Secondary Cache; System And Video Bios - NEC POWERMATE VE - SERVICE MANUAL 05-1996 Service Manual

1-6 Technical Information

Secondary Cache

The system board contains the connector for an optional 256 KB secondary cache, external
to the processor. The optional cache can be 15-ns asynchronous or 20-ns synchronous
pipeline burst.
Cache allows data to be sent or received from cache with one wait state burst. Cache
memory improves read performance by holding copies of code and data that are frequently
requested from the system memory by the processor. Cache memory is not considered part
of the expansion memory.

System and Video BIOS

The system and video BIOS are stored in a 1 MB (128 KB by 8) flash memory device
(Flash ROM). The system BIOS uses 64 KB, the video BIOS uses 32 KB, and 32 KB is
reserved. The system BIOS is capable of being shadowed and cached through the system's
Setup utility (see Section 2 for Setup information). System BIOS is write protected and
automatically enabled.
The BIOS programs execute the Power-On Self-Test, initialize processor controllers, and
interact with the display, diskette drives, hard disks, communication devices, and
peripherals. The system BIOS also contains the Setup utility. The hardware setup default
copies the ROM BIOS into RAM (shadowing) for maximum performance.
The Flash ROM allows the system and video BIOS to be upgraded with the BIOS Update
utility, without removing the ROM (see Section 2 for further information on the BIOS
Update utility). The Flash ROM supports the reprogramming of the system BIOS and the
video BIOS.
The system memory map is shown in Table Section 1-3.
Memory Space
FFF80000-FFFFFFFF
04000000-07FFFFFF
01000000-03FFFFFF
00F00000-00FFFFFF
00100000-00EFFFFF
000F0000-000FFFFF
000C8000-000EFFFF
Table Section 1-3 System Memory Map
Size Function
512 KB BIOS ROM
64 MB L2 cache (Non-Cacheable with less than 512 KB
SRAM)
L1 cache (Cacheable)
48 MB Always cachable
1 MB Optional memory space gap
14 MB Cachable
64 KB System BIOS (Shadowed in DRAM)
160 KB Expansion region (Shadowed in DRAM)