More On Corsair's Low Latency DDR2-1000 Memory
This is a pair of Corsair CM2X512-8000UL modules. It is also available as a matched pair like that in our review, Corsair TWIN2X1024-8000UL.
Voltage Requirements For High Speed, Low Latency Operation
A close up of the specs that detail the model number, capacity, speed and recommended memory timings. We weren't able to find out what memory chips were used because the heat spreader was thermally bonded to the chips and if taken out, you'll have to find your own means to secure them back. That's not something we are going to risk with a rare memory set.
While we know some vendors have DDR2-1000 class memory modules that have been rated to work within 1.9 volts, which isn't asking much more than DDR2's recommended 1.8 volts operation, ultra low latency ones like Corsair's new TWIN2X1024-8000UL require much more input. When we identified the part numbers of the memory modules using CPU-Z and Sisoft Sandra, both programs acknowledged the RAM model correctly, but indicate a maximum clock frequency, bandwidth and the various timing parameters that actually adhere to Corsair's standard DDR2-800 modules (give and take some differences in Tras timings).
Just as we mentioned, CPU-Z identifies our RAM module correctly, but the RAM specs itself are more indicative of those found in DDR2-800 than this being a native DDR2-1000 part. Nothing out of the ordinary in the world of memory, but we are just providing more information for our readers.
Based on our findings, the TWIN2X1024-8000UL series (for now) are probably carefully handpicked DDR2-800 class modules that have been thoroughly validated by Corsair for much higher frequency operation and at aggressive timings. As such, we are not surprised that Corsair recommended 2.2V
for stable operation.
CPU, BIOS & Other Platform Requirements
Finding motherboards that are able to supply a VDIMM of 2.2 volts is just part of the equation to get the Corsair TWIN2X1024-8000UL up and running. The second most pertinent feature is the availability of suitable FSB:Memory ratios
in the BIOS, without which, you can never make full use of this expensive memory. Thirdly, if you would like to run DDR2-1000 without overclocking, you'll need to use a Pentium 4 Extreme Edition processor operating with a 1066MHz processor side bus
(in other words, equivalent to a 266MHz FSB).
At the point of publication, we know of only two Intel 955X motherboards that have an appropriate multiplier option, allowing you to use DDR2-1000 memory frequency without overclocking your Extreme Edition CPU and front side bus. These are the ASUS P5WD2 Premium and the Gigabyte GA-8I955X Royal motherboards, both of which we've reviewed recently. However the catch is that we couldnt get those options working at the point of testing since the ASUS board only offered that option in a newer BIOS that wasn't made available yet. Gigabyte's board on the other hand had this option, but it simply didn't work out for us. At 266MHz FSB, the Gigabyte board had 4x multiplier option, which is equivalent to DDR2-1066 operation. That however, was too much for our Corsair modules to cope no matter how high a voltage applied and how relaxed the latencies were set. Though Corsair's press release has mentioned of successful overclocking to DDR2-1066, whether one can achieve it is a question of the batch/yield quality of the memory chips on your module and the motherboard model and BIOS version paired. As always, overclocking is a game of trial and error and in our case, we couldn't achieve that.
Upping The FSB To 300MHz
Since we could not get DDR2-1000 operable with just the FSB:Memory ratio options, we had no choice but to resort to overclocking. In any case, this should be the more ideal scenario since these high speed memory modules were made to help overclockers hit high FSB frequencies and bridge up the wide discrepancy between the FSB and memory clock speeds (which ultimately results in better performance). The ASUS P5WD2 Premium motherboard was initially chosen to see if it could handle high FSB and memory clock speeds, since it is currently our record holder for the highest stable FSB achieved in our LGA775 motherboard reviews. During our overclocking runs in motherboard reviews, we stress the motherboard FSB handling only by keeping all other variables in check. This time however, we require both CPU and memory clock speeds to be run beyond their defaults. With the highest available memory frequency multiplier of 3.33x, we needed a 300MHz FSB using a 3.46GHz Extreme Edition processor (engineering sample using 12x multiplier) to achieve DDR2-1000. The ASUS P5WD2 Premium unfortunately didn't meet our mark and wasn't stable even at 290MHz FSB. Your own mileage may vary, but this was all we could coax out from the board we had.
We then tasked the Gigabyte GA-8I955X Royal motherboard with a similar array of settings, but pumped up the VDIMM to 2.3V and Voila! The system was found to be stable on all accounts, including the ultra low latency timings of 5-4-4-9. We had to bump the voltage up to 2.3V as for some odd reason, 2.2V was found to be quirky at exactly the 300MHz FSB mark. Apart from that, all was smooth and we were able to run a full suite of tests. We had the luxury of getting away with a stable system thanks to exhaustive overclocking and voltage tweaks found on the Gigabyte GA-8I955X Royal motherboard, if not for which this review might have never taken off.