Archive XMS Settings Here!
XMS Qualification and Testing Updated 6-1-2007
Corsair has developed a methodology in-house for developing, qualifying, and testing memory for use in over clocking applications. Some common questions about this process are answered below, and details are given for testing for specific XMS product families.
Q: What does XMS mean, and what is the idea behind it?
A: We have taken to heart a few facts that over clockers have known for years:
1) Many integrated circuits are capable of operating much faster than their specified speed
2) Standards organizations by their very nature have a difficult time keeping up with market changes.
XMS, or eXtreme Memory Speed, is the process that Corsair uses to take ICs rated at one speed and verify/guarantee their operation at another speed. Since specifications have not been generated to accurately specify operating parameters, Corsair gives these parts an XMS rating. For example, since PC2400 does not exist according to any valid standards institution, Corsair parts are called XMS2400.
Q: How do you verify operation at the XMS speed?
A: In a nutshell, through extensive evaluation in our lab. In order to offer an XMS module, a RAM must be found which can run with adequate stability in multiple platforms at the XMS-rated speed. Testing is done using both Corsairs’ stress-testing fixture, as well as by running common benchmarks, applications programs, operating systems, and games. Parts are evaluated over voltage and temperature extremes to monitor stability. No XMS part is released until all criteria are met.
Q: How do you guarantee operation at the XMS speed?
A: XMS parts are a speed screen of Corsair's standard parts. They are 100% tested at the XMS-rated speed; parts that fall out of this test are tested at the standard rated speed. For example, XMS2400 modules are 100% tested at 300 MHz. Parts that do not meet this speed grade are then tested at PC2100. Specific testing parameters for various XMS products are given below.
Q: How do you program the SPD of XMS parts?
A: Programming the SPD of our XMS parts is a bit problematic. The industry-standard specifications for the SPD values of XMS parts are often not yet defined by JEDEC (the appropriate standards organization) when the parts are introduced. In order to maintain compatibility with the multitudes of motherboards and BIOS revisions out there, the SPD values are programmed at the fastest available parameters defined by JEDEC. The SPD values are defined in the matrix below. Note, though, that in ALL CASES the Corsair part number (which contains the XMS speed grade) is programmed into the SPD as well.
XMS Specification_____SPD Values
XMS2700C2________JEDEC PC2700 values
XMS2700LL________Custom values
XMS3000__________JEDEC PC2700 values
XMS3200__________JEDEC PC3200 values
XMS3200C2________JEDEC PC3200 values
XMS3200LL________Custom values
XMS3200XL________Custom values
XMS3500LLPro______Custom values
XMS3500C2________JEDEC PC3200 values
XMS3700__________Custom values for PC3700*
XMS4000__________Custom values for PC3700*
XMS4400__________Custom values for PC3700*
XMS4400C25_______Custom values for PC3700*
* We do not expect PC3700 to ever be a ratified JEDEC specification; the values entered are based on what we would expect them to be.
Q: My XMS module does not work at the rated speed in my system. Why not?
A: There are many reasons why this can happen. Let me outline a few of them:
1) There are lots of motherboards out there, and we can only realistically evaluate/qualify a handful. You may have a motherboard that simply does not overclock well.
2) There is interaction between specific RAM manufacturers and specific motherboard manufacturers. Thus, for example, while EPoX boards might work best with RAM vendor A, Soyo boards might work better with RAM vendor B. Corsair strives to find the RAM that works most universally.
3) Other system components may not be overclockable. This may include the processor, chip set, PCI bus, IDE channel, etc.
4) The demands of today’s high end graphics cards and GHz processors the quality of your power supply has become increasingly important. Make sure you power supply make and model is approved by your motherboard manufacturer and/or your CPU manufacturer.
There are many sites on the web which can give you more reasons, tell you which boards are best for overclocking. To get an idea, go to your favorite search engine and search for "overclocking guide".
Q: I do not see the specific part that I have IE: XMS3200LLPT, why not? And what is the idea behind a slightly different part#?
