The following constraints are described in terms of the SPARCstation 10SX, but the same concerns apply to the SPARCstation 20.
The first slot (slot 0) must always be configured with a DSIMM.
The minimum recommended amount of memory required for reasonable SPARCstation 10SX performance is 32 MByte. Thus, to be able to reserve SXDRAM, a system should be configured with more than 32 MBytes of DRAM. However, users can configure the minimum amount of memory that must be reserved for system use by using the -l option of the sxconfig (1M) command. The difference between the amount of DRAM installed on the system and the configured minimum limit (32 MBytes by default) is the maximum amount of memory that can be reserved for SXDRAM.
The amount of physically contiguous memory that should be reserved must be specified as an integer multiple of 1 MByte. Thus, the minimum amount that can be reserved is 1 MByte.