Test results for 5-series board P55-UD6 running W7 x64.
First of all with the standard 11.6 OROM and 11.2 driver.
As expected, trim gets rejected by the driver.
Changing 2 bytes then using the same customized trim command to trim sectors 16 thru 31 the 11.2 driver reports success and the results verify that trim has indeed been performed.
Before trim command
After trim command
Another test by deleting the file cpu.txt.txt (yes, normally it should only be one ".txt" but unfortunately that's how it was saved :p).
So it would seem likely that all boards with a PCH controller that support RAID0 can support trim with a trivial change to the OROM, that is except the X79. Unless the X79 supports changing the SATA controller ID from 2826 to 2822 similar in the way the P67 controller can change from 2822 to 2826 then I think a bigger change would be necessary. In the case the X79 was able to use ID 2822 then I think possibly no changes would need to be made to the OROM at all, only that the BIOS support the changing of ID of the SATA controller.
From these findings I feel very optimistic that Intel would include the other PCH series in a future OROM release otherwise why have they made it so simple to add the other 5 and 6 series boards. I would like to explain this better by posting a small hex output of a few bytes of the OROM but do not know if doing so will have ermm "repercussions". I would be grateful if Anand or a mod would be kind enough to comment on this dilemma, comments from Intel employees who frequent this board would be welcomed too.
BonzaiDuck, thanks for mentioning the torqx 2 utility, I have not come across that one so have downloaded it and will give it a try sometime. Intel seem to like to hold their cards very close while often it seems remaining in silence. With the currently available OROM's as is, trim is only available on 7 series, excluding X79, so their position IMO would likely to be to say only that 7-series is "supported" without any further information such as "we plan to add support for earlier chipsets" or "we are not going to support any earlier chipsets. IMHO this leaves people not knowing what is really going on and resulting in speculation and for me, why I felt it necessary to see if trim was even possible on the earlier chipsets.