Hardware Functional Overview 3-3
SYSTEM BIOS
In AT-compatible systems, configuration data must be stored somewhere when the com-
puter is turned off. This data is usually stored in the CMOS RAM. Unlike the DRAM, used
for system memory, the 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 the values stored in the 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, the floppy drive, and the video subsystem.
The NEC Versa 2400 Series uses the Phoenix BIOS. The BIOS SETUP program is an
easy-to-use system utility configuration that sets system parameters and copies them on the
EPROM chip with the system BIOS.
The EPROM chip also includes BIOS Power-On Self Test (POST) diagnostic and booting
codes 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 system board using
an Intel P54LM-100MHz Processor Chip. The processor operates in conjunction with the
RAM and ROM memory plus other system control logic (e.g. UMC 8486F) to process
software instructions (BIOS, Windows, applications).
The Intel P54CSLM microprocessor is a high performance 586-class CPU which is com-
patible with all the popular x86 operating systems including DOS, Windows, Windows NT,
Windows 95, Unix, Novell, and OS/2. The super pipelined 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 P54CSLM 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 and exit from the SMM
mode allows frequent use of the SMM feature without noticeable performance degradation.
Major Functional Blocks
The Intel P54CSLM, in a 320-pin TCP packaging, is divided into five major functional
blocks:
Integer Unit
Floating Point Unit