The C64 Dead Test Font

The C64 Dead Test Font

May 24, 2026

A deep dive into the font of the “Dead Test” diagnostic cartridge of the C64, including an Easter egg, a look into the implementation, and, finally, some Commodore 8-bit character ROMs for download.

Recently, having a cursory look around at the Web, this yielded an alarming result: there’s apparently no documentation of the iconic font of the C64 Dead Test cartridge, no character chart, no read-out, nothing of note. A scandalous omission, we’re attempting to remedy here, for once.

(The same font, BTW, is also implemented in the more advanced Rev. 586200 diagnostic cartridge, Commodore part № 326070-01, the one using a test harness, and the similar Rev. 588220 for the SX64.)

The Cartridge Font

The C64 “Dead Test” diagnostic cartridge Rev. 718220 (Commodore part № 314139-03) famously comes with a special font, embedded in its ROM, thus not using the built-in Character ROM of the C64, in fact requiring none of the built-in ROMs to be working (hence the name), as it comes all in stand-alone package. (We’ll see later how it does this.) Its display font is somewhat special and is, to my knowledge, not used anywhere else and, maybe for this very fact, instantly recognizable to anyone who has ever seen it.

And this is what the display of the “Dead Test” cartridge looks like:

Screenshot of the C64 Dead Test diagnostic cartridge in action.

Source: zimmers.net (processed for CRT-like appearance; N.L.)

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