NEC 2600 User manual

NEC Versa 2600 Series
Service Guide
Art Copy Version

First Printing — May 1997
Copyright 1997
NEC Computer Systems Division, Packard Bell NEC, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719
All Rights Reserved
PROPRIETARY NOTICE AND LIABILITY DISCLAIMER
The information disclosed in this document, including all designs and related materials, is
the valuable property of NEC Computer Systems Division, Packard Bell NEC, Inc.
(NECCSD, PBNEC) and/or its licensors. NECCSD and/or its licensors, as appropriate, re-
serve all patent, copyright and other proprietary rights to this document, including all de-
sign, manufacturing, reproduction, use, and sales rights thereto, except to the extent said
rights are expressly granted to others.
The NECCSD product(s) discussed in this document are warranted in accordance with the
terms of the Warranty Statement accompanying each product. However, actual
performance of each such product is dependent upon factors such as system configuration,
customer data, and operator control. Since implementation by customers of each product
may vary, the suitability of specific product configurations and applications must be
determined by the customer and is not warranted by NECCSD.
To allow for design and specification improvements, the information in this document is
subject to change at any time, without notice. Reproduction of this document or portions
thereof without prior written approval of NECCSD is prohibited.
NEC is a registered trademark of NEC Corporation;
Versa is a U.S. registered trademark of NEC Technologies, Inc.;
all are used under license by NEC Computer Systems Division (NECCSD), Packard Bell NEC, Inc.
All other product, brand, or trade names used in this publication are the trademarks or registered
trademarks of their respective trademark owners.

iii
Contents
Preface......................................................................................................................... ix
Abbreviations............................................................................................................... xi
Section 1 Technical Information
Hardware Overview — Front.......................................................................................1-2
Liquid Crystal Display (LCD)................................................................................1-2
Power Button .......................................................................................................1-4
Power and Status LEDs........................................................................................1-4
Keyboard..............................................................................................................1-5
NEC VersaGlide...................................................................................................1-5
CD-ROM Reader and Diskette Drive....................................................................1-6
Hardware Overview — Right Side...............................................................................1-6
PC Card Slots.......................................................................................................1-7
Kensington Lock...................................................................................................1-7
Hardware Overview — Left Side.................................................................................1-7
Hardware Overview — Rear........................................................................................1-8
Infrared Port.........................................................................................................1-8
Keyboard/Mouse Port...........................................................................................1-8
Expansion Port .....................................................................................................1-8
Monitor (Video) Port............................................................................................1-8
Parallel Port (LPT1)..............................................................................................1-8
Serial Port (COM1) ..............................................................................................1-9
AC/DC Power Port...............................................................................................1-9
Hardware Overview — Internal Components...............................................................1-9
Battery Pack.........................................................................................................1-9
Hard Disk Drive....................................................................................................1-10
Diskette Drive.......................................................................................................1-10
10x CD-ROM Reader...........................................................................................1-10
CPU Board...........................................................................................................1-11
Sound Board.........................................................................................................1-12
I/O Board .............................................................................................................1-13
Bridge Battery......................................................................................................1-13
System Memory...........................................................................................................1-14
Memory Map........................................................................................................1-14
System Video...............................................................................................................1-15

iv Contents
Parallel Interface..........................................................................................................1-15
Serial Interface.............................................................................................................1-16
NEC Versa Chip Set....................................................................................................1-16
Intel Pentium P55CLM Microprocessor................................................................1-16
256K X Flash ROM..............................................................................................1-16
ROM BIOS....................................................................................................1-17
VGA Controller....................................................................................................1-17
Keyboard Controller .............................................................................................1-18
PC Card Controller...............................................................................................1-18
Sound Integrated Circuit.......................................................................................1-18
Interrupt Controllers.............................................................................................1-19
Power Management Overview .....................................................................................1-20
System Power Management ..................................................................................1-21
Local Power Management.....................................................................................1-21
Plug and Play...............................................................................................................1-21
Specifications...............................................................................................................1-22
Section 2 Setup and Operation
Unpacking the System..................................................................................................2-1
Hardware Setup...........................................................................................................2-1
Cable Connections................................................................................................2-3
Power Sources.............................................................................................................2-4
Using the AC Adapter...........................................................................................2-4
Using the Main Battery Pack.................................................................................2-5
Installing the Battery Pack..............................................................................2-5
How to Recharge the Battery Pack.................................................................2-6
Battery Handling...................................................................................................2-6
Replacing the Battery Pack ............................................................................2-7
Battery Life...........................................................................................................2-8
Extending Battery Life...................................................................................2-8
Battery Charging............................................................................................2-9
Battery Precautions........................................................................................2-9
Battery Disposal.............................................................................................2-10
Internal Batteries...................................................................................................2-10
Extending Battery Life..........................................................................................2-10
Operating Controls ......................................................................................................2-11
Status Icons and LEDs..........................................................................................2-12

