Compaq AlphaServer ES45 Service Manual page 147

Use the show memory command or an info 0 command to see where
memory is located.
Starting address
Length of the section to test in bytes
Passcount. In this example, the test will run for 10 passes.
The test detected a failure on DIMM 3, which is located on MMB 2.
Use the show_status command to display the progress of the test. Use the kill
or kill_diags command to terminate the test.
Memtest provides a graycode memory test. The test writes to memory and
then reads the previously written value for comparison. The section of memory
that is tested has its data destroyed. The -z option allows testing outside of the
main memory pool. Use caution because this option can overwrite the console.
Memtest may be run on any specified address. If the -z option is not included
(default), the address is verified and allocated from the firmware's memory
zone. If the -z qualifier is included, the test is started without verification of the
starting address.
When a starting address is specified, the memory is allocated beginning at the
starting address -32 bytes for the length specified. The extra 32 bytes that are
allocated are reserved for the allocation header information. Therefore, if a
starting address of 0xa00000 and a length of 0x100000 is requested, the area
from 0x9fffe0 through 0xb00000 is reserved. This may be confusing if you try to
begin two memtest processes simultaneously with one beginning at 0xa00000
for a length of 0x100000 and the other at 0xb00000 for a length of 0x100000.
The second memtest process will send a message that it is "Unable to allocate
memory of length 100000 at starting address b00000." Instead, the second
process should use the starting address of 0xb00020.
SRM Console Diagnostics 4-45