My PC is not displaying anything, all I see is just blank screen but I hear the fan running and lights flash on keyboard and some beeps. What could be wrong? 

On startup, computers perform a Power-on Self Test, commonly referred to as a POST. If problems are found while booting, you can usually diagnose them using the error codes displayed on the screen. However, if nothing displays on the screen, the computer might use sounds (i.e., beep codes) to tell you what is wrong. Many of these errors indicate hardware problems that a service technician should fix. 

But on startup, if you see keyboard lights flash  for two times it does mean your computer motherboard is working good. If not you can very well diagnose the cause to be something wrong with the motherboard components.

Many BIOSes will have different beep codes even if they appear to be from the same manufacturer. This is because motherboard manufacturers reprogram codes to reflect their own customizations. You can often go to the web site for the motherboard’s manufacturer to find the updated codes, but you may find cases where the manufacturer simply does not document the changes.

 Award

Award BIOSes typically use more screen errors than beep codes.

For Award BIOSes manufactured by Phoenix Technologies, note the following from the Phoenix Technologies AwardBIOS Error Messages page: 

“The only AwardBIOS beep code indicates that a video error has occurred and the BIOS cannot initialize the video screen to display any additional information. This beep code consists of a single long beep followed by two short beeps. Any other beeps are probably RAM (Random Access Memory) problems.” 

Award BIOSes not manufactured under Phoenix Technologies use the following beeps; this information is from the BIOS Central Award BIOS Beep Codes page: 

Beeps Meaning

1 long, 2 short Video adapter error: Bad or improperly seated video card

Repeating beeps Memory error: Bad or improperly seated RAM 

1 long, 3 short Bad video RAM or video card not present 

High-frequency beeps Overheated CPU: Check fans 

Repeating high/low beeps CPU: Improperly seated or defective CPU 

AMI (American Megatrends) 

The information below is from the BIOS Central AMI BIOS Beep Codes page

 Beeps And What Do They Mean?

 1 short DRAM refresh failure

 2 short Parity circuit failure in the first 64KB of RAM: Likely a bad RAM IC, or possibly one of the hardware tests has failed 

3 short Memory failure in the first 64KB of RAM: Likely a bad RAM IC

4 short System timer failure: Bad clock IC or bad RAM in the first bank of memory 

5 short Processor failure: The CPU has failed. 

6 short Keyboard controller Gate A20 error: The keyboard controller has failed. Due to its integration into the system board, you usually must replace the motherboard. 

7 short Virtual mode exception error: CPU has generated an exception error; bad CPU or motherboard 

8 short Display memory Read/Write test failure: Bad video card

9 short ROM BIOS checksum failure: BIOS is defective 

10 short CMOS shutdown Read/Write error 

11 short Cache Memory error: Specifically, the L2 cache is bad. 

1 long, 2 short Video system failure: Error in video card BIOS, or a horizontal retrace has failed 

1 long, 3 short Conventional/Extended memory failure: RAM is bad 

1 long, 8 short Display/Retrace test failed: Video adapter is defective or missing 

AST BIOS 

The following information is from the BIOS Central AST BIOS Beep Codes page.

Beeps Meaning

1 short CPU register test failure: The CPU has failed.

2 short Keyboard controller buffer failure: The keyboard controller has failed. 

3 short Keyboard controller reset failure: The keyboard controller has failed or the motherboard circuitry is faulty. 

4 short Keyboard communication failure: Bad keyboard controller or keyboard 

5 short Keyboard input failure: The keyboard controller IC has failed. 

6 short System board chipset failure: The chipset on the motherboard has failed. Replace the motherboard. 

9 short BIOS ROM checksum error: The BIOS ROM has failed. If possible, replace the BIOS on the motherboard. 

10 short System timer test failure: The system clock IC has failed. 

11 short ASIC failure: Motherboard circuitry has failed. Replace the motherboard. 

12 short CMOS RAM shutdown register failure: The real-time clock/CMOS IC failed. Replace the CMOS or motherboard. 

1 long DMA controller 0 failure: The DMA controller IC for channel 0 has failed. If possible, replace the IC. 

1 long, 1 short DMA controller 1 failure: The DMA controller IC for channel 1 has failed. If possible, replace the IC. 

1 long, 2 short Video vertical retrace failure: The video adapter has probably failed. Replace the video adapter. 

1 long, 3 short Video memory test failure: The video adapter’s memory has failed. Replace the video adapter. 

1 long, 4 short Video adapter failure: The video adapter has failed. Replace the video adapter. 

1 long, 5 short 64KB memory failure: A failure has occurred in the base 64KB of memory. If possible, replace the RAM IC. 

1 long, 6 short Unable to load interrupt vectors: The BIOS was unable to load the interrupt vectors into memory. 

