Model N51 (8551)
RFN51120.EXE PS/Note N51 (SX&SLC) Reference Disk v1.20
DGN51120.EXE N51 (SX & SLC) Diagnostic Disk v1.20
n51vdfix.exe Display Utility N51SX (Thank Heinz Rath for this!)
tpvol1.pdf  L40SX, CL57, N45, N51 HMM
192-065 Model N51 SX System And Features (8551-033) 80386SX-16, 40MB HD
192-072 Model N51 SLC System And Features (8551-025)386SLC-16  w/8KB L1, 80MB HD
192-258  IBM 3550 Expansion Unit Model 001
192-261  IBM High Speed Internal Data/Fax Modem
193-087  IBM High Speed Internal Data/Fax Modem
SHS04G5111     IBM PS/2 Model N51 SX HMR  
SHS04G5112     IBM PS/2 Model N51 SX HMS

8551 Errors
8551 Power

8551 Planar, Top
8551 Planar, Bottom
8551 Supressed Memories
Jim Shorney's modifications for 8MB for N51SX / N51SLC
Remove Power On Password (POP)
LCD / Video
Linux on N51
ADF Sections for planar (minus ESDI)

8551 Planar, Top 

1. LCD Interface Connector
2. System-Expansion Port (120-pin)
3. Keyboard-Control Card Connector
4. Battery Presence Switch
5. LCD Interface Connector
6. LCD Interface Connector

8551 Planar, Bottom

 1. I/O Panel Connector
 2. Voltage Converter Connector
 3. System Expansion Port (120-pin)
 4. Password-Override Connector
 5. Memory-Module Kit Connector
 6. Hard-Disk Drive Connector
 7. Voltage Converter Connector
 8. Hard-Disk Drive Connector
 9. Diskette-Drive Connector
10. Diskette-Drive Connector
11. I/O Panel Connector
12. I/O Panel Connector

8551 Suppressed Memories 
   I think it was. It uses the same 2.5" DF9F version that the CL57 / TP  700 & 720 use too - a typical IBM part to be found nowhere else than in "True Blue" units.

The harddisk is a INTEGRATED ESDI adapter (DF9F like a TP720)

Steven Gorenbergh (in a sotto voice) whispers-
   I bought my N51 and docking station in 1994 when IBM was selling all 80386 (and lower) machines to the employees.
   I recall at least 1 review of the N51 by PC Magazine by Bill MacCrone in the 1993 time frame. He generally liked many things about the machine, but thought that it was under powered.
   The N51 was also displayed on the cover of the 1993 IBM PC Catalog along with the P70 and CL57,
   The N51 was one of the first IBM notebook machines designed and made in Japan (along with the CL57). These machines are the immediate parents to the IBM ThinkPad 700 / 720 family.  The IBM ThinkPad 700 has the same form factor as the N51 (both have similar but different docking stations) and a still impressive 10" VGA color display.

Exuntcfg.exe Expansion Unit Configuration Utility

Remove Power-on Password (POP)
1. Power-off 8551 and unplug power cord. 
2. Remove bottom cover and battery pack. 
3. Locate override connector on planar. 
4. Install jumper over pins as shown. 
5. Power-on computer to erase password. 
6. Remove jumper after POST completes. 
    (Or you won't be able to reset a POP)

Internal Communications Options
Internal Data/Fax Modem  P/N 94X2555 / FRU 53G7772   (2400b data/9600b fax).
Serial Adapter  P/N 79F6800 / FRU 79F6840 
   The IBM PS/2 Internal Data/Fax Modem and IBM PS/2 Serial Adapter optional features use the same internal connector so only one of these options can be installed per system.

High Speed Internal Data/Fax Modem  P/N 42G2580
   Full function, auto-dialing, auto-answering, data/fax modem.  It is an international modem with error correction, data compression and power management capabilities. V.32bis Data (300-14400bps)/V.17 FAX (300-14400bps The modem has the ability to facilitate an acoustic coupler
   The IBM High Speed Internal Data/Fax Modem is compatible with the existing IBM Internal Data/Fax modem (2400b data/9600b fax).  It has the same physical form-factor and support the same application interfaces.

LIMITATIONS:  V.42bis data compression is limited by applications that utilize the BIOS controlling the serial port.  Data compression for applications that do not bypass the BIOS is limited to 19.2K bps.
   Many applications bypass the BIOS.  Hence, they allow data compression approaching the theoretical limit of 57.6K bps, or four times data compression.

