IBM Personal Computer AT Manual To Operations page 273

t64-Memory Size Error-(Run SETUP).
To correct go to step 10, "Running the Setup
Program" and enter the correct memory size.
20t-Error System Unit.
To correct have your system unit serviced. Be
sure your Key Lock key is with your system
unit.
164 and 201 error combination is corrected as
follows:
1. First, go to step 10, "Running the Setup
Program" to verify that your memory size is
correct. If your memory size is correct, then
2. Refer to your Installation and Setup manual if
you installed a :
• 256KB Memory Module Kit and verify
that is is installed properly. After
checking for proper installation, go to
step 10 again to run "Setup".
• 512KB Memory Expansion option to
check the switch settings on the adapters
for proper memory size. After checking
the switch settings, go to step 10 again to
run "Setup".
3.
If
you cannot correct the error, have your
system unit serviced. Be sure your Key Lock
key is with your system unit.
Setup Errors 2 - 2 9