Hardware Reference
In-Depth Information
a known-good spare.
If you get this far, the problem is most likely either the motherboard or the power supply—or possibly
some other component in the system. Remove other components from the system to see whether they
are causing problems. Reseat the CPU, and replace the power supply with a high-quality new unit or
a known-good spare. Finally, try replacing the motherboard.
The system locks up frequently and sometimes reboots on its own.
This is one of the classic symptoms of a power supply problem. The power supply is designed to
send a special Power_Good signal to the motherboard when it has passed its own internal tests and
outputs are stable. If this signal is dropped, even for an instant, the system resets. Problems with the
power good circuit cause lockups and spontaneous rebooting. This can also be caused if the power at
the wall outlet is not correct. Verify the power supply output with a digital multimeter—all outputs
should be within 5% of the rated voltages. Use a tester for the wall outlet to ensure that it is properly
wired, and verify that the voltage is near 120V. Replace the power cord or power strip between the
power supply and wall outlet.
Unfortunately, the intermittent nature makes this problem hard to solve. If the problem is not with the
wall outlet power, the best recourse is to replace the power supply with a high-quality new unit or a
known-good spare of sufficient rating to handle the system (300 watts or higher recommended). If this
doesn't help, reseat the CPU and reinstall the heatsink with new thermal interface material. Then
reseat the memory modules, run only one bank of memory, and finally replace the motherboard.
I installed a larger hard disk drive in my system, but the system only sees 8.4GB or 137GB.
Motherboard ROM BIOSs have been updated throughout the years to support larger and larger drives.
BIOSs older than August 1994 are typically limited to drives of up to 528MB, whereas BIOSs older
than January 1998 are limited to 8.4GB. Most BIOSs dated 1998 or newer support drives up to
137GB, and those dated September 2002 or newer should support drives larger than 137GB. These
are only general guidelines; to accurately determine this for a specific system, you should check with
your motherboard manufacturer.
Tip
To determine whether your system supports the Enhanced Disk Drive (EDD) specification, the
BIOS date of your system, and hundreds of other facts about your computer hardware,
operating system, and software, use the System Information for Windows (SIW) utility from
If your BIOS does not support EDD (drives larger than 8.4GB), visit your motherboard
manufacturer's website to see whether it has any newer BIOSs available for your motherboard that
will support large drives. If you cannot get a BIOS update from your motherboard vendor, go to
eSupport.com and use its BIOSAgentPlus service to determine if a replacement flash BIOS is
available for your system.
The 137GB barrier is a bit more complicated because, in addition to BIOS issues, operating system
and chipset-based ATA host adapter driver issues are involved. Drives larger than 137GB are
accessed using 48-bit logical block address (LBA) numbers, which require BIOS support, chipset
driver support, and operating system support. Generally, you need a BIOS with 48-bit LBA support
