HP 48 ram card from Ebay: why would self-test be required?

[mfleming]

I bought a visually similar card from a different seller a few years back and it worked fine in a 48GX. Mine is marked "Grid" as the manufacturer rather tha "VALID" but otherwise looks the same. The instructions for testing the card beats downloading a test program to do the same verification. Don't try the card in a 48SX, I locked mine up so badly I thought I had permanently damaged the processor. I don't know the provenance of these cards, but the price certainly beats that of the HP branded cards.