Service manual

System Overview 1-23
Memory Variants
Each memory option consists of two identical modules. Each 4100 drawer supports
up to four memory options, for a total of 4 Gbytes of memory: 4000 drawers support
half that. Memory modules are used only in pairs and are available in 128 Mbyte,
512 Mbyte, and 1 Gbyte sizes. The 128-Mbyte option is synchronous memory,
while the larger sizes are asynchronous memory (EDO).
DRAM
Option Size Module Type Number Size
MS320-CA 128 MB B3020-CA Synch. 36 4 MB x 4
MS330-EA 512 MB B3030-EA Asynch. (EDO) 144 4 MB x 4
MS330-FA 1 GB B3030-FA Asynch. (EDO) 72 16 MB x 4
MS330-GA 2 GB B3030-GA Asynch. (EDO) 144 16 MB x 4
Memory Operation
Memory modules are used only in pairs; each module provides half the data, or 64
bits plus 8 ECC bits, of the octaword (16 byte) transferred on the system bus.
Modules are placed in slots designated MEMxL and MEMxH.
NOTE: Modules in slots MEMxL do not drive the lower 8 bytes, and modules in
slots MEMxH do not drive the higher 8 bytes of the 16 byte transfer.
Unless otherwise programmed, memory drives the system bus in bursts. Upon each
memory fetch, data is transferred in 4 consecutive cycles transferring 64 bytes.
There are situations, however, when memories made with EDO DRAMs cannot
provide data fast enough to complete the system bus transactions. When these
situations arise, EDO type memories assert a signal that causes the system bus to
stall for one (occasionally more) clock tick. When memory completes such an
operation, it releases the system bus.
Memory Configuration Rules
In a system, memories of different sizes and types are permitted, but:
• Memory modules are installed and used in pairs. Both modules in a memory
pair must be of the same size and type.
• The largest memory pair must be in slots MEM 0L and MEM 0H.
• Other memory pairs must be the same size or smaller than the first memory pair.
• Memory pairs must be installed in consecutive slots.