Because as stated previously the ROM of the Sonnet card has been flashed with R1, and R1 won't recognize the video chip in R2 Wallstreets.

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How do you know it is flashed with a R1 ROM? A R2 (to the best of my knowledge) will work fine in a R1. This is why you can use R2 cpu boards in a R1 mb, but not vice versa.

Thus, the fact that it works in a R1 PB does not explicitly imply that it is a R1 ROM. It could be either R1 or R2.