Contents v
Status Icons...................................................................................................2-12
Function Keys (Fn Keys).......................................................................................2-13
Updating the System BIOS ............................................................................2-13
Power-On Self -Test (POST).......................................................................................2-14
POST Errors.........................................................................................................2-15
Setup Utility ................................................................................................................2-16
Setup Utility..........................................................................................................2-17
How to Enter Setup.......................................................................................2-17
How to Use Setup..........................................................................................2-17
The Setup Screen...........................................................................................2-17
Using Keys ...........................................................................................................2-18
Checking/Setting System Parameters..............................................................2-19
Using Power Management ....................................................................................2-25
Power Saving Modes.....................................................................................2-25
Power Management Settings..........................................................................2-26
Using Fn-F3...................................................................................................2-26
Section 3 Troubleshooting
Quick Troubleshooting ................................................................................................3-1
Helpful Questions ........................................................................................................3-4
Section 4 Field Service Guidelines
Preventive Maintenance ...............................................................................................4-1
Cleaning the Notebook Exterior............................................................................4-2
Cleaning the Notebook Interior.............................................................................4-2
Protecting the Disk Drives ....................................................................................4-2
Handling the Battery Packs...................................................................................4-3
Maintaining the LCD Quality................................................................................4-3
Disassembly and Reassembly........................................................................................4-4
Required Tools and Equipment ............................................................................4-5
Battery Pack.........................................................................................................4-5
Hard Disk Drive....................................................................................................4-6
Keyboard..............................................................................................................4-7
Heat Shield and CPU Board..................................................................................4-9
LCD and Top Cover.............................................................................................4-11
VersaGlide Assembly............................................................................................4-13
Sound Board.........................................................................................................4-14

vi Contents
LED Status Board and IR Board...........................................................................4-14
10X CD-ROM Reader and Heat Shield.................................................................4-14
Bridge Battery and Diskette and Hard Drive Connector Board..............................4-16
Diskette Drive.......................................................................................................4-17
Power Board.........................................................................................................4-18
Main Board...........................................................................................................4-18
Reassembly ..........................................................................................................4-18
Illustrated Parts Breakdown.........................................................................................4-18
Service Information......................................................................................................4-22
Technical Support........................................................................................................4-22
Product Information.....................................................................................................4-23
Ordering Information from FaxFlash............................................................................4-23
Appendix A Connector Locations and Pin Assignments
Appendix B Video Modes
List of Figures
1-1 NEC Versa 2600 Series Notebook................................................................. 1-1
1-2 Front View..................................................................................................... 1-3
1-3 Keyboard Layout ........................................................................................... 1-5
1-4 VersaGlide Location...................................................................................... 1-6
1-5 Right Side Features........................................................................................ 1-6
1-6 Left Side Features.......................................................................................... 1-7
1-7 Rear Features................................................................................................. 1-8
1-8 CPU Board Layout ........................................................................................ 1-11
1-9 Sound Board Layout...................................................................................... 1-12
1-10 I/O Board ...................................................................................................... 1-13
2-1 AC Adapter ................................................................................................... 2-1
2-2 Powering On the System................................................................................ 2-2
2-3 Power and I/O Connector Locations .............................................................. 2-3
2-4 NEC Versa AC Adapter................................................................................. 2-4
2-5 Battery Release Latch ................................................................................... 2-7
2-6 Inserting Battery Pack.................................................................................... 2-8
2-7 Panel LEDs and Controls............................................................................... 2-11

