?IO ERROR
Tandy / Radio Shack TRS-80
Severity: ModerateWhat it means
?IO ERROR on the TRS-80 means an input/output operation to cassette tape or floppy disk failed.
The most common causes are a dirty tape head, misaligned volume, or a bad floppy disk.
Clean the tape head and try again, or try a different disk.
Affected Models
- TRS-80 Model I
- TRS-80 Model II
- TRS-80 Model III
- TRS-80 Model 4
- TRS-80 Color Computer (CoCo)
- MAME TRS-80 emulator
- trs80gp emulator
Common Causes
- Cassette tape unreadable — dirty head or worn tape
- Cassette player volume too high or too low
- Floppy disk damaged, unformatted, or incompatible format
- Drive door not closed (on 5.25-inch drives)
- Trying to write to a write-protected disk or tape
How to Fix It
-
For cassette: clean the tape head and adjust the volume.
Use a cotton bud with isopropyl alcohol on the tape head.
Set volume to about 60-75% — too loud distorts the signal, too quiet loses it. -
For floppy disk: check the disk is inserted correctly and the door is closed.
On 5.25-inch drives, the latch must be down.
Try a different disk to rule out a bad disk vs a bad drive. -
Check for write protection if you are trying to SAVE.
Cassettes: check the write-protect tabs on the top of the cassette.
Floppy disks: check the write-protect notch on the disk edge. -
Rewind the tape fully and try loading again.
The TRS-80 searches the tape for a program header.
If the tape is not at the right position, loading fails.
Frequently Asked Questions
Did the TRS-80 Model II use cassette tapes?
No.
The Model II was a business machine with a built-in 8-inch floppy disk drive.
It never supported cassette tape storage — it was designed for serious business use from the start.
Can I load TRS-80 programs from a modern computer?
Yes.
You can play .CAS audio files from a phone or computer through a cable into the TRS-80's cassette port.
For disk-based models, devices like the FreHD or GoTEK can replace the floppy drive entirely.