NEC POWERMATE OFFICE 2513 - SERVICE, Руководство по обслуживанию

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1-10 Technical Information
Processor
The PowerMate Office computers use the following Pentium processors:
„
133-MHz processor with an internal speed of 133 MHz and an external speed of
66 MHz (2513 models)
„
166-MHz processor with an internal speed of 166 MHz and an external speed of
66 MHz (2516 models).
Each processor has 16 KB of write-back primary cache and a math coprocessor. The 16-
KB primary cache provides 8 KB for instructions and 8 KB for data.
The processor is an advanced pipelined 32-bit addressing, 64-bit data processor designed to
optimize multitasking operating systems. The 64-bit registers and data paths support 64-bit
addresses and data types.
To use the Pentium processor’s power, the system features an optimized 64-bit memory
interface and complementary asynchronous 256-KB secondary cache.
The processor is compatible with 8-, 16-, and 32-bit software written for the Intel386™,
Intel486™, and Pentium processors.
To accommodate future technologies and work requirements, the Pentium processor comes
in a 321-pin zero insertion force (ZIF) socket. The socket provides an upgrade path to the
next generation processor.
Secondary Cache
All models contain 256 KB of asynchronous secondary cache on the system board, external
to the processor. The cache uses 15-ns SRAM that 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 part of the expansion memory.
The cache is connected directly to the processor address bus and uses physical addresses. 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 cache (primary and secondary) is write-back. If the write is a
cache hit, an external bus cycle is not 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.