Contents vii
2-8 Status Icons................................................................................................... 2-12
4-1 Releasing the Battery Pack............................................................................. 4-5
4-2 Removing the Hard Disk Drive (Step1).......................................................... 4-6
4-3 Removing the Hard Disk Drive (Step 2)......................................................... 4-6
4-4 Removing the Hard Disk Drive (Step 3)......................................................... 4-7
4-5 Removing the Keyboard................................................................................. 4-8
4-6 Removing the Heat Sink/Shield Subassembly ................................................. 4-9
4-7 Removing the CPU Board.............................................................................. 4-10
4-8 Removing the LCD Assembly (Step 1)........................................................... 4-11
4-9 Removing the LCD Assembly (Step 2)........................................................... 4-12
4-10 Disconnecting VersaGlide Cables................................................................... 4-13
4-11 Removing the CD-ROM Reader..................................................................... 4-15
4-12 Removing the CD-ROM Reader Assembly Screws......................................... 4-15
4-13 Removing the Bridge Battery and Diskette and Hard Drive Connector Board. 4-17
4-14 NEC Versa 2600 Series Illustrated Parts Breakdown...................................... 4-19
A-1 CPU Board Layout ........................................................................................ A-1
A-2 Main Board Layout........................................................................................ A-2
A-3 Sound Board Layout...................................................................................... A-3
List of Tables
1-1 Model Configurations NEC Versa 2600 Series............................................... 1-2
1-2 Memory Map................................................................................................. 1-14
1-3 NEC Versa 2600 Series Chip Types and Technologies................................... 1-16
1-4 Interrupt Controllers...................................................................................... 1-19
1-5 DMA Channel................................................................................................ 1-20
1-6 Automatic Power-Saving Features ................................................................. 1-20
1-7 Specifications................................................................................................. 1-22
2-1 I/O Connector Descriptions............................................................................ 2-3
2-2 Control and Switch Functions ........................................................................ 2-11
2-3 Fn Key Operations......................................................................................... 2-13
2-4 POST Error Messages.................................................................................... 2-15
2-5 Setup Key Functions...................................................................................... 2-18
2-6 Setup Parameters........................................................................................... 2-19
2-7 Automatic Power-Saving Features ................................................................. 2-26

viii Contents
3-1 Quick Troubleshooting................................................................................... 3-1
4-1 NEC Versa 2600 Series Disassembly Sequence.............................................. 4-4
4-2 NEC Versa 2600 Series Field-Replaceable Parts............................................. 4-20
4-3 NEC Service and Information Telephone Numbers......................................... 4-22
A-1 CPU Board Connector................................................................................... A-1
A-2 Main Board Connectors................................................................................. A-2
A-3 Sound Board Connectors............................................................................... A-3
A-4 Keyboard/Mouse Connectors......................................................................... A-3
A-5 Serial Port Connector Pin Assignments .......................................................... A-4
A-6 CRT Connector Pin Assignments ................................................................... A-4
A-7 Parallel Printer Pin Assignments..................................................................... A-5
A-8 Power Connector........................................................................................... A-5
A-9 Hard Disk Drive Connector............................................................................ A-6
B-1 LCD Display Mode Setting (800x600 TFT Color LCD
and Simultaneous CRT Display)..................................................................... B-1
B-2 CRT Display Mode (CRT Only)..................................................................... B-3
B-3 Panning Video Mode (800x600 TFT Color LCD and
Simultaneous CRT Display) ........................................................................... B-4

ix
Preface
This service and reference manual contains the technical information necessary to set up and
maintain the following NEC Versa®2600 Series models:

NEC Versa 2630CD

NEC Versa 2635CD

NEC Versa 2650CD
 NEC Versa 2655CD

NEC Versa 2650CDT
 NEC Versa 2655CDT.
The manual also provides hardware and interface information for users who need an over-
view of the system design. The manual is written for NEC-trained customer engineers, sys-
tem analysts, service center personnel, and dealers.
The manual is organized as follows:
Section 1 Technical Information, provides an overview of the hardware and interface
components. System specifications are listed including computer dimensions, weight, envi-
ronment, safety compliance, power consumption, and system memory specifications.
Section 2  Setup and Operation,takes the authorized service technician or dealer from
unpacking to setup and operation. The section includes a description of operating controls,
setting parameters and accessing the NECCSD bulletin board system (BBS).
Section 3  Troubleshooting, lists troubleshooting procedures as well as helpful
servicing hints.
Section 4  Field Service Guidelines,provides disassembly and assembly procedures,
and an exploded-view diagram of the NEC Versa system with part numbers.
Appendix A  Connector Locations and Pin Assignments,provides a list of the main
board internal connector pin assignments and a list of external pin assignments.
Appendix B  Video Modes,lists NEC Versa supported video modes.
An Index is included for convenience.

