Why didn't the GQ-4x4 misread when retested?

The GQ-4x4 read every test chip bit-perfect across twenty-eight sequential reads on two USB ports, with and without an inline USB tester, on fresh and aged chips. None of the variables tested reproduced the Part 1 failure. Intermittent EPROM read faults can stop reproducing when conditions shift between sessions — that's the nature of the failure mode.

Does an intermittent EPROM read fault mean the chip is bad?

Not necessarily. An EPROM verify error tells you the programmer's readback disagrees with its buffer. The disagreement can be a bad chip, an incomplete burn, or the programmer misreading a good chip. Compare the chip against the original source file with a tool independent of the programmer — DOS fc /b is the simplest path.

What is the minimum viable EPROM cross-validation workflow?

Two reading sources and one binary compare. Burn the chip on one programmer, read it back on a different programmer (or the same programmer at a different time), and use fc /b to binary-compare the readback against the original source file. You need two independent reading sources, not five.

How do I tell if my EPROM programmer is misreading chips?

Read the same chip three times in a row, save three separate files, and fc /b them against each other. Different scattered errors each read indicates intermittent read electronics. Identical reads that differ from the source file indicates deterministic misreading. All matching reads indicates correct reading under current conditions.

New Pickup... Atari 2600 Bundle

July 12, 2026

Picked up an Atari 2600 bundle in excellent condition! The console, 2 original CX40 Atari joysticks, 1 set of original CX-30 paddles, and 5 CIB boxed games!