CM654S128-133C2 - PC133 128 Mb CAS2 memory
Truly High performance PC133 memory modules

Manufacturer - Corsair
www.corsairmicro.com
Wednesday, August 23, 2000 - Hilbert Hagedoorn

Corsair has outdone themselves once again, recently we received a small sample of their CAS2 PC133 DIMM module. Known for their reputation of high quality DRAM's and PCB's they continued their line of everlasting goodness with this CM654S128-133C2 (128MB, PC133, 16Mx64, unbuffered, CAS2, 8Mx8 DRAMs) module. CAS2 PC133 memory modules are recommended for newer systems that run a 133 MHz memory bus speed since most 'normal' modules will not work properly at CAS2 with such a bus speed.

Features:

Industry standard PC100/PC133 DIMM Format

Two mechanical configurations Standard PC100/PC133: 1.350 inch maximum height Low Profile: 1.125 inches maximum height, for 1U rackmount systems

Cost-effective density using 64 MBit and/or 128 MBit SDRAMs

High Performance unbuffered synchronous DRAM all inputs synchronized to system clock

Single 3.3V ± 0.3V power supply

Serial Presence Detect (SPD) EEPROM provides automatic memory configuration

Series termination on clock and data lines

LVTTL-compatible inputs and outputs

Two component configurations Standard: Built using sixteen 8M x 8 SDRAMS, 4K refresh “A” Version: Built using eight 16M x 8 SDRAMS, 4K refresh

Pin-compatible with all PC100 and PC133 modules

CAS2 Latency, what does it mean? - A question that I hear a lot is what is the essential difference between CAS3 and CAS2. Simple answer, the effect is raw speed ! To explain CAS you really how to get an impression on how memory works, although I'm not a memory module expert I'll give it a try. You may have some PC133 memory already, or you might even be running some PC100 memory overclocked to 133MHz. Is this Corsair RAM different? Hmm yes, it is!

If we talk about SDRAM timing we mean two things. The first one that we encounter is the memory bus speed, MHz. In most cases this is equal to the  CPU's Front-Side-Bus (FSB) speed, except for newer VIA mainboards who can run an FSB of 100 and it's memory at 133 MHz.

The second item we need to set (and now we're getting closer to Corsairs CAS2 memory) is of course the CAS latency in either a setting of  3 or 2. (CAS = Column Access Strobe) It handles to the part of the memory access cycle. To put it into geek words the CAS is a delay as  the SDRAM subsystem accesses the correct part of the memory. In other words, the lower the number (CAS2), the faster the memory access cycle will get. In return, the memory bandwidth will increase and thus we'll notice an increase in performance. The higher the CAS (3) the slower memory access will be. The majority of memory modules these days is CAS3 PC133. PC133-CAS3 is therefore guaranteed to work a FSB of 133 MHz but with a CAS Delay of 3. The reason why the Corsair is so special is that it's guaranteed by the manufacturer to run at 133MHz at CAS2. This is truly good news for overclockers, tweakers and people who like to push the most out of their system since it'll bring us the option going back to CAS3 if we're pushing the RAM to much higher frequencies.

Time for some benchmarks.

We ran a couple of tests with SiSoft's Sandra Professional. We choose to benchmark the module in CAS2 and CAS3 and made a comparison towards PC100 DIMM's. As you can see in the table, CAS2 PC133 rocks all tests but the findings are pretty close. If we look at games for example the framerate could be boosted with about 3% maybe 4% at it's best. If we would push the CPU's FSB higher than 133 MHz then this memory is flexible enough to pickup that FSB speed and get some real but mostly more performance out of it.

Concluding - Corsair memory modules are basically one of the best you can choose from, Will CAS2 benefit you more compared to CAS3 memory ? Well, if you look at our findings then it will benefit a little, and hey all small bits help right ? Furthermore you need to bare in mind that future PC's will have a higher FSB setting which this module will easily be compatible with. 

A recent test from Anandtech (read here) shows that Corsair's memory can go up to a 146 MHz bus speed in both CAS2 and CAS3, that's really amazing. 
What can I say more than that the CM654S128-133C2 is a really good module to own in your either your VIA or Intel based mainboard. If you want maximum speed and stability then this is the module you should choose. 
We are going to reward the CM654S128-133C2 DIMM module with our editor's choice award, which actually is the first one we give away this year.

The CM654S128-133C2 is already selling for about $205 which is a very competitive price. You can check out the best prices by clicking here.

Copyright 1999 - All rights reserved Hilbert Hagedoorn