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Chapter 2 System Overview
Compaq Deskpro 4000N and 4000S Personal Computers
First Edition - September 1997
2-10
2.4.1 MICROPROCESSOR
The Compaq Deskpro 4000N and 4000S Personal Computers feature the Pentium MMX
microprocessor that is backward-compatible with software written for x86-type processors. The
Pentium MMX microprocessor includes a 32 KB L1 cache and extensions to the instruction set
that provide higher performance for processing graphics and video code. The microprocessor is
mounted in a ZIF type-7 socket that allows replacing and/or upgrading.
Figure 2–7.
Microprocessor Architectural Diagram
2.4.2 MEMORY
This system includes 256 kilobytes of SRAM for secondary (L2) cache support of the
microprocessor’s primary (L1) cache. The L2 cache is arranged as direct-mapped, write-through
using synchronous pipelined burst SRAMs.
For system memory two 168-pin DIMM sockets are provided with 16 or 32 megabytes of un-
buffered SDRAM installed depending on model. System memory can be expanded up to 256
megabytes using 8-, 16-, 32-,64-, and 128-MB DIMMs. Both EDO and SDRAM DIMMs are
supported (SDRAM DIMMs are recommended). The system supports the use of ECC memory as
well.
The system ROM utilizes a flash ROM component that contains the BIOS and stores PCI, ESCD,
and EV data. The BIOS is updateable by remote or local flashing of the ROM, which includes
boot block ROM support.
(Mounted in Type 7 Connector)
Pentium MMX Microprocessor
Dual-ALU
CPU w/MMX
Branch
Prediction
Dual Pipeline
Math Coproc.
32-KB
Cache