NEC VERSA S, Service Manual, Page: 16 / 100

Technical Information 1-5
System Board
The system board is inside the base unit. It contains system components including the CPU,
system memory, and I/O subsystems.
Refer to Table Section 1-1 for a summary of the chipsets supported by the Versa S. For a
list of system board connector descriptions, see Appendix A. System board specifications
are listed in at the end of this section.
Table Section 1-1 Versa S Supported Chipsets
Chip Manufacturer Description Technology
i486SX-33 Intel 33 MHz CPU 208-pin QFP*
i486DX2-50 Intel 50 MHz CPU 208-pin QFP*
PT86C368 PicoPower System Controller 208-pin QFP*
FDC37C665 Standard MicroSystem
Corporation Peripheral Controller 100-pin QFP*
28F010 Intel 128-KB Flash ROM 32-pin PLCC**
CL-GD6235 Cirrus Logic VGA Controller 208-pin QFP*
80C51SL Intel Keyboard Controller 44-pin QFP*
CL-PD6720-B Cirrus Logic PCMCIA Controller 208-pin QFP*
*QFP: quad flat package
**PLCC: plastic lead chip carrier
CPU
The CPU is an Intel SL Enhanced i486 chip (DX2-50 or SX-33). The CPU controls im-
portant functions including power management, direct drive bus interface, and memory
management. It has a 32-bit internal data bus and requires an operating voltage of 3.3 volts.
The CPU’s microprocessor has an internal on-chip cache controller with 8-KB cache mem-
ory. The DX2-50's floating point unit (FPU) provides an internal math coprocessor.
Memory
The system board provides 4 MB of standard random access memory (RAM). Optional
memory cards with a value of 4- or 8-MB can be added to increase system memory up to
12 MB.
The system board also provides 128 KB of read-only memory (ROM). The 28F010 flash
ROM contains the system, power management, and video BIOS.