random access memory/timing

In general, lower numbers are better (the only exception is the speed). RAM should work in a device as long as the device's required numbers are not lower than those for the RAM.

I think the format is:

• <tech>-<internal clock speed> <CAS>-<tRCD>-<tRP>-<tRAS>[-<CMD>]
  • example: PC3-10600S-09-10-F2
    • tech = PC3
    • speed = 10600 (S = ?)
    • CAS = 09
    • tRCD = 10
    • tRP = F2(?)

...but I haven't been able to confirm all of this.

Terms

• CAS = Column Address Strobe latency, aka CL
  • CASn or CLn means the memory controller must wait n clock cycles until data is delivered after a request is made
  • This is the time it takes between (a) the processor asking for some data from the memory and (b) receiving it.
• tRCD = RAS-to-CAS Delay = the time it takes between the activation of the line (RAS) and the column (CAS) where the data are stored in the matrix
• tRP = RAS Precharge = the time it takes between disabling the access to a line of data and the beginning of the access to another line of data
• tRAS = Active to Precharge Delay = how long the memory has to wait until the next access to the memory can be initiated
• CMD = Command Rate = the number of clock cycles it takes between the memory chip having been activated and when the first command may be sent to the memory
  • Sometimes this value is not shown.
  • It usually is T1 (1 clock cycle) or T2 (2 clock cycles).

Usually, you have two options: to configure your PC to use the memory standard timings, usually by setting memory configuration to “Auto” on the motherboard setup; or to manually configure your PC to use lower memory timings, which may increase the performance of your system. Notice that not all motherboards allow you to change the memory timings. Also, some motherboards may not be able to run at very low timings, and they may configure your memory module to run at a higher timing setting because of this.

Source

• 2011-05-17 Understanding RAM Timings

Reference

• Wikipedia: Memory timings