Advantages Of Using Sxdram; When To Reserve Sxdram; Calculating The Amount Of Sxdram To Reserve - Sun Microsystems SPARCstation 10SX System Configuration Manual

Advantages of Using SXDRAM

As a configuration option, you can reserve SXDRAM. When SXDRAM is reserved,
the SX has additional optimizations available to it when accessing SXDRAM, and
operations on SXDRAM execute more quickly. The reserved memory, however, is
then not available for use by other applications. For example, on a 48-megabyte
system, allocating 16 megabytes of SXDRAM means that the system will in effect run
as a 32-megabyte system.

When to Reserve SXDRAM

Caution – The memory reserved for SXDRAM will not be available for system use.
When reserving SXDRAM, consider the amount of memory left for system use.
Ensure that there is sufficient memory left for system use that system performance is
not adversely affected.
Reserving SXDRAM can improve the performance of an application. The default
configuration is to use no SXDRAM.Typically, 4 MBytes must be reserved when Z-
buffering is used or when double-buffering is used alone. 8 MBytes of SXDRAM
must be reserved if both Z-buffering and double-buffering are used.
For image rotation operations, the amount of SXDRAM that must be reserved
should be the same as the size of the image, rounded up to the nearest integer
multiple of 1 MByte. For example, a 1200 x 1200 image with four 8-bit channels per
pixel will fit in 5.493 MBytes, requiring 6 MBytes of SXDRAM.
Calculating the Amount of SXDRAM to
Reserve
To calculate the amount of SXDRAM to reserve, add up the individual requirements
and round up to the next multiple of 1 MByte.
4 Platform Notes: SPARCstation 10SX and SPARCstation 20 System Configuration Guide • February 2000