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.