I believe it's a 40nm card because if it is a 55nm i don't see the reason for the delay. At 55nm they should be able to foresee what they could and not do due to power limitations several months ago. So they could have launched the 55nm r790 at january as a response to the 285 which first benchmarks was available since the mid december, and ati already knew what would be 285 perfomance more or less and i don't believe they started r790 design after 285 was released. All that of course based on the fact that r790 is not a complete redesign on 55nm because it doesn't make much sense and either way even that wouldn't delay so much as april, since 55nm is a known process.