PC Diagnostics, Testing, and Maintenance - Upgrading and Repairing PCs - page 1234

POST checkpoint codes can track the system's progress through the boot process from
power-on right up to the point at which the bootstrap loader runs (when the operating sys-
tem load begins). When you plug a POST code reader card into a slot, during the POST
youseetwo-digithexadecimalnumbersflashonthecard'sdisplay.Ifthesystemstopsun-
expectedly or hangs, you can identify the test that was in progress during the hang from
the two-digit code. This step usually helps to identify the malfunctioning component.
Originally, most POST reader cards plugged into the 8-bit connector that is a part of the
ISA or Enhanced Industry Standard Architecture (EISA) bus. Some older PCI-based sys-
tems do still have ISA connectors that can use these cards. However, the motherboards
foundinmodernPCshavenoISAslots,soobviouslyanISAPOSTcardwon'twork.For-
tunately, the companies that make POST cards more often than not make PCI versions.
Micro 2000 has a card called the Post-Probe, which has both ISA and PCI connectors on
the same board. PC Diag Inc. has a similar card called the PCISA FlipPOST (see Figure
20.1 ) .
Figure 20.1 The PC Diag Inc PCISA FlipPOST diagnostics card works with both PCI- and ISA-based sys-
tems, and it also tests motherboard voltage levels.
AMI markets a USB-based diagnostic device called the AMIDebug RX to display check-
point and error codes for its AMIBios and Aptio 4.x firmware.
Although rare at this point, older Compaq and EISA-based systems from any vendor
might use an I/O port address other than port 80. Simpler POST cards monitor only port
80, but some cards have DIP switches or jumper blocks to configure the card to monitor
the different I/O port addresses these systems used.