A: The PT at the end of the part# in this case CMX512-3200LLPT indicates the color of the heat spreader, and would be a cosmetic change! This has no bearing on the memory or settings only the color.
*Important Note* Unless stated otherwise, all testing is done with only one module at a time.
Testing parameters for XMS2700 CAS 2:
CMX512-2700C2 Data Sheet
CMX256A-2700C2 Data Sheet
Motherboard make and model: EPoX EP-8K3A and/or Asus P4S533 and/or EPoX EP-8K5A
DRAM Timing (overrides SPD values): Manual
System Performance: Normal
SDRAM Bank cycle time (or tRAS): 6
SDRAM Bank Interleave: 4
SDRAM Row Precharge (tRP): 3
SDRAM RAS-to-CAS Delay (tRCD): 3
SDRAM CAS Latency: 2
Command Rate: 1T
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS2700LL:
CMX512-2700LL Data Sheet
CMX256A-2700LL Data Sheet
Motherboard make and model: Asus A7N8X.
All settings by MB default resulting in:
Memory Voltage: 2.7/2.75 Volts
Resulting Frequency: 166MHz
SDRAM CAS Latency: 2T
SDRAM RAS to CAS Delay (tRCD): 2T
SDRAM Row Precharge (tRP): 2T
SDRAM Active to Precharge Delay (tRAS): 5T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for TWINX2700LL:
TWINX1024-2700LL Data Sheet
TWINX512-2700LL Data Sheet
Motherboard make and model: Asus A7N8X.
Each pair is tested together using SPD values in an A7N8X with default settings resulting in:
Memory Voltage: 2.7/2.75 Volts
Resulting Frequency: 166MHz
SDRAM CAS Latency: 2T
SDRAM RAS to CAS Delay (tRCD): 2T
SDRAM Row Precharge (tRP): 2T
SDRAM Active to Precharge Delay (tRAS): 5T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS3000 CAS 2:
CMX512-3000C2 Data Sheet
CMX256A-3000C2 Data Sheet
Motherboard make and model: EPoX EP-8K3A and/or Asus P4S533 and/or EPoX EP-8K5A
Memory Voltage: 2.7/2.75 Volts
DRAM Clock: 187.5 MHz
DRAM Timing (overrides SPD values): Manual
System Performance: Normal
SDRAM Bank cycle time (or tRAS): 6
SDRAM Bank Interleave: 4
SDRAM Row Precharge (tRP): 3
SDRAM RAS-to-CAS Delay (tRCD): 3
SDRAM CAS Latency: 2
Command Rate: 1T
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS3200:
CMX512-3200 Data Sheet
CMX256A-3200 Data Sheet
Motherboard make and model: Asus P4C800/-E and/or DFI INFINITY I865/I875 and/or Asus A7N8X and/or ABIT IC7 Max3.
DRAM Clock: 200 MHz
DRAM Timing (overrides SPD values): Manual
System Performance: Normal
Memory Voltage: 2.7 Volts
SDRAM Bank cycle time (or tRAS): 8
SDRAM Bank Interleave: 4
SDRAM Row Precharge (tRP): 3
SDRAM RAS-to-CAS Delay (tRCD): 3
SDRAM CAS Latency: 3
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS3200C2:
CMX512-3200C2 Data Sheet
CMX256A-3200C2 Data Sheet
Motherboard make and model: EPoX EP-8K3A and/or Asus P4S533 and/or EPoX EP-8K5A, and/or Asus A7N8X.
DRAM Clock: 200 MHz
Memory Voltage: 2.7/2.75 Volts
DRAM Timing (overrides SPD values): Manual
System Performance: Normal
SDRAM Bank cycle time (or tRAS): 6
SDRAM Bank Interleave: 4
SDRAM Row Precharge (tRP): 3
SDRAM RAS-to-CAS Delay (tRCD): 3
SDRAM CAS Latency: 2
Command Rate: 1T
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for TWINX3200C2:
TWINX1024-3200C2 Data Sheet
TWINX512-3200C2 Data Sheet
Motherboard make and model: Asus A7N8X and/or Asus P4C800/-E and/or Abit IC7.
