IBM xSeries 380, Hardware Maintenance Manual

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Hardware Maintenance Manual: xSeries 380
Run the Test Select Memory from the Main Menu and Parity Test. Press <Enter> to
start the Parity Test. A list of parameters appears, as shown below:
You can specify the beginning and ending memory locations in the Memory Start and
Memory End fields. You can also specify the size of the bit pattern written to memory
in this test in the Pattern Size field. By changing the bit pattern size, otherwise
undetected memory errors will be discovered. You should change this parameter to
ALL to perform the most thorough memory error detection test. The bit pattern sizes
are 8 bits, 16 bits, 32 bits, or all bit pattern sizes. The default is 32 bits.
The amount of memory already tested is displayed as the test runs. If the displayed
percentage is less than 100%, the displayed percentage is the amount of system
memory between the Memory Start and Memory End values.
Pattern test
This test is the most exhaustive memory test in AMIDiag. This test consists of seven
test routines that write a series of test patterns to memory, then read the patterns back
and compare the read results with the pattern that was written. This test uses worst-
case bit patterns, such as AA55h. The memory reads and write instructions test every
bit of DRAM system memory.
Test Description Each memory chip in your computer is designed to hold 1, 4, or 9
bits of data. If the memory chip does not retain data, there is an inconsistency in the
data written to and read from memory. For example, the hexadecimal number 11 can
be written to a memory location. If the chip that holds the least significant bit (bit 0) of
this number is faulty, 10 hex is read from memory instead of 11 hex. This is called bit
dropping. If bit 0 of this location sets a bit instead of dropping it, the system may read
11 hex when the actual data was 10h. If a program is loaded to the faulty memory
location, it either fails or produces erroneous results. If data is loaded into this
memory area, the data becomes corrupted.
When to Use The Pattern Test is most useful when the computer has random
memory (or performance) problems and BIOS POST tests cannot find memory
problems. If the system has random problems you cannot identify, run the Pattern
Test for several passes or even continuously. This rigorous memory test runs for a
long time, but when it is difficult to determine exactly where the error is, the test must
be extremely thorough. This test performs a long read and write test of memory space
and identifies most memory faults. The diagnostic routines in the pattern test find
system memory problems. These tests can run for an hour, depending on the CPU
type and the amount of system memory. A picture of memory appears. Test progress
is shown by flashing each tested memory segment as the test runs on that segment.