1-10 Technical Information
The dual processor upgrade option is installed in a 320-pin PGA, zero-insertion-force (ZIF)
socket on the system board.
Secondary Cache
The 16-KB primary cache (8 KB data and 8 KB instruction) is integrated into the
processor. The system board also provides 256 KB of 9-ns, synchronous secondary cache
memory that is external to the processor. 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.
The cache is connected directly to the processor address bus (direct mapped) and uses
physical addresses (32-bit line size). A bus feature known as Burst enables fast cache fills.
Memory areas (pages) can be designated as cacheable or non-cacheable by software. The
cache can also be enabled and disabled by software.
The write strategy of the secondary cache is write-back for single processor systems and
write-through for dual processor systems. If the write is a cache hit, an external bus cycle is
generated and information is written to the cache. Any area of memory can be cached in the
system. Non-cacheable portions of memory are defined by software. The cache can be
cleared by software instructions.
Flash ROM
Machine language programs known as the system's basic input/output system (BIOS) are
stored in a 256K x 8 Flash ROM chip (28F020 PLCC) mounted on the system board. The
system BIOS, EISA extensions, PCI extensions, Automatic Configuration Unit (ACU)
loader, and Video BIOS reside in the upper 64K of the ROM area. The lower 64K of ROM
includes the SCSI BIOS and ACU code.
The flash ROM allows the BIOS to be upgraded with the BIOS Update utility without
removing the ROM (see Section 4, Maintenance and Troubleshooting). The BIOS can only
be reprogrammed by powering on the system with the BIOS Update utility diskette in
drive A.
The BIOS programs execute the Power-On Self-Test (POST), initialize the processor
controllers, and interact with the display, diskette drives, hard disks, communication
devices, and peripherals. The system BIOS also contains the Setup program and provides
VGA controller support. The ROM BIOS is always copied into RAM (shadowing) for
maximum performance.
System BIOS is located between E0000h-FFFFFh and supports shadowing and shadowed
memory. System BIOS is write protected and automatically enabled.
The video BIOS is combined with the system BIOS and is located between C0000h and
C7FFFh. The system memory map is shown in Table Section 1-2.