Epson 10020 - Manual (Page 156)

RAM Check
The computer now begins to check the RAM installed on the
main system board and any option cards. During the check, you
see this message:
nnn KB OK
where nnn indicates the amount of memory in which no
malfunction is found. This value increases continuously by
64KB up to the amount of RAM installed on the main board,
which is 640KB. If the computer detects an error in the first
64KB area, it displays an error message and halts with no
further information.
If there are faulty RAM chips in your system,
you
see this
message:
nnnn0 201-Memory error
Give the error message and number to your Customer Care
Center.
Keyboard Controller and Keyboard Check
Next, the computer checks the keyboard controller and
keyboard for problems such as failure of one of the keys to
release. If there are any errors in the connection between the
keyboard and the computer, you see this error message:
301-Keyboard error
When a number precedes this message, the number represents
the key (in hexadecimal) that is causing the error. This
message may occur after you have used Ctrl Alt Del to reset the
computer, and does not necessarily indicate a problem.
Power-on Diagnostics C-3