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IBM 5150  -  POST  -  Some errors


POST = Power-On Self Test


IMPORTANT:  The following is specific to the IBM 5150 (IBM PC).
  Certain portions will not be applicable to clones that were made of the IBM 5150.


Error      Description
[ Nothing ]
There a few motherboard tests that the POST does early, and if they fail, the POST simply halts the CPU.
This is unfortunate, because it results in the 'motherboard appears to be dead' symptom, a symptom that has many causes.

In the 5150, one of these early POST tests is a test of the first 16K of RAM.

If you believe that your motherboard is starting, and that one of the early POST tests is failing, then I advise you to try the Supersoft/Landmark diagnostic ROMs.
Note however, that there is no point in trying the Supersoft/Landmark diagnostic ROMs if the power supply outputs (
voltage and POWER GOOD signal) are incorrect.
 
1 long beep then 1 short beep
Two causes:
• The POST's test of the motherboard's 8259 chip (includes supporting chips) failed.
• The POST's test of the motherboard's 8253 chip (includes supporting chips) failed.
 
1 long beep then 2 short beeps
Some causes:
• 5150 motherboard - Configured via SW1 for an MDA video card, but either the POST cannot find an MDA video card to initialise, or the MDA card is faulty.
• 5150 motherboard - Configured via SW1 for an CGA video card, but either the POST cannot find an CGA video card to initialise, or the CGA card is faulty.
• A video card with a BIOS expansion ROM did a self test and found a problem with itself.
• A bug in the 5150's POST - see description of 'C800 ROM' below.
 
1 long beep then 3 short beeps
The BIOS expansion ROM on an IBM EGA card is known to generate this if it discovers that the card has faulty RAM.
 
131  displayed on-screen
Failure of cassette port wrap-around (loopback) test.

Some possible 131 causes:
• 5150 motherboard of type 64KB-256KB is not receiving minus 5 volts.
   - Try reseating plug P9 from power supply, in case of bad connection.
   - Perhaps in use is an ATX power supply (via adapter) that does not have a minus 5 volts output.
• Motherboard relay K1 (cassette relay) is stuck in the 'motor on' position (indicated by zero, or low, resistance between pins 1 and 3 of the cassette DIN connector).
 
201   displayed on-screen

(xxxx  201)

RAM related error.
For the 5150, the 201 will be prefixed by a 2 bytes (e.g. "0410 201").

Some possible 201 causes:
• 5150 motherboard - RAM failure.
• 5150 motherboard - incorrect switch settings.
• 5150 motherboard - 10/27/82 BIOS fitted and less than 4 banks of RAM fitted.
• RAM expansion card - failure of its RAM or circuitry.
• RAM expansion card - incorrect switch settings.

More information at here
 
301   displayed on-screen

(301)
(xx  301)

Keyboard related error.

If the "301" is preceeded by a byte, e.g. "23 301", then the keyboard's self test is indicating to the POST that a key is 'stuck' down. The byte indicates which key (see here).

If the "301" is not preceeded by a byte, then it's a general keyboard error.
Possible causes:
• AT class keyboard attached. That will not work. A PC/XT class keyboard is required.
• Keyboard accidentally attached to cassette connector instead of keyboard connector.
• No keyboard attached.
• Faulty keyboard - broken wire in cable.
• Faulty keyboard - wire loose in connector.
• Faulty keyboard - chip failure.
• Faulty motherboard - bad solder joint on keyboard connector.
• Faulty motherboard - faulty keyboard circuitry.
 
601   displayed on-screen
Test of floppy drive 0 (DOS refers to this as A:) failed.

Some possible 601 causes:
• Floppy controller card - faulty.
• Floppy controller card - dirty edge connectors.
• Floppy cable - faulty.
• Floppy cable - not the correct type for a 5150 - see here.
• Floppy cable - not fitted correctly.
• Floppy drive - faulty.
• Floppy drive - drive select jumper not set properly - see here.
• Floppy drive - not configured correctly for a 5150.
 
1701   displayed on-screen
This error is not generated by the motherboard's POST, but by the initialisation code within a BIOS expansion ROM residing on an XT-class hard disk controller.

The maker of the particular XT-class hard disk controller decides in which situations they have their controller display the "1701" error.

1701 is typically a very high level error, indicating a problem with the hard drive system  (system = controller + cables + drive + configuration + power).
So, lots of possible causes.
See here for some ideas.
 
1801   displayed on-screen
The POST found an extender card for the IBM 5161 Expansion Unit within the 5150.
Because of that, the POST made an assumption that a 5161 Expansion Unit is connected to the card.
The POST attempted to communicate with the 5161 and that communication failed.

Some possible 1801 causes:
• 5161 Expansion Unit is not connected to the extender card.
• 5161 Expansion Unit not powered on (needs to be powered on before the 5150 is).
• Faulty extender card.
• Faulty cable.
• Faulty 5161 Expansion Unit.
 
C800 ROM   displayed on-screen
An expansion card has a BIOS expansion ROM addressed at C8000, and that ROM is faulty or corrupt.
C8000 is commonly used by XT-class hard disk controllers.

Because of a bug in the 5150's POST, you will never see this error.  Instead, you hear the '1 long beep then 2 short beeps' error, leading you to believe that a video problem exists.
 
CA00 ROM   displayed on-screen
An expansion card has a BIOS expansion ROM addressed at CA000, and that ROM is faulty or corrupt.
CA000 is commonly used by third-party floppy controllers (those that have a BIOS expansion ROM).
 
D000 ROM   displayed on-screen
An expansion card has a BIOS expansion ROM addressed at D0000, and that ROM is faulty or corrupt.
 
F600 ROM   displayed on-screen
Motherboard ROM chip U29 (contains part of Cassette BASIC) is missing or faulty or corrupt.       INFO: Only the 10/27/82 BIOS generates this error.
 
F800 ROM   displayed on-screen
Motherboard ROM chip U30 (contains part of Cassette BASIC) is missing or faulty or corrupt.       INFO: Only the 10/27/82 BIOS generates this error.
 
FA00 ROM   displayed on-screen
Motherboard ROM chip U31 (contains part of Cassette BASIC) is missing or faulty or corrupt.       INFO: Only the 10/27/82 BIOS generates this error.
 
FC00 ROM   displayed on-screen
Motherboard ROM chip U32 (contains part of Cassette BASIC) is missing or faulty or corrupt.       INFO: Only the 10/27/82 BIOS generates this error.