Section 1
Technical Information
The NEC Versa 2600 Series notebook computers are lightweight, compact, and fully IBM
compatible. The latest additions to the NEC Versa 2600 family include the following
models:
 NEC Versa 2630CD
 NEC Versa 2635CD
 NEC Versa 2650CD
 NEC Versa 2655CD
 NEC Versa 2650CDT
 NEC Versa 2655CDT.
NOTE
This service manual covers the NEC
Versa 2630CD, 2635CD, 2650CD, 2655CD,
2650CDT, and 2655CDT models only. All fig-
ures in this manual reflect these models.
Figure Section 1-1 NEC Versa 2600 Series Notebook
This section of the manual provides system configuration information, including an over-
view of hardware and interface components. See the following table for a system specific
breakdown of each model’s hardware.

1-2 Technical Information
Table Section 1-1 Model Configurations NEC Versa 2600 Series
Feature 2630CD 2635CD 2650CD 2655CD 2650CDT 2655CDT
CPU (Pentium) P54CSLM
133 MHz P55CSLM 133 MHz P55CL, 150 MMX P55CL, 150 MMX P55CL, 150 MMX P55CL, 150 MMX
On-Board RAM 16 MB 16 MB 16 MB 16 MB 16 MB 16 MB
Video Memory 1.5 MB 1.5 MB 1.5 MB 1.5 MB 1 MB 1 MB
Hard Disk Drive 1.44 GB 1.44 GB 1.44 GB 1.44 GB 1.44 GB 1.44 GB
CD-ROM Reader 10X 10X 10X 10X 10X 10X
Color LCD (12.1”) SVGA1,
DSTN2SVGA1, DSTN2SVGA1, DSTN2SVGA1, DSTN2SVGA1, TFT3SVGA1, TFT3
Battery NiMH NiMH NiMH NiMH LiIon LiIon
1. Super VGA (SVGA) color display
2. Dualscan Super-Twisted Nematic (DSTN)
3.Thin Film Transistor (TFT)
HARDWARE OVERVIEW—FRONT
Take a moment to become familiar with the location and function of controls located on the
front of the system.
Liquid Crystal Display (LCD)
The LCD operates with the Chips & Technologies 65550B VGA controller. The controller
supports Super VGA, uses a 64 bit accelerator with a Peripheral Component Interconnect
(PCI) interface. The LCD also supports VESA timing.
The NEC Versa 2630CD, 26535CD, 2650CD and 2655CD LCD features the following:

12.1-inch Dual-STN, Cold Cathode Fluorescent Tube (CCFT) Super VGA color
LCD

0.30 mm dot pitch

16-bit digital interface

800 x 600 resolution

64,000 colors

Slide bar that adjust screen contrast.
The NEC Versa 2650CDT and 2655CDT features the following:

12.1-inch active-matrix Thin Film Transistor (TFT), Super VGA (SVGA) backlit
color LCD

0.3 mm dot pitch

Technical Information 1-3

18-bit digital interface

800 x 600 resolution

64,000 colors

Slide bar that adjust screen brightness.
Additional LCD panel features include a slide switch which controls adjusts screen bright-
ness.
Figure Section 1-2 Front View
Another video feature includes a CRT port on the system's rear panel that allows the user to
connect an optional monochrome or color external display to the system. The computer can
support the LCD and external display simultaneously.
CD-ROM Reader Diskette Drive
Battery Bay
Power
Button
LCD Panel
Status
LEDs
LCD Slide Bar
VersaGlide
SpeakerSpeaker
Microphone Hard Drive
NEC

1-4 Technical Information
Power Button
Press the power button to power on and power off the computer. The power button is a
“smart” switch, meaning that it recognizes when the system is in Suspend mode. If in Sus-
pend mode, you cannot power off until you press the power button again to bring the sys-
tem out of Suspend mode, then you are able to power off.
Power and Status LEDs
The Power and Status LEDs are situated right below the LCD. They provide an easy way
to detect system status. Power and Status LEDs (identified by icons) are found to the right
of the Power button and inform you of the status of your system and its components. Status
LEDs have the following meanings and light under the conditions noted:
Status LED icons

Power – Lets you know that power to the system is turned on. This LED is posi-
tioned so that you see the power state whether the LCD panel is opened or closed
lights green when the system is powered on.
lights amber when battery power is below 10%.
flashes amber when battery power is below 5%.
!
CAUTION
Be sure to save your data immediately when the
Power LED turns to yellow, flashes yellow, or
the system beeps. Failure to do so can result in
data loss.

