Corsair XMS TWINX2048-4000PT 2GB Dual Channel Kit

Written by John Chen    Tuesday, 13 December 2005 11:00
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Corsair XMS TWINX2048-4000PT 2GB Dual Channel Kit
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When the 2GB frenzy began, Corsair was one of the first companies to depend on for quality enthusiast memory.  Unlike their competitors, Corsair made their introduction with Infineon ICs.  When I first heard about their PC4400PRO, currently the fastest rated memory on the market, I thought it used Samsung UCCC ICs just like the rest of the other guys.  At the time, Samsung UCCC chips were the only chips that were capable of running high frequencies, albeit loose timings were required.  I was quite surprised to find the use of Infineon chips underneath.  Not only did Corsair use Infineon chips for their PC4400PRO part, they also used it for their PC3500LLPRO.  One part focused on high speeds while the other focused on tight timings.  Unfortunately like all high end enthusiast memory, those two parts also come with a hefty price tag.  Corsair's newest PC4000 part aims to fill in the gap, providing performance at a reasonable cost.


Corsair XMS PC4000PT

The PC4000PT comes in Corsair's standard clamshell package.  The memory does not come with fancy heatspreaders like the PRO series, but rather the simplest heatspreaders used throughout the past few years.  I personally prefer the black version of the heatspreaders because the paint job on the silver ones look terrible.  They scratch easily. 

The PC4000PT uses Samsung UCCC ICs and are loosely rated with timings of 3-4-4-8 at 250MHz, or DDR500.  The sample I received came with a date code of 534 on the memory chips.  Much like the infamous TCCD ICs, UCCC overclocking results do vary depending on the date codes.  We will see how well these overclock compared to the first generation 525 UCCCs.  I checked the specifications sheet over at Corsair's website and it did not mention anything about the rated voltage.  A quick glance over at Newegg showed a 2.75v requirement.  That looks to be about right for UCCC ICs.  I normally run them at 2.8v since the small increase does yield a better overclock.  Anything higher is all up in the air.  The PCB used for the PC4000PT appears to be the 808/815 solution from Brainpower.  Brainpower PCBs are becoming quite common now and enthusiasts favor them because of the better overclocking yields. 



Test System and Overclocking

Test System:

  • AMD Athlon 64 3700+ San Diego
  • DFI LANParty UT nF4 Ultra-D
  • 2 x 1GB Corsair XMS PC4000PT
  • ATI Radeon X800XT
  • Arctic Cooling Freezer 64
  • SilverStone ST65ZF
  • BIOS 623-3 and orange slots


Keep in mind that during overclocking, the latencies are as follows:  CAS-TRCD-TRP-TRAS

The CPU multiplier has been kept at 9x to prevent any CPU bottlenecks during the overclocking process.  My San Diego 3700+ has a good integrated memory controller and has been double checked to make sure that it is not a source of bottleneck.  The CPU has been tested and verified to be stable to at least 9x300HTT = 2.7GHz.  Thus, all benchmarks will be conducted with a 9x multiplier.

I began the initial testing to see the lowest timings the memory would allow.  Unlike TCCD that can withstand low latencies at low frequencies, the tightest timings these UCCC chips would allow was 2.5-3-3.  I set TRAS at 7 for the best balance of performance and stability.  I kept the timings of 2.5-3-3-7 and slowly began to increase the memory speed, keeping the ratio at 1:1 at all times.  Much to my surprise, the PC4000PT allowed up to 240MHz!  That is the highest I have seen from UCCC with timings of 2.5-3-3-7.  I loosened the TRCD to 4 and managed to gain another 5MHz increase to 245MHz.  Contrary to what many people believe, Samsung UCCC chips do not really have the characteristic of running TRP at 2, i.e. timings of 3-3-2.  Maybe one out of a big lot would achieve such a feat, but the majority of UCCCs respond better to loose timings all around.  Timings of 2.5-4-4-8 and 3-3-3-8 did not provide any help.  I had to loosen to 3-4-3-8 before the memory would budge.  3-4-3-8 is the optimal setting that UCCC ICs tend to like.  They scale quite high with those timings and run very stable without excessive voltage.  With just 2.8v, the PC4000PT pushed to its limits of 270MHz.  I tried looser timings of 3-4-4-8, increased voltage of 2.9v and 3.0v, and even tried lower voltages of 2.6v and 2.7v and nothing helped.  It looks like the memory has reached its peak.  As I mentioned earlier, the date codes on the UCCC ICs do matter.  My very first kit of UCCC based memory was the OCZ Gold PC4000.  Those came with date code 525 and hit a whopping 280MHz with 3-4-4-8.

