Octek Hippo-SX, Руководство пользователя

Страница: 16 / 68

GENERAL FEATURES
__________________________________
SECONDARY CACHE MEMORY
Although there is 8K bytes internal cache memory
inside the CPU, a secondary cache memory is still
necessary when the size of main memory is large.
In a single user system, when only DOS is used
and few megabytes memory is installed, the internal
cache memory is adequate and the performance is still
very high.
In a multi-user or multitasking environment, CPU
has to switch from one process to another, which
involves a large mount of data transfer. The
performance to a great extent depends on the data
transfer rate. In a 80486SX system, a large portion of
the internal cache memory has to be updated to the
main memory and then the data for another process is
retrieved into the cache memory. The low speed main
memory will substantially slow down the system.
In order to shorten the time required for switching
between processes, a secondary cache memory is
needed as a buffer between the slow speed main
memory and the internal cache memory of 80486SX.
Wait state is thus eliminated when the CPU reads
external data from the secondary cache memory.
Furthermore, the secondary cache memory can support
the burst mode of 80486SX. The CPU is able to run at
full speed.