User guide

11
Acorn Risc PC Release note
Purchasing additional memory modules
The Acorn Risc PC uses standard Single In-line Memory Modules (
SIMMs). There are two SIMM sockets; each socket can hold an
industry-standard 32-bit wide 72-way SIMM with gold or tin solder
contact pads.
If you wish to add more memory to your computer, you can obtain
SIMMs from reputable memory suppliers. The following table describes
the criteria which SIMMs must adhere to. You should read these
carefully if you are planning to purchase 'off the shelf' modules from a
supplier who does not specifically stock parts for the Acorn Risc PC.
Suitable SIMMs may be identified by the following memory sizes:
2 MBytes 512K x 32
4 MBytes 1M x 32 All SIMM modules
8 MBytes 2M x 32 must be rated 70ns or
16 MBytes 4M x 32 faster.
32 MBytes 8M x 32
*64 MBytes 16M x 32
*128 MBytes 32M x 32
* When available. These sizes of SIMMs were not available during
the Acorn Risc PC's development. Acorn is unable to guarantee
compatibility of any SIMMs of these sizes with the Acorn Risc PC.
All SIMM modules must be rated 70ns or faster. 50ns or 60ns is
acceptable, but 80ns is not.
As a guide, memory modules with more than 16 memory 'chips' (ie.
8 on each side) will be unsuitable as these modules will put too
great a load on the computer. The exact limits are given overleaf
under 'loading data' and you should draw these figures to the attention
of your supplier if in any doubt.
If you are unsure about what to purchase, we strongly suggest you
contact your local Acorn dealer who will advise you appropriately.
In the event that your dealer is not sure which SIMM to sell you,
show him the following information: