When power is first applied to the system, the POST BIOS code checks the
CPU, Keyboard, and various controllers and when it encounters an error, it
typically beeps and displays an error code and a brief message.

The earliest PCs, Xt, and ATs displayed a simple error code number and
left you wondering what happened.  Later BIOSes provide more info, but
often use the same numbering convention as shown below.

  Beep Codes  
No beeps, no display:        Power failure
Continuous beeps:            Power failure
Repeating short beeps:       Power failure
One short beep:              Display failure
One long, two short beeps:   Display failure
One long, three short beeps: EGA display failure

  100s: Motherboard  
101     Interrupt failure
102     Timer failure
103     Timer interrupt failure
104     Protected mode failure
107     Hot non-maskable interrupt (NMI) test
108     Timer bus test failure
109     Direct Memory Access (DMA) failure
110     Motherboard memory
111     Adapter memory
112,113,166  Adapter in system unit
121     Hardware interrupts
151     Defective battery
152     Real-time clock
161     Battery failure
162,165,199 System options not set correctly; run setup
163     Time and date not set correctly
164     Memory size error

  200s: Memory  
xxyyy yyzz 201 Bad Chip (note: code IDs chip, but differs for
various BIOSes, makes, and models
201,202 Memory test failed
203,215 Memory address error
216     Motherboard memory

  300s: Keyboard Errors  
301     Improper keyboard response or stuck key
302     User-indicated error from keyboard test or AT keylock locked
303     Keyboard or system
341     Replace keyboard
342     Replace interface cable
343     replace enhancement card or cable

  400s: Monochrome Monitor  
401     MDA video memory, horizontal sync, or video test failed
408,416,424  User-indicated display attributes failure
432     Parallel port test failed

  500s: Color Monitor  
501     Video memory, horizontal sync, or video test failed
408,516,424,532,540,548  User-indicated attribute or mode failure

  600s: Diskette Drive  
601     Diskette power-on diagnostics failed
602     Boot record not valid
603     Diskette size error
606     Diskette verify
607     Write protected
608     Bad command diskette status
610     Diskette initialization
611     Time out
612     Bad controller
613,614 Direct memory access (DMA)
621     Bad seek
622     Bad cyclic redundancy (CRC)
623     Record not found
624     Bad address mark
625     Bad controller seek
626     Diskette data compare
627     Diskette change line
628     Diskette removed

  600s: Math Coprocessor  
701     Coprocessor test failed

  900s: Parallel Printer Adapter LPT1  
901     Parallel printer adapter failure

  1000s: Parallel Printer Adapter LPT2  
1001    Alternate Parallel printer adapter failure

  1400s: Printer  
1401    Printer test failed
1404    Dot Matrix printer test failed

  1700s: Hard Disk  
1702    Time out error
1703    Seek error
1704    Disk adapter error
1705    No record found
1706    Write fault error
1707    Track 0 error
1708    Head select error
1709    Defective error check
1710    Read buffer overrun
1711    Bad address mark
1712    Undetermined error
1713    Data compare error
1714    Drive not ready
1780,1790 Disk 1 failure or error
1781,1791 Disk 2 failure or error
1782    Disk adapter error

See Also: POST
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Power-On Error Codes