Hard Disk Drive – Lights when the NEC Versa 2600 writes data to or retrieves
data from the hard disk drive.

CD-ROM Reader – Lights when data is read from a compact disc in the CD-
ROM drive.
A
Power Hard
Disk Drive CD-ROM Reader Diskette Drive
Caps
Lock Num Lock Pad Lock Battery

Technical Information 1-5

Diskette Drive – Lights when data is written to or retrieved from the 3.5-inch
diskette drive.

Caps Lock – Lights when Caps Lock mode is in effect.

Num Lock – Lights when Num Lock mode is active.

Pad Lock – Lights when the embedded numeric keypad lock is on.

Battery Charging Status – Lights to indicate the following:
Green – the battery is fully charged.
Amber – the battery is charging.
Light Off – the AC adapter is disconnected.
Keyboard
The built-in, 83-key keyboard (U.S.) or 79-key keyboard (UK and Germany) uses the stan-
dard QWERTY format. The keyboard provides 12 function keys and 7 cursor control keys,
with an Fn key for ROM-based key functions. The numeric keypad is embedded in the stan-
dard key layout.
Figure Section 1-3 Keyboard Layout
NEC VersaGlide
The NEC VersaGlide is a built-in mechanism that functions as the system’s mouse. It con-
trols the on-screen pointer (cursor). To use the VersaGlide, move your finger across the
NEC VersaGlide pad, and the cursor follows. The buttons below the NEC VersaGlide al-
low the user to select or deselect menu items. Tap and double-tap are supported on the
VersaGlide pad.
The PS/2 Microsoft mouse is the system’s default pointing device, driver for the NEC Ver-
saGlide. If an external mouse is installed, then the VersaGlide is deactivated. A serial
mouse is not supported.
Function Keys
Control Keys Embedded Numeric Keypad Cursor Control Keys
Esc
Setup
F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 Pause
Break
Ins Del
PrtSc
SysReq
!
1
@
2
#
3
$
4
%
5
^
6
&
7
*
8
(
9
)
0
_
-+
=BkSp
Scroll Lock
Home
PgUp
PgDn
End
Tab QWERTYUI OP{
[
}
]
|
\
Shift
ASDFGHJKL:
;
"
'Enter
Cap
Lock
ZXCVBNM<
,
>
.
?
/Shift
Fn Ctrl Alt Alt Ctrl ~
`
78 9 -
45 6 +
12 3 *
0./

1-6 Technical Information
Figure Section 1-4 VersaGlide Location
CD-ROM Reader and Diskette Drive
A 10X CD-ROM reader and 1.44-MB diskette drive come installed in the NEC Versa
2600 Series on the front of the computer.
HARDWARE OVERVIEW—RIGHT SIDE
Review the following section for a description of the hardware on the right side of the NEC
Versa.
Figure Section 1-5 Right Side Features
VersaGlide
Right
Selection Button
Left
Selection Button
PC Card
Slots Kensington Lock Port

Technical Information 1-7
PC Card Slots
The PC card slot compartment houses two Type II devices, or one Type II and one Type III
devices. For Type III cards, insert the PC card into the upper slot. Insert the card with the
pin sockets facing towards the drive and the label facing up. To remove the PC card, push
on the Eject button to release the pin connections and slowly pull out the card.
The NEC Versa also comes with DOS/Windows PC card drivers for supporting various PC
cards like modem and network cards in Windows for Workgroups configurations.
Kensington Lock
The Kensington Lock Port gives the user the option to add an optional Kensington Lock.
HARDWARE OVERVIEW—LEFT SIDE
Review the following section for a description of the hardware on the left side of the NEC
Versa.
Figure Section 1-6 Left Side Features

Line-In — Use a cable to connect to the Line-Out port on the other audio system
to record or play.

Microphone (MIC) — Connects an external microphone for monophonic record-
ing or amplification through the unit. Plugging in an external microphone disables
the built-in microphone.

