Troubleshooting and Repair 3-5
BEEP CODES
Beep codes are used to identify a POST error that occurs when the screen is not available.
Once the screen is operating, diagnostic messages are reported to the screen. There are
beep codes for both fatal and non-fatal system board errors.
NOTE:
No beep code is generated if a test is
aborted while in progress. However, diagnostic
cards can be installed in order to display the
contents of the diagnostic port 80h and identify
the area of failure.
Explanation of Test Terms for Beep Code Table
The following terms are used in the Test Performed column of the beep code table.
1.
Pattern test - One or more particular patterns are written to a location then read
back from the same location. Examples of patterns used are 55h and AAh. If the
value read does not match the value written, the test is considered a failure.
2.
Rolling ones test - Several patterns are constructed. These patterns represent a
one rolling through the given location. For example, to roll a one through three
bits, the following patterns would be constructed: 001, 010, 011, 100, 101, 110,
and 111. The patterns are written to the location and then read back, one by one.
If the value read does not match the value written, the test is considered a failure.
3.
Rolling zeros test - Several patterns are constructed. These patterns represent a
zero rolling through the given location. For example, to roll a zero through three
bits, the following patterns would be constructed: 011, 001, and 000. The patterns
are written to the location and then read back, one by one. If the value read does
not match the value written, the test is considered a failure.
4.
Checksum test - All of the values in a given range of locations are added to-
gether. The range includes a location which when added to sum of the ranges, will
produce a known result, such as zero.
