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3 System Board (P/Ns D3657-63001 and D3661-63001)
Devices on the Processor Local Bus
Main Memory
There are six main memory module sockets on the system board, enabling
up to 128 MB of main memory to be installed. The sockets are arranged in
three banks (A to C). Memory modules must be installed in pairs which are
the same size to ensure that all the memory is configured correctly.
Fast memory access, with the timing pattern 7-2-2-2, is achieved by
installing EDO RAM. The PC supports 60 ns EDO or 70 ns FPM DRAM.
The PL/PCI bridge chip (SB82437FX-66) provides the dedicated DRAM
memory address and data buses. It implements a page mode of operation,
allowing one or two pages to be open simultaneously.
The two data path unit chips (SB82438FX), controlled by the PL/PCI bridge
chip, implement a 64-bit data path (not interleaved) between the processor
local bus and main memory modules. They also provide a buffer, four 64-bit
words in depth, which can be used for writes from processor to main
memory, level-2 cache write-back cycles, and transfers from PCI to main
memory. It also provides a one-level posted write buffer for all processor
writes to the PCI bus memory.