Sections Offered In This Course...

- Qualification and Testing	- What does XMS mean	- How do you verify
- How do you guarantee	- How do you program	- Testing parameters

XMS Qualification and Testing
Corsair has developed a methodology in-house for developing, qualifying, and testing memory for use in overclocking applications. Some common questions about this process are answered below, and details are given for testing for specific XMS product families.

What does XMS mean, and what is the idea behind it?
We have taken to heart a few facts that overclockers have known for years: [1] that many integrated circuits are capable of operating much faster than their specified speed, and [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.

How do you verify operation at the XMS speed?
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 Corsair's 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.

How do you guarantee operation at the XMS speed?
XMS parts are a speedscreen 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.

How do you program the SPD of XMS parts?
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 programed 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.

• 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.
  
• 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.
  
• Other system components may not be overclockable. This may include the processor, chip set, PCI bus, IDE channel, etc.

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".

Testing parameters for XMS150:
- Motherboard make and model: Asus CUSL-2
- DRAM Clock: 150 MHz
- RAS Precharge: 2
- RAS-to-CAS Delay: 2
- CAS Latency: 2
- Memory Voltage: motherboard default

Testing parameters for XMS2400:
- Motherboard make and model: EPoX 3VHA and/or EPoX 8KHA+
- DRAM Clock: 150 MHz
- DRAM Timing (overrides SPD values): Manual
- System Performance: Normal
- Bank cycle time (or tRAS): 6
- RAS Precharge: 2
- RAS-to-CAS Delay: 2
- CAS Latency: 2
- Command Rate: 1T
- Memory Voltage: motherboard default*

Testing parameters for XMS2700 CAS 2:
- 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
- Bank cycle time (or tRAS): 6
- Bank Interleave: 4
- RAS Precharge (tRP): 3
- RAS-to-CAS Delay (tRCD): 3
- CAS Latency: 2
- Command Rate: 1T
- Memory Voltage: motherboard default*

Testing parameters for XMS3000 CAS 2:
- Motherboard make and model: EPoX EP-8K3A and/or Asus P4S533 and/or EPoX EP-8K5A
DRAM Clock: 187.5 MHz
DRAM Timing (overrides SPD values): Manual
System Performance: Normal
Bank cycle time (or tRAS): 6
Bank Interleave: 4
RAS Precharge (tRP): 3
RAS-to-CAS Delay (tRCD): 3
CAS Latency: 2
Command Rate: 1T
Memory Voltage: motherboard default*

Testing parameters for XMS3200 CAS 2.5:
- Motherboard make and model: EPoX EP-8K3A and/or Asus P4S533 and/or EPoX EP-8K5A
- DRAM Clock: 200 MHz
- DRAM Timing (overrides SPD values): Manual
- System Performance: Normal
- Bank cycle time (or tRAS): 6
- Bank Interleave: 4
- RAS Precharge (tRP): 3
- RAS-to-CAS Delay (tRCD): 3
- CAS Latency: 2.5
- Command Rate: 2T
- Memory Voltage: motherboard default*

Testing parameters for XMS3200 CAS 2:
- Motherboard make and model: EPoX EP-8K3A and/or Asus P4S533 and/or EPoX EP-8K5A
- DRAM Clock: 200 MHz
- DRAM Timing (overrides SPD values): Manual
- System Performance: Normal
- Bank cycle time (or tRAS): 6
- Bank Interleave: 4
- RAS Precharge (tRP): 3
- RAS-to-CAS Delay (tRCD): 3
- CAS Latency: 2
- Command Rate: 1T
- Memory Voltage: motherboard default*