Each pair is tested and packaged together using the following settings:
Memory Voltage: 2.7/2.75 Volts
DRAM Clock: 200 MHz
SDRAM CAS Latency: 2T
SDRAM RAS to CAS Delay (tRCD): 3T
SDRAM Row Precharge (tRP): 3T
SDRAM Active to Precharge Delay (tRAS): 6T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS3200LL:
CMX512-3200LL Data Sheet
CMX256A-3200LL Data Sheet
Motherboard make and model: Asus A7N8X, and/or Abit KD7, and/or Asus P4C800/-E and/or DFI INFINITY I865/I875 and/or ABIT IC7 Max3.
All settings by MB default resulting in:
Memory Voltage: 2.7/2.75 Volts
DRAM Clock: 200 MHz
SDRAM CAS Latency: 2T
SDRAM RAS to CAS Delay (tRCD): 3T
SDRAM Row Precharge (tRP): 2T
SDRAM Active to Precharge Delay (tRAS): 6T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for TWINX3200LL:
TWINX1024-3200LL Data Sheet
TWINX512-3200LL Data Sheet
Motherboard make and model: Asus A7N8X, and/or Abit KD7, and/or Asus P4C800/-E and/or DFI INFINITY I865/I875 and/or ABIT IC7 Max3.
Each pair is tested together using SPD values with default settings resulting in:
Memory Voltage: 2.7/2.75 Volts
DRAM Clock: 200 MHz
SDRAM CAS Latency: 2T
SDRAM RAS to CAS Delay (tRCD): 3T
SDRAM Row Precharge (tRP): 2T
SDRAM Active to Precharge Delay (tRAS): 6T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS3200XL:
CMX512-3200XL Data Sheet
Motherboard make and model: Asus P4C800/-E and /or Asus A7N8X
DRAM Clock: 200 MHz
SDRAM VDIMM: 2.75
SDRAM CAS Latency: 2T
SDRAM RAS to CAS Delay (tRCD): 2T
SDRAM Row Precharge (tRP): 2T
SDRAM Active to Precharge Delay (tRAS): 5T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for TWINX3200XL:
TWINX1024-3200XL Data Sheet
Motherboard make and model: Asus P4C800/-E and/or Asus A7N8X
Each pair is tested and packaged together using the following settings:
DRAM Clock: 200 MHz
SDRAM VDIMM: 2.75
SDRAM CAS Latency: 2T
SDRAM RAS to CAS Delay (tRCD): 2T
SDRAM Row Precharge (tRP): 2T
SDRAM Active to Precharge Delay (tRAS): 5T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS3500 CAS 2:
CMX512-3500C2 Data Sheet
CMX256A-3500C2 Data Sheet
Motherboard make and model: Abit KD7 and/or Asus A7N8X
Memory Voltage: 2.7/2.75 Volts
CPU Speed: Manual
CPU External Frequency: 145MHz
CPU to Memory FSB ratio: 4:6
SDRAM Configuration: Manual
SDRAM CAS Latency: 2T
SDRAM RAS to CAS Delay (tRCD): 3T
SDRAM Row Precharge (tRP): 3T
SDRAM Active to Precharge Delay (tRAS): 7T
SDRAM Command Control: 1T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for TWINX3500LLPro:
TWINX2048-3500LLPro Data Sheet
Motherboard make and model: Asus A8N-SLI Premium
Each pair is tested and packaged together using the following settings:
CPU External Frequency: Manually set to 217MHz
Memory Voltage: 2.7/2.75 Volts
DRAM Clock: Manually set to 1:1 or 400MHz
SDRAM CAS Latency: 2.0T
SDRAM RAS to CAS Delay (tRCD): 3T
SDRAM Row Precharge (tRP): 2T
SDRAM Active to Precharge Delay (tRAS): 6T
SDRAM Bank Interleave: 4 Bank
SDRAM VDIMM: 2.75
Command Rate 1T
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS3700:
CMX512-3700 Data Sheet
CMX256A-3700 Data Sheet
Motherboard make and model: Asus P4C800/-E and/or Abit IC7/-G.