Overclocking Results:

  • 200MHz  2.5-3-3-7  1T  2.8v
  • 240MHz  2.5-3-3-7  1T  2.8v
  • 245MHz  2.5-4-3-7  1T  2.8v
  • 270MHz  3.0-4-3-8  1T  2.8v


A series of memory intensive benchmarks will be run to test the performance of our sample. The other tests will be based on common benchmark programs, such as 3DMark and PCMark. Real life performance differences will be tested through current games, such as Far Cry and UT2004. Memory bandwidth benchmarks will be based off of SiSoft Sandra and Everest Home Edition. Super PI and PiFast will also be used to test memory performance, as the benchmark benefits largely from FSB increases.

SiSoft Sandra Memory Bandwidth

SiSoft Sandra is the most widely used memory bandwidth test.  It can tell you the increase in performance from just lowering the latency timings.

Everest Home Edition

Much like Sandra, Everest Home Edition tests the memory's ability to read and write data in large chunks.  The results show that the lower latencies seem to help just a little with performance.


3DMark is likely the overclocker's favorite benchmark.  Unlike 3DMark2003, which stresses mainly the video card, 3DMark2001SE tests all of the system's main components.  Increasing the CPU speed, memory speed, and video card speeds will result in higher results in the final score.



Results Continued

Far Cry

Since Far Cry is a game, the performance results will be very similar to 3dMark2001.  I ran the benchmark at 640x480, so the benchmark would not be too GPU-dependent.  The tests under 1024x768 and 1280x1024 are an approximation of what kind of frames you'll be getting.  While the results are similar to 3dMark2001 in performance, this benchmark will give more significant results, because Far Cry is a lot more demanding.

Unreal Tournament 2004

Unreal Tournament is another popular game engine to test overall system performance.  Here, we can see the same results as Far Cry and 3dMark2001.  Like Far Cry, UT2004 was also run at 640x480 to limit GPU dependency.  The other resolutions provide an approximation of actual game play performance.


PCMark is another benchmark created by Futuremark.  It tests the memory compression and decompression speeds in small to large chunks of data.

Super PI

Since the value of PI is an infinite value, Super PI is a speed test to find the digit you're looking for.  In this case, we chose the millionth digit.  Super PI benefits greatly from higher FSB, as well as low latencies.


PiFast is similar to Super PI.  The results can be greatly affected by a slight adjustment to the memory megahertz and latency.



Conclusion and Thoughts

Although Corsair was a bit late with their UCCC solution, they have done a good job.  The overclocking result is not as high as what I have seen with previous experiences, but that is not Corsair's fault.  Keep in mind that date codes on UCCC ICs do matter when it comes to overclocking results.  As of right now, the best date code is 525.  There might be better ones in the future, but who knows how long Samsung will take.  Good TCCD ICs went from 431/437 to 519.  There was a huge gap where TCCD was just decent and nothing exceptional.  Let's hope that Samsung is faster and better with their production line so companies like Corsair can release high clocking PC4000PT parts.

The targeted crowd of the PC4000PT is the gaming enthusiasts who cannot afford to shell out the big greens for top of the line stuff, but still want to run high end parts in their gaming system.  After all, games gain a good deal of performance increase when high end parts are used.   The price of 2GB memory has dropped significantly from the past few months and the PC4000PT has become a great choice.  The memory is very affordable at around $250 and overclocks nicely without requiring high voltage, making these modules very appealing.  Pairing these with a good clocking 10x multiplier CPU and you will start fragging with a good 2.6GHz-2.7GHz system. 


  • Affordable enthusiast 2GB solution
  • Overclocks very well with timings of 2.5-3-3
  • Less expensive than Infineon based modules
  • Has a good amount of overclocking headroom


  • Ugly silver heatspreaders (personal opinion here)

We would like to thank Corsair for providing us the sample.  If you have any questions or comments, feel free to hit us up in the forums. You can also check out more of our latest reviews on the front page.