Memory configurers recommend more expensive memory with cl=2.5 and 6 layer for my fic vi13l motherboard. Will the cheaper memory with cl=3 and 4 layer still work? Why? Thanks! (mem is ddr pc2100 266mhz)(motherboard fic V113L)

It may, it may not, it may work a bit, and only read half the chip. Have a look here: http://www.fic.com.tw/support/motherboard/motherboard.aspx?model_id=109 for the MB manual, if you dont want to spend the time reading through it, then play it safe and get the better ram, *Note* that even if the CL3 ram works it may be less stable, and will not perform as well.

The CLx setting tells how long the ram needs to pause between it's read/write cycles. The higher the CL the more cycles it needs and the slower it is. The difference isn't really that big but if you run CL3 or CL4 run with the CL2,5 CAS settings it may not work properly. Normally the slower ram should also work but if the board is build to run with faster ram there maybe a problem.

One more thing, a 6 layer PCB will have a decreased amount of noise along the circuit vs. a 4 layer PCB. A 6 layer PCB is recommended.

Thanks everyone. Your answers were a big help!