User`s manual

Hardware Configuration
15
2.4 CACHE CONFIGURATION
The special feature of the mainboard is a built-in direct-mapped cache controller with optional write-
back or write-through operation that supports 128KB, 256KB or 512KB cache memory.
The mainboard has a built-in cache controller. It requires external SRAM as tag and cache memory.
The caching Scheme is direct mapping with selectable write-back or write-through operation. The
mainboard allows 128KB, 256KB, and 512KB cache configurations. Memory size is selected by the
hardware jumpers and the BIOS setup program.
2.4.1 UPGRADING CACHE
The mainboard is available with an optional 128KB, 256KB or 512KB cache memory on-board.
User can upgrade cache memory by installing additional SRAM (Static Random Access Memory)
chips in sockets U1, U2, U3, U4, U5, U6, U7, U8; U11.
The speed of the SRAM chips needed depends on the clock speed of the microprocessor:
25MHz
clock requires
25ns (tag)
and
25ns (data)
SRAM chips.
33MHz, 40MHz, or 50MHz
clock CPU requires
20ns (tag)
and
20ns (data)
SRAM chips.
2.4.2 CACHE SIZE AND MEMORY LOCATIONS
The table below describes the chip capacity and socket location required for each cache size
configuration. User can use 32Kx8-bit or 128Kx8-bit SRAM chips in banks 0 and 1, and in the Tag
RAM socket. Please note that; do not combine different chip capacities in banks 0 and 1.
BANK 0 BANK 1 TAG
RAM
Cache
Size
U1 U2 U3 U4 U5 U6 U7 U8 U11
128K
32Kx8 32Kx8 32Kx8 32Kx8 NONE NONE NONE NONE 8Kx8
256K
32Kx8 32Kx8 32Kx8 32Kx8 32Kx8 32Kx8 32Kx8 32Kx8 16Kx8/
32Kx8
256K
64Kx8 64Kx8 64Kx8 64Kx8 NONE NONE NONE NONE 16Kx8/
32Kx8
512K
128Kx8 128Kx8 128Kx8 128Kx8 NONE NONE NONE NONE 32Kx8
Table 2: Cache Size Configuration