Hardware Functional Overview 3-3
System BIOS
In AT-compatible systems, system configuration data must be stored somewhere when the
computer is turned off. This data is stored in CMOS RAM. Unlike the DRAM used for
standard system memory, CMOS RAM requires very little power. When the computer is
turned off, a back-up battery powers the CMOS RAM, which retains the system parame-
ters. The computer is configured with values stored in CMOS RAM by the system BIOS,
which gains control when the computer is powered on.
The primary function of the system BIOS (Basic Input-Output System) is to provide a se-
ries of software interrupts, functions, and sub-functions that control operations on certain
devices, such as the hard disk drive, floppy drive, and video subsystem.
The NEC Versa 550 Series uses Phoenix BIOS. The BIOS SETUP program is an easy-to-
use system configuration utility that sets system parameters and resides on the EPROM chip
with the system BIOS.
The EPROM chip also includes BIOS Power-On Self Test (POST) diagnostic and booting
code that tests the system components, initializes certain data structures, and boots the op-
erating system.
System Processor
The System Processor function for the notebook is implemented on the Motherboard using
either the 3.45V Cyrix 486DX4-75MHz (NEC Versa 500D) or the 3.45V Cyrix 5x86
M1sc-100MHz (NEC Versa 550D) Processor Chip. The processor operates in conjunction
with RAM and ROM memory and other system control logic (e.g. UMC 8486F) to process
software instructions (BIOS, Windows, Applications).
The Cyrix M1sc microprocessor is a high performance 586-class CPU which is compatible
with all popular x86 operating systems including DOS, Windows, Windows NT, Windows
95, Unix, Novel, and OS/2. The superpipelined architecture of the integer unit combined
with single cycle execution, branch prediction, 16-Kbyte write-back cache, and single cycle
instruction decode results in true 586-class performance. These features result in a 60 to 90
percent gain in processing speed compared to the Cyrix 486DX2-50).
Additionally, the M1sc CPU provides many power savings features making it ideal for
power sensitive systems like notebook computers. Aside from operating at 3.45V only, the
CPU clock can also be completely stopped. Moreover, the CPU automatically powers down
the FPU and other internal circuits when not in use. Fast entry into and exit from SMM
mode allows frequent use of the SMM feature without noticeable performance degradation.
Summary of Contents for VERSA 500D WINDOWS 98 - UPGRADE INFORMATION
Page 79: ...4 8 Field Service Guidelines ...
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