Memory Module Analysis. Part 28:
Corsair DOMINATOR TWIN2X2048-10000C5DF
Memory Modules With EPP Support

We continue our analysis of the primary features of high-speed DDR2 memory modules today by taking a look at a new high-end product from the Corsair DOMINATOR series, the 2GB DDR2-1250 dual-channel kit. We will be analyzing performance of the modules using our RightMark Memory Analyzer tool, which is freely available on the web. These memory modules are the pinnacle of DDR2 technology, and also might have reached the final capacity of the DDR2 standard. This means that these modules very well might be the last DDR2-based modules in the Corsair Dominator series of products.

Manufacturer information

Module manufacturer: Corsair Memory

Chip manufacturer: unknown

Manufacturer's website: http://www.corsairmemory.com/corsair/dominator.html

Module exterior

The modules that are being reviewed look identical to the Corsair TWIN2X2048-9136C5D and TWIN2X2048-8888C4D entry level DOMINATOR products. One feature that distinguishes products in the DOMINATOR series is the new Dual-path Heat Xchange cooling technology. In essence, Corsair claims this cooling solution removes more heat in two ways; by using extruded aluminum heatsinks with “optimized” fins to increase airflow and dissipate more heat and by using a dedicated heatsink for the PCB itself.

These modules can be additionally cooled by the supplied DOMINATOR Airflow Fans system which creates direct airflow to modules for improved heat removal.

Module part number

Unfortunately, at the Corsair company website we were unable to find a part number guide for the DOMINATOR DDR2 series.

The TWIN2X2048-10000N5DF product sheet states that the kit consists of 2 x 1GB CM2X1024-10000N5D modules. The modules support Enhaned Performance Profiles (Serial Presence Detect extension), an open standard jointly created by Corsair and NVIDIA. EPP allows memory settings to be automatically optimized on motherboards that support EPP. It has been developed primarily to make overclocking easier.

Corsair guarantees that the modules will work at DDR2-1250 speeds with EPP timings of 5-5-5-18-2T and a rather «extreme» voltage of 2.4 V on motherboards based on the NVIDIA nForce 680i SLI EVGA chipset. At that voltage setting, by default the SPD sets memory speed to DDR2-800 mode at 5-5-5-18 timings.

SPD Data

General SPD standard specification:

• JEDEC Standard No. 21-C, 4.1.2 - SERIAL PRESENCE DETECT STANDARD, General Standard

DDR2 SPD standard specification:

• JEDEC Standard No. 21-C, 4.1.2.10 - Appendix X: Specific SPDs for DDR2 SDRAM (Revision 1.2)

Taking a look at the SPD chip on the modules, the part number of the SPD ROM of the modules under review today matches up to the number of the SPD chip on the previously reviewed CM2X1024-9136C5D and CM2X1024-8888C4D modules. The maximum performance that today's modules are designed for is a 2.5 ns cycle time (400 MHz frequency, DDR2-800). The first of the supported values is tCL = 5, while the complete timing scheme is 5-5-5-18, which agrees with what the manufacturer states in its brief documentation for the memory kit. Lower CAS# signal latency values (CL X-1 = 4) can be achieved using a non-standard clock signal period of 3.7 ns (typical for Corsair memory modules), which corresponds to a frequency of approximately 270 MHz. Most likely , this setting is meant for DDR2-533 mode with a 3.75 ns cycle time. An improper clock signal period value leads to non-integer values in the timing scheme, which can be written (rounded to one decimal place) as 4-3.4-3.4-12.2 and rounded up to integer values, as 4-4-4-13. As a matter of fact, DDR2-533 is obsolete in today's day and age, especially for such high-speed modules, so these values hardly bear any true significance. In our opinion, this setting should have been excluded from the SPD memory quite some time ago.

Although the manufacturer identification code along with the module part number is stated correctly, as is true with other Corsair modules, the SPD chip does not give details regarding the manufacturing date and serial number. In this case, they are filled with a value of FFh.

Now let us look at the most critical information in the «non-standard» part of the SPD, bytes 99-127 of the SPD memory which contains the EPP profiles.

EPP standard specification:

• DDR2 UDIMM Enhanced Performance Profiles, revision 01

The modules being examined support Enhanced Performance Profiles and contain information for two «extended» profiles. Of the two enhanced profiles, only the second one (Profile #1) is operative and is, naturally, marked as recommended by default. This profile has a cycle time of 1.60 ns, meaning it has a frequency of 625 MHz; a «DDR2-1250» rating. The timings of this profile can not be completely represented using integers and is written as 5-5-5-17.5, which, evidently, should be interpreted by motherboards supporting EPP as 5-5-5-18. Delays in address-command interface for this profile amount to 2T while the modules' power supply voltage is at 2.4 V. The minimum row cycle time (tRC), is a mere 15 cycles of external data bus, a rather small value which comes as a bit of a surprise, primarily because it turns out to be less than the tRASparameter, which is 17.5 (18) cycles of external data bus. It is possible that this in fact is a mistake that was made on the manufacturer's part when coding the EPP profile data.