I purchased a vintage Apple IIc computer and I want to make sure there are no failing components. I booted up the computer while pressing both Apple keys (open and close) at the same time. The computer went into the self-test mode:

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However, this test has been running for more than 2 hours now. It has been decades since I have used one of these machines, so I am not sure if this is to be expected, or if the long run time is an indication of some issue.

Does anyone know how long this test should run?

Also, do I need to have a blank floppy disk in the internal drive in order for it to test the drive as well?

  • 2
    With regret, I will comply with the OP’s request to move a perfectly fine question for here to another site. I would hate to have it cross posted and if it gets a better answer there - we all win.
    – bmike
    Commented May 22, 2020 at 19:11
  • @bmike I guess there are plenty of old Apple II guys on Ask Different, so it would have fitted nicely over there.
    – Raffzahn
    Commented May 23, 2020 at 3:39
  • Oh, I see this question is related to your other one. I think the self-test behaviour you're seeing might be that of a ROM 255 //c. Commented May 23, 2020 at 4:04

2 Answers 2


34 seconds or forever, depending on the ROM version. (Find your version here.)

You can start the self-test at any time with: Ctrl+Open Apple+Closed Apple+Reset

The ROM 255 self-test is a "memory and soft switch exercise program" that will appear to hang (forever) on a screen of garbage. Here is one of the various results I got using the MAME emulator. It looks similar to your screen:

Apple IIc screen of "garbage"

For the other ROM versions the self-tests complete in around 34 seconds and show "System OK" if there's no problem, or diagnostic information otherwise. I tested them all with MAME:

| Machine           | ?PEEK(64447) | Self Test | Time | OK Result |
| Apple //c ROM 255 | 255          | No        | N/A  | N/A       |
| Apple //c ROM 0   | 0            | Yes       | 34s  | System OK |
| Apple //c ROM 3   | 3            | Yes       | 34s  | System OK |
| Apple //c ROM 4   | 4            | Yes       | 34s  | System OK |
| Apple //c Plus    | 5            | Yes       | 34s  | System OK |

The self-test doesn't test any disk drive functionality.

  • Does the ROM-255 self-test "not work", or is it simply designed to run until failure? Depending upon what one is trying to test, a run-until-failure diagnostic may find problems that might not manifest themselves during a 34-second self-test.
    – supercat
    Commented Apr 26, 2021 at 21:04
  • @supercat: It runs forever. Firmware source code for the routine is on page 155 of the The Apple //c Reference Manual Volume 2. It's prefixed by this comment: "The following code Is Teri's memory and soft switch exercise program. The only purpose is exercise, not diagnostic functions. This code is activated on a system without a keyboard, or when both open and closed apple keys are pressed during the reset sequence." Commented Apr 27, 2021 at 6:14

Not all IIc models do have the self test ROM. But if they do, it for sure doesn't run for hours. The most reliable way to invoke it is from reset.

  1. Power on
  2. Hold down Open-Apple+CTRL and then press RESET
  3. Release
  4. Wait for a ] to show up as BASIC prompt
  5. Hold down Open-Apple+Closed-Apple+CTRL and then press RESET
  6. Release the RESET key
  7. Release the rest
  8. Now self-test should kick in
  • 1
    I concur, it doesn't run for hours. My memory is a little vague, but pretty sure it only ran in the order of minutes (certainly less than a half hour).
    – Monomeeth
    Commented May 23, 2020 at 3:32
  • @Monomeeth Mine runs approx. 35 seconds until "System OK".
    – tofro
    Commented Oct 31, 2023 at 8:01

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