Octek Hippo-SX, Руководство пользователя

Страница: 18 / 68

GENERAL FEATURES
__________________________________
MEMORY SYSTEM
Four banks of DRAMs can be installed. Two banks
are available on motherboard and others are on optional
memory expansion board. The maximum memory size is
32MB when using 4MB DRAM.
The memory system provides a flexible memory
configuration. 256KB and 1MB DRAM can be mixed
together. Several combinations of DRAM types are
allowed. So, a basic system is equipped with 1MB using
256KB DRAM and then memory size is increased to 5MB
by putting another bank of 1MB DRAM.
When using 4MB modules, you may install up to
two banks. So the memory size is either 16MB or 32MB.
4MB module cannot work with other memory types.
The memory system supports page-inter-leaved
mode. The memory is divided into pages. Successive
memory accesses within the same page need not require
wait state. When more than one bank of memory are
installed, the page size is effectively increased because
several banks of memory can be kept active. If four
banks are filled, the page size is increased by a factor of
four.
To enhance the system performance, shadow RAM
mode is supported. In shadow RAM mode, system BIOS
and video BIOS contained in low speed memory such as
EPROM and ROM are copied into DRAM. Improvement is
significant because access to DRAM is mush faster than
ROM.
Another useful feature is memory remapping.
640KB is allocated as base memory. System BIOS and
video BIOS occupy some locations between 640K and
1M. When 1M bytes or more are installed, there are
some parts of DRAM overlapping with the BIOS and
cannot be accessed. Memory remapping allows these
parts of memory to be accessed at other locations and