1 long, 7 short Unable to initialize video: This is a video problem. Replace the video adapter first. If the problem persists, replace the motherboard. 

1 long, 8 short Video memory failure: The is a failure in the video memory. Replace the video adapter first. If the problem persists, replace the motherboard. 

Compaq

The following information is from the BIOS Central Compaq BIOS Beep Codes page.

Beeps Meaning 

1 short No error: The system is booting properly. 

1 long, 1 short BIOS ROM checksum error: The contents of the BIOS ROM do not match the expected contents. If possible, reload the BIOS from the PAQ. 

2 short General error: No specifics available on what this code means 

1 long, 2 short Video error: Check the video adapter and make sure it’s seated properly. If possible, replace the video adapter. 

7 beeps (1 long, 1 short, 1 long, 1 short, pause, 1 long, 1 short, 1 short) AGP video: The AGP video card is faulty. Reseat the card or replace it outright. This beep pertains to Compaq Deskpro systems. 

Continuous beep Memory error: Bad RAM; replace and test 

1 short, 2 long Bad RAM: Reseat RAM, then retest; replace RAM if failure continues. 

Phoenix  

The following information applies to Phoenix BIOS Q3.07 or 4.x. This information is from the Phoenix BIOS beep codes section of the ComputerHope.com Computer POST/beep codes page. 

Dashes indicate pauses between beeps. 

Beeps Meaning 

1-1-1-3 Verify real mode. 

1-1-2-1 Get CPU type. 

1-1-2-3 Initialize system hardware. 

1-1-3-1 Initialize chipset registers with initial POST values.

1-1-3-2 Set in POST flag. 

1-1-3-3 Initialize CPU registers. 

1-1-4-1 Initialize cache to initial POST values. 

1-1-4-3 Initialize I/O. 

1-2-1-1 Initialize Power Management. 

1-2-1-2 Load alternate registers with initial POST values. 

1-2-1-3 Jump to UserPatch0. 

1-2-2-1 Initialize keyboard controller. 

1-2-2-3 BIOS ROM checksum 

1-2-3-1 8254 timer initialization 

1-2-3-3 8237 DMA controller initialization

1-2-4-1 Reset Programmable Interrupt Controller. 

1-3-1-1 Test DRAM refresh. 

1-3-1-3 Test 8742 Keyboard Controller. 

1-3-2-1 Set ES segment to register to 4 GB. 

1-3-3-1 28 Autosize DRAM. 

1-3-3-3 Clear 512KB base RAM. 

1-3-4-1 Test 512 base address lines. 

1-3-4-3 Test 512KB base memory. 

1-4-1-3 Test CPU bus-clock frequency. 

1-4-2-4 Reinitialize the chipset. 

1-4-3-1 Shadow system BIOS ROM. 

1-4-3-2 Reinitialize the cache. 

1-4-3-3 Autosize cache. 

1-4-4-1 Configure advanced chipset registers. 

1-4-4-2 Load alternate registers with CMOS values. 

2-1-1-1 Set Initial CPU speed. 

2-1-1-3 Initialize interrupt vectors. 

2-1-2-1 Initialize BIOS interrupts. 

2-1-2-3 Check ROM copyright notice. 

2-1-2-4 Initialize manager for PCI Options ROMs. 

2-1-3-1 Check video configuration against CMOS. 

2-1-3-2 Initialize PCI bus and devices. 

2-1-3-3 Initialize all video adapters in system. 

2-1-4-1 Shadow video BIOS ROM. 

2-1-4-3 Display copyright notice. 

2-2-1-1 Display CPU type and speed. 

2-2-1-3 Test keyboard. 

2-2-2-1 Set key click if enabled. 

2-2-2-3 56 Enable keyboard. 

2-2-3-1 Test for unexpected interrupts. 

2-2-3-3 Display message “Press F2 to enter SETUP”. 

2-2-4-1 Test RAM between 512 and 640KB. 

2-3-1-1 Test expanded memory. 

2-3-1-3 Test extended memory address lines. 

2-3-2-1 Jump to UserPatch1. 

2-3-2-3 Configure advanced cache registers. 

2-3-3-1 Enable external and CPU caches. 

2-3-3-3 Display external cache size. 

2-3-4-1 Display shadow message. 

2-3-4-3 Display non-disposable segments. 

2-4-1-1 Display error messages. 

2-4-1-3 Check for configuration errors. 

2-4-2-1 Test real-time clock. 

2-4-2-3 Check for keyboard errors. 

2-4-4-1 Set up hardware interrupts vectors. 

2-4-4-3 Test coprocessor if present. 

3-1-1-1 Disable onboard I/O ports. 

3-1-1-3 Detect and install external RS232 ports.

3-1-2-1 Detect and install external parallel ports. 

3-1-2-3 Re-initialize onboard I/O ports. 

