Abit AX5 Instruction Booklet page 34

2-18
3. Maximum memory capacity 256M bytes supported by this
mainboard.
Computer ¡i
knowledge
CPUs ¡j
Pentium P54C . P55C, Cyrix 6x86 and AMD-K5/K6 are all 64
bit CPUs, but 72-pin SIMM modules are only 32-bit. That' s why
they have to be used in pairs, because the CPU will always be
only able to see 64 bits. This means that 72-pin SIMM modules
have to be installed in pairs. For instance, SIMM1 and SIMM2
must form a pair, and
another pair. Of course, the two members of a pair must be of
the same kind ¡i EDO or FP DRAM ¡j , and you cannot use
pairs from different "species".
But the AX5/TX5 support different "pairs" and use different type
of memory modules, notice:
168-pin DIMM modules are 64 bit, so you can use single
modules. On the AX5/PX5/TX5 mainboard, these modules can
support not only EDO and FP DRAM, but also Synchronous
DRAM memory configurations.
When you install DIMM modules on the mainboard, you don' t have to
setup anything, just be sure that you use 3.3V unbuffered 168-pin DIMM
modules, and insert them in the memory socket.
Relationships between memory modules and Pentium
l ¡i SIMM1 and SIMM2 ¡j must use the same
memory type,
SIMM4 ¡j .
l ¡i SIMM1 and SIMM2 ¡j use the same memory
type, and ¡i SIMM3 and
the same type, or a different type, in order to permit you
to obtain the best speed configuration for each "single"
pair, and to make the system work at its maximum
capacity. If one memory pair is slower, it will have no
influence on the pair whose speed is higher.
SIMM3 and SIMM4 must form
¡i
as well as
SIMM4 ¡j can use
Chapter 2
SIMM3 and