Modem Init Strings
IBM N51 Laptop 14400 AT&F&C1&D2J0N7Q3V2%C1
IBM N51 Laptop 9600 AT&F&C1&D2J0N7Q3V2%C1
IBM PS/2 Data/Fax Modem AT&F&C1&D2Q3N3J0V1

1 Serial (It seems that the chips for a second serial are already on board because all programs detect two ports!) So i think that the adapter for the second port was only a simple adapter with the connector to the outside.

1 Parallel port can be used in Standard and PS/2 mode (For ZIP drives for example)

Liquid Crystal Display
   Easy to read, 9.5-inch Liquid Crystal Display (LCD) with 640 x 480 Video Graphic Array (VGA) resolution, and cold fluorescent backlighting.  Depending on the application, up to 32 grey scales can be addressed on the LCD.  The LCD displays black characters on a white background with 80 characters per line and 25 lines per screen.  This black on white can be reversed to a white on black mode by a simple switch "reverse" mode operation.

When the VGA port is operational, the integrated LCD is not operational. The VGA card has 256 KB Ram and seems to be a WD90C00. Maximum Resolution 640x480

Memory Configurations
   Each IBM PS/2 Model N51 SLC has 2MB of memory soldered to the planar.  There is one memory expansion socket available.  Memory options (2MB, 4MB and 8MB) support memory configurations of 2 (standard), 4, 6 and 10MB.

2MB Memory Module   P/N 07G1826
4MB Memory Module   P/N 07G1827 
8MB Memory Module   P/N 07G1828

Communications Cartridge P/N 07G2580
   External expansion port that can accommodate a half-size adapter.  It also contains an AC adapter that converts power to DC and provides low power to the cartridge.  The communications cartridge attaches directly to the PS/2 note without using a bus cable.

IBM PS/2 Miniature Mouse  P/N 07G0033
IBM PS/2 Numeric Keypad   P/N07G0032
   Pointing device port for the external numeric keypad, or the IBM PS/2 Miniature Mouse.  The numeric keypad also has a mouse port to enable both numeric keypad and pointing device connections concurrently.
o   External keyboards are not supported.

Linux on the N51
From  Heinz Rath
   The following infos i have from running Linux (Kernel 2.0.35) on this
machine. The boot parameter reboot=bios is needed so that no crash happens. My 40MB harddisk isn't detected correct so i set the following parameters eda=38,32,64. With this settings the ESDI disk worked under this kernel.

With Kernel 2.2.17 the harddisk is still not correct identified. I haven't tested if the boot parameter (eda) is correct because i booted from a Zip disk and didn't use the ESDI disk with this kernel.

X11 Settings
For X11 i used the following settings.
Section "Monitor"
   Identifier  "LCD"
   VendorName  "IBM"
   ModelName   "N51sx"
   HorizSync   43.03
   VertRefresh 81.99
   ModeLine  "640x480" 28.32 640 656 720 658 480 480 486 525
Section "Device"
   Identifier  "VGA"
   VendorName  "IBM"
   BoardName   "N51sx"
   Chipset     "generic"
   VideoRam    256
   Clocks      28.32

This settings worked for me with the Mono server. I can not guarantee that
the settings are correct because i have found them in the following way. I took the XF86Config file of a TP 300 which i have found in Internet and then i changed it until the server started and i got a screen on the display.

AdapterId F1FE Built In Features

Serial Port A
   The serial port can be assigned as Serial 1, Serial 2, or disabled. 
      <"SERIAL_1,IRQ4"  (io 03f8-03ff 083f8-083ff int 4)>, 2,IRQ3 (02f8-02ff 082f8-082ff int 3), Disabled

Serial Port B
   The serial port can be assigned as Serial 1, Serial 2, or disabled. 
      <SERIAL_2,IRQ3 (io 02f8-02ff 082f8-082ff int 3)>, Disabled, 1,IRQ4 (io 03f8-03ff 083f8-083ff int 4)

Parallel Port
   The parallel port  can be assigned as Parallel 1 through 4 or disabled. 
      <choice vcheck "PARALLEL 1"  (io 03bc-03bf 1278-127b int 7)>, 2 (0378-037b int 7), 3 (0278-027b int 7), 4 (1378-137b int 7), Disabled

Parallel Port Arbitration Level
   The parallel port can be assigned an arbitration levels of 0 through 7. Select <Disabled> to use the parallel port in compatibility mode.
      <choice vcheck "Level 6>, 5, 4, 3, 1, 0, Disabled, 7

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