3-1-3-1 Initialize BIOS Data Area. 

3-1-3-3 Initialize Extended BIOS Data Area. 

3-1-4-1 Initialize floppy controller. 

3-2-1-1 Initialize hard-disk controller. 

3-2-1-2 Initialize local-bus hard-disk controller. 

3-2-1-3 Jump to UserPatch2. 

3-2-2-1 Disable A20 address line. 

3-2-2-3 Clear huge ES segment register. 

3-2-3-1 Search for option ROMs. 

3-2-3-3 Shadow option ROMs. 

3-2-4-1 Set up Power Management. 

3-2-4-3 Enable hardware interrupts. 

3-3-1-1 Set time of day. 

3-3-1-3 Check key lock. 

3-3-3-1 Erase “F2″ message. 

3-3-3-3 Scan for F2 keystroke. 

3-3-4-1 Enter SETUP. 

3-3-4-3 Clear in-POST flag. 

3-4-1-1 Check for errors. 

3-4-1-3 POST complete; prepare to boot operating system. 

3-4-2-1 One beep. 

3-4-2-3 Check password (optional). 

3-4-3-1 Clear global descriptor table. 

3-4-4-1 Clear parity checkers. 

3-4-4-3 Clear screen (optional). 

3-4-4-4 Check virus and backup reminders. 

4-1-1-1 Try to boot with INT 19. 

4-2-1-1 Interrupt handler error. 

4-2-1-3 Unknown interrupt error. 

4-2-2-1 Pending interrupt error. 

4-2-2-3 Initialize option ROM error. 

4-2-3-1 Shutdown error. 

4-2-3-3 Extended Block Move. 

4-2-4-1 Shutdown 10 error. 

4-3-1-3 Initialize the chipset. 

4-3-1-4 Initialize refresh counter. 

4-3-2-1 Check for Forced Flash. 

4-3-2-2 Check HW status of ROM. 

4-3-2-3 BIOS ROM is OK. 

4-3-2-4 Do a complete RAM test. 

4-3-3-1 Do OEM initialization. 

4-3-3-2 Initialize interrupt controller. 

4-3-3-3 Read in bootstrap code. 

4-3-3-4 Initialize all vectors. 

4-3-4-1 Boot the Flash program. 

4-3-4-2 Initialize the boot device. 

4-3-4-3 Boot code was read OK 

IBM Desktop 

Beeps Meaning 

No beep No power, loose expansion card (ISA, PCI, or AGP), a short, or an improperly grounded motherboard 

1 short System OK 

1 long Video/display problem; video card incorrectly seated or defective 

2 short POST Error displayed on monitor 

3 long Problem with 3270 keyboard card 

1 long, 1 short Problem with system board 

1 long, 2 short Problem with display adapter (MDA, CGA) 

1 long, 3 short Problem with EGA 

Repeating short beeps Problem with power supply or system board 

Continuous beep Problem with power supply or system board 

IBM Thinkpad 

Beeps Message 

Continuous beeping System board failure 

1 beep with blank display LCD connector problem, LCD backlight inverter failure, video adapter failure, or LCD assembly failure 

1 beep w/message “Unable to access boot source” Boot device failure or bad system board 

1 long, 2 short System board, video adapter, or LCD assembly failure 

1 long, 4 short Low battery voltage

1 beep every second Low battery voltage 

2 short w/message Read the error message on the display 

2 short with blank display System board failure 

Mylex 

Beeps Meaning  

1 Normal boot: No problems 

2 Video adapter error: Video adapter is not seated or is faulty 

3 Keyboard controller error: Keyboard controller IC bad 

4 Keyboard error: Keyboard itself might be bad, or the controller IC on the motherboard 

5 PIC 0 error: The programmable interrupt controller IC is bad 

6 PIC 1 error: Same as above 

7 DMA page register error: DMA controller IC is bad 

8 RAM refresh error 

9 RAM data error

10 RAM parity error 

11 DMA controller 0 error: DMA controller IC for channel 0 has failed 

12 CMOS RAM error: Bad CMOS RAM 

13 DMA controller 1 error: DMA controller IC for channel 1 had failed 

14 CMOS RAM battery error: Dead CMOS battery; can usually be replaced 

15 CMOS RAM checksum error: CMOS RAM failed 

16 BIOS ROM checksum error: BIOS RAM failed 

Quadtel BIOS 

The following information is from the BIOS Central Quadtel BIOS Beep Codes page. 

1 short Normal boot: System is booting normally. 

2 short CMOS IC error: The CMOS RAM is faulty. Replace the IC if possible. 

1 long, 2 short Video failure: The video adapter is faulty. Reseat the video adapter or replace the adapter if possible. 

1 long, 3 short Peripheral controller error: One or more of the system peripheral controllers is bad. Replace the controllers and retest. 

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