Unfortunately counterfeit Motorola 68k processors are common these days as supply on the second-hand market dwindles. Very often these chips are functional and are of the correct model, but may be missing features, require additional cooling due to older production processes, or contain significant errata. When FPU functionality is critical, you’re looking to overclock, or you can’t afford a bug, this leads to wasted time and money.

Typically, these chips are counterfeit through relabelling; the original markings are ground off and new ones painted on. Without the chip physically in hand, however, this can be difficult to identify.

This guide discusses key chip markings which can indicate tampering from images. It’s built as a summary of how to use my extended index of 68k chip data. You’ll need a clear, readable picture of the top of the chip, at minimum.

Reading Chip Markings

Before we begin, you need to understand how to read chip markings, including the product number, mask, test traceability code, location, and the package-related identifier.

You can read how to do this with my guide to reading chip markings.

Bad Signs

If your chip has any of these bad signs, it may be counterfeit. If it has multiple signs, it almost certainly counterfeit.

Missing or Incorrect Markings

Consult the chip marking guide. Most of the standard markings should be present on all legitimate chips. For instance, an MC68040 should have at least 6 separate markings present. If they are missing your chip may be counterfeit.

If the markings are present but don’t follow the correct format (for instance, the test traceability code does not contain 4 digits for the date), your chip may be counterfeit.

Incorrect Die Size

For PGA chips, the size of the gold cover plate on the bottom of chips can vary according to manufacturing process. My index does not cover this data currently, but a general rule of thumb is that a revision with a smaller process can have a smaller plate. It should correspond to the mask for the chip. If you compare the chip with another of the same mask and the cover plate is larger, it may be counterfeit.

Mask

Fake Mask

Consult the 68020, 68030, 68040, or 68LC040 table. The mask specified on the chip must be real, meaning it corresponds to the correct type of chip. Masks are (almost) never used for multiple different chips. If the mask listed is not a known version for this chip, it may be counterfeit.

Test Traceability Code

Implausible Type

Manufacturers often used XC-type parts, which are not fully qualified, as opposed to MC parts which are. This is fine for many applications, and isn’t a sign of an issue.

However, only certain masks were MC qualified, and only after a certain date. Consult the 68020, 68030, 68040, or 68LC040 table. If your chip is marked with type MC but doesn’t correspond to an MC qualified mask, it may be counterfeit.

It is okay for a normally MC mask to be marked XC (it may have been delivered during verification of the mask).

Fake Year

Consult the 68020, 68030, 68040, or 68LC040 table. The year must be plausible for the period the chip was released, the introduction and cancellation dates for the mask, and the qualification status. If your chip has a mismatched year, or even impossible numbers (like 33 for 1933 or 2033), it may be counterfeit.

Additionally, if your chip is marked Freescale but was made before 2004 (when Freescale was founded), it may be counterfeit.

Fake Week

There are only 52 (or 53 depending on how you count) weeks in the year. If the week is larger than 53, your chip may be counterfeit.

Assembly Location

If a location is printed on your chip (like MALAYSIA), the assembly location code must match. These markings serve two different purposes, with test traceability for Motorola, and location for legal reasons around global trade. As a result, they contain the same data in a different format. For example, the letter Q is used for Malaysia. If they do not match, your chip may be counterfeit.

Package-Related Identifier

Mismatched Identifier

Consult the 68020, 68030, 68040, or 68LC040 table. The purpose of this identifier is unknown, but it does correspond to the mask. Verify that this identifier corresponds to the correct mask if this data is known. If it does not, your chip may be counterfeit.