4-2.4 DDRRAM	P4-2.4 DDRRAM	P4-2.53 RDRAM	P4-2.4 RDRAM	P4-2.4 RDRAM	P4-2.4 RDRAM	P4-2.4 DDRRAM	P4-2.4 DDRRAM
FSB/Mem Type	533/PC800	400/PC3200	533/PC1066	533/PC1066	533/PC800	400/PC800	533/PC2100	533/PC2100
Chipset	SIS 645DX	SIS645DX	i850E	i850E	i850E	i850E	i845E	i845G
Motherboard	Asus P4S533	Asus P4S533	Intel D850EMV	Intel D850EMV	Intel D850EMV	Intel D850EMV	MSI 845 Max2	Intel D845GBV
3DMark2001SE
Default	11162	10813	11971	11808	11239	10968	11188	11204
1600x1200	7019	6963	7482	7424	7280	7208	7334	7265
PC Mark 2002
CPU score	5891	5917	6144	5816	5792	5768	5869	5866
Mem score	5666	5332	6060	5995	5257	5041	5101	5235
SYSmark2002
Internet	328	324	339	329	309	301	300	302
Office	167	166	165	161	150	150	148	149
Sandra
CPU Dhrystone	4455	4646	4871	4623	4722	4603	4671	4611
SSE2Whetstone	2949	2975	3131	2965	2923	2928	2959	2945
Multimedia Int	9540	9628	9997	9472	9489	9496	9570	9523
Multimedia FP	11613	11735	12179	11553	11591	11584	11671	11615
Memory INT	2937	2842	3311	3272	2894	2802	2009	2022
Memory FP	2921	2833	3298	3271	2896	2803	2008	2023