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'Lightning' Motherboard Layout

Note: Lightning incorporates Intel 440LX chipset (66MHz system bus)
Lightning BX incorporates Intel 440BX chipset (66 or 100MHz system bus)


Front View


1 Infra-red sensor 10 Universal Serial Bus (USB) port
2 Hard disk activity indicator 11 FireWire port (factory option)
3 Power Mode light 12 S-Video In port (factory option)
4 Power button 13 Composite Video In port (factory option)
5 CD-ROM disc drawer (platter) 14 CD emergency eject hole
6 CD headphone jack & volume control 15 CD Eject button
7 CD activity indicator 16 Diskette drive
8 Line In socket for audio input 17 Message LED alerts you that you have an unread message
9 Headphones socket 18 Message Cancel button clears the Message LED alert



1 Power button 6 CD phono jack & volume control
2 CD Eject button 7 Diskette drive
3 CD emergency eject hole 8 Infra-red sensor (optional)
4 CD-ROM disc drawer (platter) 9 Hard disk activity indicator
5 CD activity indicator    

Rear View


1 Monitor port 12 AC power outlet for monitor
2 S-Video Out port for displaying the monitor image on a television (factory option) 13 Voltage selection switch
3 Parallel (printer) port 14 AC power inlet from AC supply
4 Mouse port 15 Caselock
5 Keyboard port 16 MIDI/Joystick port
6 Serial port 17 Auxiliary Line In socket (factory option)
7 Microphone socket 18 SPDIF digital audio output for sending digital audio to an external audio amplifier (factory option)
8 Line Out socket for audio output 19 Modem port
9 Speaker socket    
10 Universal Serial Bus (USB) port A Side panel fixing screws
11 Security loop for cable or padlock B Handles to assist side panel removal




Casing screws for the top cover


Parallel (printer) port


AC power outlet for monitor


Video out port (option)


Voltage selection switch


Monoitor port


AC power inlet from AC supply


PCI slot (full-length)


Double USB port 16 ISA slot (full-length)
6 Audio output (speaker) jack 17 ISA slot (half-length)
7 Audio line-out jack 18 PCI slots (two half-length)
8 Microphone input jack 19 Serial port 2 (optional)
9 Serial (modem) port 1 20 Security loop for cable or padlock
10 PS/2 Keyboard port 21 Caselock (key supplied)
11 PS/2 Mouse port    



1 Auxiliary Line In internal connector (option) 12 Front panel conn. option
2 1.44MB diskette drive connector 13 Processor slot
3 S/P Dif. (option) dig. audio 14 DIMM sockets
4 CD audio connector 15 Case fan connector
5 Front panel USB internal connector (option) 16 CPU fan connector
6 Primary E-IDE connector 17 Processor heat sense input
7 Secondary E-IDE connector 18 VEC/AMC feature connector
8 PSU logic connector 19 TV tuner connector (option)
9 ‘Wake on LAN’ connector 20 Video memory upgrade socket
10 "Wake on Call" Modem connector 21 Riser board connect
11 CMOS battery 22 Motherboard power connector
    23 COM2 interface (option)
J1 On-board video enable/disable A Monitor port
J2 BIOS program enable/disable B TV Out (S-Video) port (factory option)
J5-8 Processor clock multipliers C Parallel (printer) port
J9 DSP enable/disable (option) D PS/2 Mouse port
J10 Audio subsystem enable/disable E PS/2 Keyboard port
J11 Red power LED enable/disable F Serial port COM1
J12 Clear CMOS G Microphone socket
PL4 Server management (option) H Line Out socket
PL18 Joystick/MIDI internal connector I Speaker socket
PL19 Voice modem audio connector J Dual USB port
PL23 Front panel controls/options    
PL25 Internal case speaker (if fitted)    
PL26 Message light (option)    
PL27 Message switch (option)    


You can give your PC more memory by adding or replacing memory modules called Dual Inline Memory Modules - DIMMs.

The motherboard’s three DIMM sockets accept DIMMs of up to 128 Mbytes in any combination (giving a maximum memory capacity of 384 Mbytes). The slot 'MM1' nearest to the processor  is recommended to be used first.

Note that the Lightning and Lightning BX motherboards use DIMMs of different specifications. See below for details and ensure that you fit the correct type.

