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Commodore PC10-III, PC20-III, Colt, Select Edition

PC10-III Known Issues

PC10-III Rev 6 PCB Assembly - Expansion bus problems

Problems with third party hardware add-ons using PC10-III Rev 6 PCB assemblies (also used in PC20-III and Colt), have been traced to the "IOREADY" signal which will tri-state when it is not pulled low by PVC4.

A field fix has not been issued for this problem.
PCB# 312625-01 (marked Rev 6.2) are available for exchanges.
The normal PC warranty will cover the exchange.

Source: Commodore Techtopics 26/5-1.1

Auto-Config - Third party mouses

The PC10-III, PC20-III and Colt have a mouse port which is used by the Commodore 1352 mouse.

Third party mouse cards used in the expansion slots override the build in mouse driver when the system runs Auto-Config program during the power up sequence.

The Commodore mouse uses interrupt 2, this conflicts with certain third party mouses, such as Logitech, which also use interrupt 2.

A program is available from Service which disables Commodore mouse interrupt and allows the third party mouse to use interrupt 2.

Refer to CTOC section 7 Download, of current on-line issue 25 Techtopics for instructions.

CHGMOUSE - is the program file.
README - file contains information on the program.

Source: Commodore Techtopics 24/5-1.1

PC10-III Upgrades

BIOS 4.38

A new BIOS ROM, revision 4.38, CBM part number - 318085-05, has been released for the PC10-III, PC20-III, Colt and the Select Edition.

This is considered a running change, and is not covered by warranty. Customers must pay for this upgrade. Dealer billing is $33.00.

The new ROM rev 4.38 adds a new setup feature which emulates the "AT" setup utility. To run the "AT" setup utility, press <Cntrl-Alt-Esc>. The screen resembles the PC40-III setup.

Default configuration is:

BIOS revision 4.38 supports the 5720 IO/mouse controller, and real time clock access - like "AT" systems, clock is set during setup, the setclock utility does not need to be run.

Source: Commodore Techtopics 28/5-2.1

BIOS 4.36

A new BIOS ROM for the PC10-III, PC20-III and Colt is being released. New part number is 318085-02. This is an in-line upgrade and must be purchased by the end user directly through an authorized service center. Installation of this IC must be done by an Commodore authorized technician.

The following summary details changes in BIOS 4.36

  1. 9600 baud problem
    Terminal and communications software packages which used interrupt-driven COM:, dropped characters.
    Fix: code intended to simulate keyclick corrected.
  2. Equipment check
    BIOS INT 11H return 40 column status when in 80 column mode and 80 column status when in 40 columns mode when running in CGA mode.
    Fix: BIOS modified to return correct color mode number.
  3. F11 and F12 keys
    BIOS INT 16H returns incorrect scan codes for function keys F11 and F12
    Fix: keyboard table was correced.
  4. New Microsoft bus mouse
    BIOS AutoConfig™ did not recognize newest Microsoft bus mouse. Result incorrect operation of entire system.
    Fix: BIOS now tests for either type of mouse before enabling onboard mouse.
  5. EGA board problems
    Several EGA cards exhibited memory conflicts with PVC4 controller.
    Fix: PVC4 video controller will be disabled if a special video adapter BIOS module (EGA, VGA, etc.) is found.
  6. IBM3270 card
    IBM 3270 cards did not function
    Fix: patch code in INT 1A.
  7. HD boot speed
    Hard drive takes to long to boot.
    Fix: latest BIOS improves load time.
  8. IBM 5250 card
    Upload, download problems with 5250 emulator to IBM system 38.
    Fix: patch code in INT 1A.
  9. OKI real-time clock chip problems
    RTC register altered by unauthorized system code.
    Fix: RTC initialization code modified.
  10. Cold boot from S/W
    Programs which issue a call to the BIOS cold boot location (F000:E05B) or the hardware reset vector (FFFF:0000) will hang (example - MSDOS FDISK).
    Fix: Cold and warm boot code modified.
  11. System crash
    Unexpected interrupt causes system to crash or hang up after prolonged use.
    Fix: Modified unexpected interrupt code.
  12. Enhancement of onboard base memory configuration
    If offboard memory is found from 0k to 640k the corresponding onboard memory bank is disabled. If no offboard memory is found, then onboard memory is configured to 640k.

Source: Commodore Techtopics 22/5-3.1

PC10-III Firmware

CBM 8088 Monitor

The PC10-III, PC20-III and Colt have a built in monitor, in addition to the debug monitor in the operating system.

The Commodore 8088 Monitor may be entered when a error condition is detected on power up tests by pressing the control key in combination with the 'M' key.

You may examine the monitor by leaving the boot disk out of system at power up, a system message will appear on console:
Boot disk failure. Type key to retry

Press Cntrl + M to enter CBM monitor.
System will respond with:

COMMODORE 8088 Monitor
Pre-release Version 2.0
Copyright 1987 Commodore Technology Group
Use ? for help

Responding with a question mark, return, will generate the following monitor options:

Dump [starting addr]
Fill [starting addr] [count] [data]
Goto [addr] [breakpoint1] [breakpoint2]
Input port [byte|word] [port addr]
Output port [byte|word] [port addr] [data]
iNterrupt [#hex]
Move [source addr] [dest addr] [count]
Substitute Memory [address]
eXamine [register]

Source: Commodore Techtopics 22/5-2.1

PC10-III Parts List

Integrated Circuits
PositionDescriptionPart number
U1028088 10MHz380200-02
U104, U204, U205, U30474LS245901521-46
U108, U109, U202, U60374LS244901521-03
U4041488 Driver901882-01
U4051489 Receiver901883-01
U601PVC4 Video318088-01
U602Custom 5720318097-01
U605, U321..U32464k x 4 DRAMs 100 ns390083-04
U305..U320256k x 1 DRAMs 80 ns390223-05
U607Video Character ROM318086-01
U201BIOS ROM318085-01

Source: Service Manual PC 10-1/10-2/10-III PN-314860-01 March, 1988 © 1988 Commodore Electronics Limited

PC10-III Memory Map

Memory Map
Memory Address (Hex)Contents
00 00 0003 FF FF640k base RAM
04 00 0009 FF FF
0A 00 000A FF FFEGA/VGA video RAM
0B 00 000B 3F FFMonochrome video
0B 40 000B 7F FFReserved
0B 80 000B FF FFColor video
0C 00 000C 7F FFReserved for EGA BIOS
0C 80 000C 9F FFAvailable
0C A0 000F 7F FFReserved
0F 80 000F 9F FFCBM 8088 Monitor
0F A0 000F BF FFHard Drive BIOS
0F C0 000F FF FF16k Main BIOS

Source: Commodore Techtopics 22/5-1.1

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Last update: 26 March 2021