HP omnibook xt1000 Service Manual

HP Pavilion zt1100/xz100 Omnibook xt1000 

Troubleshooting and Diagnostics 

3-25 

The POST (Power-On Self-Test) is a series of initialization routines and diagnostic tests that the 
system BIOS runs when the notebook boots. The system BIOS will not boot the operating system if 
system memory, the CPU, DMA, or interrupt controller fails the POST diagnostic tests. POST 
progress is indicated by a sequence of codes, and error messages are displayed if possible. 

You should not necessarily interpret the failure of one or more POST tests as a hardware, software, or 
firmware failure. If an error message appears, confirm the problem using other diagnostic tools. Not 
all POST messages indicate a hardware, software, or firmware failure—some messages are for 
information only. 

First, confirm the failure by performing a “clean” boot, as described below: If the notebook fails to 
restart with a clean boot, it requires repair. 

1. Remove all accessories, including SDRAM modules, PC cards, printer, external monitor, pointing 

device, and keyboard. 

2. Provide “clean” AC power—no auto adapter or unusual AC adapter configuration. 

3. Press the reset switch to return the notebook to a known state. 

If the BIOS detects a terminal error condition, it halts POST after issuing a terminal error beep code 
and/or displaying a message (see the following table). The beep code indicates the POST routine in 
which the terminal error occurred. 

If the system fails after you make changes using the BIOS configuration utility, reset the notebook, 
enter the BIOS configuration utility, and install the defaults or correct the error. 

5 short, 1 long 

FAULTY DMA PAGE REGISTERS 

DMA page registers do not function properly. 

4 short, 1 long, 
1 short 

FAULTY REFRESH CIRCUIT 

RAM refresh circuit does not function properly. 

4 short, 2 long 

ROM CHECKSUM INCORRECT 

BIOS ROM checksum failed. 

3 short; 1 long, 
2 short 

CMOS RAM TEST FAILED 

CMOS RAM test failed. 

3 short, 1 long, 
1 short, 1 long 

DMA CONTROLLER FAULTY 

DMA controller does not work properly. 

3 short; 2 long, 
1 short 

INTERRUPT CONTROLLER FAILED 

Interrupt controller does not work properly. 

3 short; 3 long 

(None) 

Keyboard controller failed to respond to the self-
test command. 

2 short, 1 long; 
3 short 

(None) 

No video device found. 

2 short, 1 long; 
2 short, 1 long 

(None) 

No RAM installed. 

(None) 

KEYBOARD CONTROLLER FAILURE 

Keyboard controller failed during system inquiry 
about connected devices. 

(None) 

KEYBOARD FAILURE 

Keyboard fails to respond or no keyboard is 
connected. 

(None) 

CMOS FAILURE - RUN SCU 

CMOS data error, probably due to loss of battery 

power. 

(None) 

CMOS CHECKSUM INVALID - RUN SCU 

CMOS checksum error.