(This document is part of the PC-Clone Unix Hardware Buyer's Guide. The Guide is maintained by Eric S. Raymond ; please email comments and corrections to him.)

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Memory

All current PC designs include a cacheing memory controller and some SRAM that combine to produce higher effective speeds. Be sure to read the `Cache Flow' section under performance tuning for more on how cache configuration affects your performance.

Current motherboards use PC100 SDRAM, which comes packaged on 168 pin DIMM modules. SDRAM is a large step forward in memory speed, at 10ns. SDRAM does not need to be installed in pairs. The key words you want to see on the spec sheet are:

SDRAM DIMM -- the physical module type
ECC -- error correcting memory, important for reliability; Unix makes more efficient use of hhardware and thus beats on your memory harder than Windows does.
PC100 -- this is the memory-module specification for current motherboards with a 100Mhz PCI bus.
16x72 -- if it says 16x64, the extra 8 bits per 64 needed for ECC are not present.

Also, avoid anything that says `ECC compatible memory'; this is the opposite of `memory with ECC'.

For more technical stuff on memory architectures, see The Ultimate Memory Guide maintained by Kingston Technologies.

Eric S. Raymond