The DIMMs you use must have the following specification: gold contacts, 3.3V, 64 or 72-bit, unbuffered, SDRAM-type with Serial Presence Detect (SPD) and a CAS latency of 2 at 66 MHz. If you use any other type of DIMM you risk damaging the motherboard.

Lightning BX
The DIMMs you use must meet the following specification:
Serial Presence Detect (SPD), gold contact, 64-bit, (or 72-bit ECC), unbuffered, 3.3V, SDRAM type, Intel PC100 spec compliant.

The ECC capabilities of 72-bit DIMMs will only operate if all the DIMMs in the system are 72-bit.

Using DIMMs of a different type could affect system performance with a risk of damaging the motherboard.


SDRAM memory expansion for Lightning Systems (LW, LG, LH, LK, LL)
16MB 64-bit DIMM Module XB61385
32MB 64-bit DIMM Module XB61386
64MB 64-bit DIMM Module XB61387
128MB 64-bit DIMM Module XB61388
SDRAM memory expansion for Lightning BX Systems (LB, LJ)
16MB 64-bit DIMM Module (PC100) XB64151
32MB 64-bit DIMM Module (PC100) XB64152
64MB 64-bit DIMM Module (PC100) XB64153
128MB 64-bit DIMM Module (PC100) XB64154
Video memory expansion for LS500 and LS600 Pentium II systems
2MB to 4MB SGRAM upgrade (Pentium II 233, 266, 300, 333MHz) XB61393
4MB to 8MB SGRAM upgrade (Pentium II 350, 400MHz) XB64155
Drive Options
2.1GB IDE Stratus hard disk drive add-in SU61670
3.2GB IDE Stratus hard disk drive add-in SU61671
4.3GB IDE Stratus hard disk drive add-in SU62667
IDE HDD fixing kit SU56129
CD-ROM Drives
IDE CDU-511 Sony x16 Speed PCAV CD-ROM Drive XB61060
IDE CDU-621 Sony x12-24 Speed PCAV CD-ROM Drive XB62488
IDE CDU-711 Sony x14-32 Speed PCAV CD-ROM Drive SU63831
IDE Sony CD-ROM Drive Fixing Kit for LS500 SU56017
IDE Sony CD-ROM Drive Fixing Kit for LS600 SU60353
SCSI card options
Adaptec 1510B SCSI card add-in (No HDD Support) SA50160
Adaptec 2940 PCI SCSI Card add-in UD55556
SCSI Fixing Kit for AHA1510 SU56213
SCSI Fixing Kit for AHA2940 SU56214
Connectivity options
Intel Pro 100B PCI Ethernet Card XB61343
3Com triple-combo Ethernet card (3C509B) XB55742
3Com 10/100 PCI Ethernet (3C905TX) XB59527
56K ISA Modem XB62192
Diamond ISDN Modem (64K) XB62494
3Com 8 port Micro Hub & 3 x 5M UTP cables XB62451
Specialix serial cards
32-port ISA SI/XIO serial card XB54693
4 port terminal adaptor XB43319
8 port terminal adaptor XB43320
8 port modular terminal adapter XB54611
8 port modular terminal adaptor (7 RS232, 1 Parallel) XB54612
Audio Options
Apricot Deepsound Subwoofer XB58090
20W Powered external speakers XB55607
Wavetable upgrade for on-board audio XB57690

Jumper Settings

There are only a few jumpers on the motherboard that you may need to alter. All others are set at the factory and should not be changed.

On the motherboard, pin 1 of each jumper block is indicated by a small triangular marking.

Do not change jumper settings unnecessarily
Do not alter any jumpers or switch settings other than those identified in this chapter, unless told to by your Mitsubishi Electric PC supplier or an authorised maintainer. Otherwise, you may damage the system processor, the motherboard, or both.

On-board video disabling (J1)
If you install a video adapter expansion card, the computer should automatically detect this and disable the on-board video adapter. If for some reason this does not happen, and you experience problems with a newly-fitted card, you can manually disable the on-board video adapter by moving jumper J1 from position 2-3 (EN) to position 1-2 (DIS).

Processor multiplier (J5 to J8)
The details below are given for the clock speeds of processors known at the time of writing. Higher speed and overdrive processors may become available, in which case consult your supplier for further information.

In the case of the Lightning BX, the processor will send information to the BIOS and the BX chipset, ensuring that the required bus frequency is set automatically.