Headphones — Connects external headphones or speakers to the NEC Versa.
Plugging in headphones disables the built-in system speakers.

Volume Control — Controls the speaker or headphone volume.
Line In
Microphone Volume
Control Dial
Headphones

1-8 Technical Information
HARDWARE OVERVIEW—REAR
Review the following section for a description of the hardware on the rear of the NEC
Versa.
Figure Section 1-7 Rear Features
Infrared Port
This port lets you transfer files between your NEC Versa and an IR-equipped desktop or
notebook computer. You can also print to an IR-equipped printer without using cables.
Keyboard/Mouse Port
Use the standard PS/2 port to connect an external PS/2-style mouse or a PS/2-style key-
board to the system. A serial mouse is not supported through this connector nor is a Y-
adapter.
Expansion Port
This port provides a connection for NEC Versa options including the NEC Versa Port Rep-
licator 2600.
Monitor (Video) Port
Use this 15-pin port to attach an external monitor to your NEC Versa. You can run the
LCD display and the external monitor simultaneously or run either alone.
Parallel Port (LPT1)
The 25-pin printer port provides a parallel interface to which you can connect a parallel
printer or pocket network adapter. Use this port to connect a parallel printer or other par-
allel device. The port is IEEE 1284 compatible. It supports bi-directional (AT) mode, En-
hanced Capabilities Port (ECP) mode, Enhanced Parallel Port (EPP) mode, (365SL-
compatible), and bi-directional (PS/2) mode.
Serial
Port
AC Power
Port
Parallel
Port
Monitor
Port
Expansion
Port
Keyboard
Mouse Port
Port
Replicator Latch
IR Port

Technical Information 1-9
The parallel port’s default is PS/2 mode. Use Setup to change the default to one of the fol-
lowing.

Standard

EPP

ECP
Serial Port (COM1)
The 9-pin serial port provides a serial interface to which you can connect an RS-232C de-
vice such as an external serial printer or modem. A serial mouse is not supported.
AC/DC Power Port
Use the power jack to attach the NEC Versa to an appropriate DC power source, such as
the NEC Versa 2600 AC adapter or the optional NEC Versa 2600 DC car adapter.
HARDWARE OVERVIEW—INTERNAL COMPONENTS
Review the following sections for a description of the system’s internal hardware.
Battery Pack
The system uses a rechargeable lithium-ion (Li-Ion) battery or rechargeable nickel metal-
hydride (NiMH) as its transient power source. The battery pack installs in the compartment
next to the CD ROM reader on the front of the NEC Versa. The Li-Ion battery stores 14.4
volts with a 2700 mAh capacity and the NiMH stores 9.6 volts with a 3500 mAh capacity.
The battery pack powers the NEC Versa for approximately 1:40 to 4 hours depending on
battery type and power management choice.
When battery power is getting low, connect the AC adapter to a wall outlet and recharge
the battery. It takes 3 to 4 hours to recharge the battery.

1-10 Technical Information
Hard Disk Drive
A removable 2.5-inch, 1.44-GB hard disk drive ships with the system. The 1.44-GB hard
disk drive specifications are listed next.
The 1.44-GB hard disk drive specifications are listed next.

Track-to-track seek rate — 4 ms

Average seek time — 13 ms (read), 14 ms (write)

Revolutions per minute — 4009

Data transfer rate — 16.6 MB/sec

Media data rates — 39.6 − 61.8 Μbit/sec
Diskette Drive
The 3.5-inch 1.44-MB diskette drive is located in the front right of the system.
10X CD-ROM Reader
A 10X CD-ROM reader ships with all NEC Versa 2600 Series models. This ten-speed CD-
ROM reader features the latest in CD-ROM technology. It is located in the front center of
the system. The CD-ROM reader operates at different speeds depending on whether the CD
in use contains data or music. This improves video and sound quality.

Technical Information 1-11
CPU Board
The CPU board is an L-shaped board situated under the keyboard.
The NEC Versa 2630CD and 2635CD models ship with Intel’s P54CSLM/133 MHz with
66 MHz bus speed. Modes 2650CD, 2655CD 2650CDT and 2655CDT ship with
P55CLM/150 MHz MMX with 60 MHz bus speed.
Figure Section 1-8 CPU Board Layout