Epson 10020 - Manual (Page 183)

The computer spins the diskette for a few seconds then displays
a message like this:
The disk rotation speed is now 300.0 rpm.
Note
The speed for a 360KB or 720KB drive should be 300 rpm.
This check permits a tolerance of ±2%.
The diskette continues to spin, and the display is updated every
few seconds. To stop the test, press any key; the program returns
to the menu.
If you try to perform a speed test without inserting a diskette, or
if a read error occurs, you see this message and prompt:
Disk is defective or not installed properly.
Press ENTER to return to the menu.
Run All Above Checks
To run all the tests on the menu in sequence, press 5 and then
Enter. When you choose this option, all checks for the diskette
in drive d and the controller are performed automatically in
sequential order. Although you do not start each test, you must
still supply the appropriate responses to progress from one test
to the next.
Math Coprocessor Check (8087-1)
Use this option to check the operation of the 8087-1, 10 MHz
math coprocessor if you have installed one in your computer.
To check the math coprocessor, select option 7 from the
DEVICE LIST.
D-26 Performing System Diagnostics