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PCI/I-486SP3G
User's Manual
Upgrading System Memory
This section explains how to install more system memory. There
are instructions on how to configure and install memory and an
ex-
planation of the technical
specifications
required.
System DRAM is the main
source
of data for the CPU. Data re-
mains
stored
in DRAM as long as the
system
is turned on, and is lost
when you turn it off. The Level
2 cache
memory is Static RAM
(SRAM), which is faster than DRAM memory. When the CPU looks
for data, it first searches the
cache.
If
the information is not there, the
search continues in the DRAM. With this design, the CPU looks in
the fastest
source
of data first, which lets it operate as fast as possible.
The DRAM
subsystem
uses memory
chips
permanently mounted
on small circuit boards to form "SIMMs" (Single In-line Memory
Modules). The memory
chips
have a
speed
rating that is measured
in nanoseconds (ns). The PCI/I-486SP3G requires fast page mode
DRAM with a
speed of at
least
70ns.
This mainboard
can
use
72-pin SIMMs
in
six
sizes of lMB, 2MB,
4MB, 8MB, 16MB, and
32MB
(megabytes). Depending on the com-
bination of modules you use, you can install between 4MB and
128MB. The 32-bit modules used for this board come with memory
chips on either one or both
sides
of the module.
Upgrade Guide
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Configuring System Memory
If
you want to add system memory, you must use the configura-
tion options and
specifications
shown in this section.
Memory Combinations
You can configure the memory of the PCI/I-486SP3G in
a
vari-
ety of ways, using different combinations of SIMM modules. You
can
configure the mainboard's 4 SIMM
sockets
in 48 combinations using
lMB, 4MB, and 16MB SIMMs with chips on only one
side
of the
SIMM, and 2MB, 8MB, or 32MB SIMMs with chips on both
sides.
The chart on the next two pages shows the possible combinations.
Under "Type", SIMMs with chips on one
side
are listed as "Single";
those with chips on both
sides are
listed as "Double".
The only restrictions are:
• You must use 2 sockets at a time, in sequence, e.g. SIMMl
and SIMM 2, SIMM 3 and SIMM 4, or all four sockets at
once.
• Each pair of modules must be the same size and speed.
• Required Memory Specifications:
Module Size: lMB, 2MB, 4MB, 8MB, 16MB, or 32MB
DRAM Mode: Fast Page Mode
DRAM Speed: 70ns (or faster)
RAS access time [Trac]: 60ns
-
70ns
CAS access time [Tcac]: lOns - 25ns
Parity: Either parity or non-parity
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