You then have to set the links as below.

CPU bus speed
J5 J6 J7 J8 Ratio 66MHz bus 100MHz bus *
I I I O 3 200 -
O I I O 3.5 233 350
I I O I 4 266 400
O I O I 4.5 300 450
I I O O 5.0 333

I = jumper fitted, O = No jumper

* Lightning BX only

Audio DSP (J9)
If you need to disable the PCI audio accelerator (DSP) move jumper J9 from pins 1-2 (EN) to pins 2-3 (DIS).

Audio disabling (J10)
The on-board audio system can be disabled by removing jumper J10 from pins 1-2 (EN) to pins 2-3 (DIS). Disabling the audio system frees the interrupt and DMA channel used by that system (normally IRQ5 and DMA1).

BIOS upgrade and reprogram (J12, J2)
These jumpers should not normally be changed except by a service engineer or at the direction of a service engineer.

CMOS is cleared by moving the jumper J12 to the 2-3 (CLR) position for a few moments while the system is turned off and the power cord removed, then returning it to the 1-2 (NOR) position. It must be returned to normal before the power is reconnected.

BIOS reprogramming (J2) requires special software.

Clearing CMOS


CMOS battery connected (default)


CMOS battery disconnected


BIOS reprogramming






* This jumper must be returned to the normal position before reconnecting the power cord.

Fan Connectors, PL3 & PL2


CPU Fansink PL3


Main fan PL2






+ 12v


+ 12v (controlled)*


Fan Fail


Fan Fail

* This voltage varies to control the fan speed. This is determined from the processor’s heatsink temperature sensor.



Replacing the configuration battery

The computer keeps a record of its current hardware configuration in a CMOS memory chip which is sustained by a small battery. This battery has a life of up to 5 years. If you find that you have to reconfigure the computer every time you turn it on, the battery is probably failing and needs to be replaced.

The battery is a 3 volt lithium type (CR2032 or equivalent) typically used in calculators and other small, battery-powered electronic items.

To replace the battery

Turn off the computer and unplug all power cords.
Take suitable anti-static precautions and remove the right side panel.
Using a non-conductive implement, release the latch that holds the battery in place. The battery will pop up allowing you to lift it out of the holder.

You must not use a metal or other conductive implement to remove the battery. If a short-circuit is accidentally made between the battery’s positive and negative terminals, the battery may explode.

Check that the replacement battery looks the same as the battery you have removed.
Taking care not to touch the top or bottom surface of the battery, pick up the replacement with the positive (+) terminal upwards. Press the battery into the holder using a non-conductive implement.
Refit the right side panel.
Dispose of the discharged battery in accordance with the battery manufacturer’s instructions.
The next time you turn on the computer you will have to run the BIOS Setup utility to reset the hardware configuration.

System Resources

Components Interrupts (IRQs)
  0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
System timer                                
Keyboard controller                                
PIC daisy chain                                
Infra-red remote control BS                                
Serial port 1 BS                                
Audio JS                                
Diskette controller BS                                
Parallel port (usually sharable)                                
Real time clock                                
On-board video (sharable) JS                                
USB (sharable) BS                                
Mouse BS                                
Primary E-IDE BS                                
Secondary E-IDE BS                                


Components DMA channels
  0 1 2 3 4 5 6 7
Audio JS                
Diskette controller BS                
Parallel port (in ECP mode) BS                
DMAC daisy chain                


Fixed assignment BS = Can be disabled by BIOS Setup
Usual assignment JS = Can be disabled by changing a motherboard jumper setting
Alternative assignment by BIOS Setup
Alternative assignment by Plug-and-Play

POST Beep Codes


Beeps Test which failed


1-2-2-3 BIOS ROM checksum


1-3-1-1 DRAM refresh.


1-3-1-3 8742 keyboard controller

2C xxxx

1-3-4-1 RAM failure on address line xxxx.

2E xxxx

1-3-4-3 RAM failure on data bits xxxx of low byte of memory bus.

30 xxxx

1-4-1-1 RAM failure on data bits xxxx of high byte of memory bus.


2-1-2-3 Check ROM copyright notice


2-2-3-1 Test for unexpected interrupts


1-2 Video configuration failure, or option ROM checksum failure. (One long, two short beeps.)


Computing for a Connected World