Advanced Micro Devices Inc (AMD)

[CombJelly]

"Could it be there's more to SOI than the additional costs of the discs alone?"

The cost of the wafers are a bit of a red herring. Sure, they are, or at least used to be, 10x the price of bulk. At 200mm, that meant $500 vs. $50. I think currently they are closer to $200, but let us tick with $500. That is a lot, but a fully processed bulk wafer means an investment of $2.5k to $3k. So an SOI wafer becomes an investment of $3k to $3.5k. Even factoring in lower yields due to higher defects on SOI, that still means on a large chip with a selling price of >$100, it costs an additional $10 or so, probably less. Now that is real money, but if it results in a more desireable chip, so be it. For those that sell under $100, those are smaller chips with more chips per wafer and less overhead per chip. So it can still work out as long as you stay out of the under $30 market...