CPU External Frequency: 233MHz
Memory Voltage: 2.7/2.75 Volts
DRAM Clock: Manually set to 1:1 or 400MHz
SDRAM CAS Latency: 3T
SDRAM RAS to CAS Delay (tRCD): 4T
SDRAM Row Precharge (tRP): 4T
SDRAM Active to Precharge Delay (tRAS): 8T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for TWINX3700:
TWINX1024-3700 Data Sheet
TWINX512-3700 Data Sheet
Motherboard make and model: Asus P4C800/-E and/or Abit IC7/-G.
Each pair is tested and packaged together using the following settings:
CPU External Frequency: Manually set to 233MHz
DRAM Clock: Manually set to 1:1 or 400MHz
Memory Voltage: 2.7/2.75 Volts
SDRAM CAS Latency: 3T
SDRAM RAS to CAS Delay (tRCD): 4T
SDRAM Row Precharge (tRP): 4T
SDRAM Active to Precharge Delay (tRAS): 8T
SDRAM Bank Interleave: 4 Bank
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS4000:
CMX512-4000 Data Sheet
CMX256A-4000 Data Sheet
Motherboard make and model: Asus P4C800/-E and/or Abit IC7/-G.
CPU External Frequency: 250MHz
DRAM Clock: Manually set to 1:1 or 400MHz
SDRAM CAS Latency: 3T
SDRAM RAS to CAS Delay (tRCD): 4T
SDRAM Row Precharge (tRP): 4T
SDRAM Active to Precharge Delay (tRAS): 8T
SDRAM Bank Interleave: 4 Bank
SDRAM VDIMM: 2.75
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for TWINX4000:
TWINX1024-4000 Data Sheet
TWINX512-4000 Data Sheet
Motherboard make and model: Asus A7N8X and/or Asus P4C800/-E and/or Abit IC7/-G.
Each pair is tested and packaged together using the following settings:
CPU External Frequency: Manually set to 250MHz
DRAM Clock: Manually set to 1:1 or 400MHz
SDRAM CAS Latency: 3T
SDRAM RAS to CAS Delay (tRCD): 4T
SDRAM Row Precharge (tRP): 4T
SDRAM Active to Precharge Delay (tRAS): 8T
SDRAM Bank Interleave: 4 Bank
SDRAM VDIMM: 2.75
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for XMS4400:
CMX512-4400 Data Sheet
Motherboard make and model: Asus P4C800/-E
CPU External Frequency: Manually set to 275MHz
DRAM Clock: Manually set to 1:1 or 400MHz
SDRAM CAS Latency: 3T
SDRAM RAS to CAS Delay (tRCD): 4T
SDRAM Row Precharge (tRP): 4T
SDRAM Active to Precharge Delay (tRAS): 8T
SDRAM Bank Interleave: 4 Bank
SDRAM VDIMM: 2.75
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for TWINX4400:
TWINX1024-4400 Data Sheet
Motherboard make and model: Asus P4C800/-E
Each pair is tested and packaged together using the following settings:
CPU External Frequency: Manually set to 275MHz
DRAM Clock: Manually set to 1:1 or 400MHz
SDRAM CAS Latency: 3T
SDRAM RAS to CAS Delay (tRCD): 4T
SDRAM Row Precharge (tRP): 4T
SDRAM Active to Precharge Delay (tRAS): 8T
SDRAM Bank Interleave: 4 Bank
SDRAM VDIMM: 2.75
All other settings are motherboard defaults.
Maximum recommended VDIMM: 2.9
Testing parameters for TWINX4400C25:
TWINX1024-4400C25 Data Sheet
Motherboard make and model: Asus P4C800/-E
Each pair is tested and packaged together using the following settings:
CPU External Frequency: Manually set to 275MHz
DRAM Clock: Manually set to 1:1 or 400MHz
SDRAM CAS Latency: 2.5T
SDRAM RAS to CAS Delay (tRCD): 4T
SDRAM Row Precharge (tRP): 4T
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