Thanks for starting this thread, quick background, I had been running a 2006 with mavericks but it was taking 20mins to boot as it looked for the boot disk not a problem in daily use as it rarely needed rebooting so I never bothered to fix it properly but with my laptop and work mini running yosemite I dreaded the hassle of upgrading it and one thing led to another.
I bought a dual 5,1 mac pro with the quad 2.4Ghz cpus. First step was a ram upgrade - if you want ultimate speed I was able to borrow lots of ram to test and for maximum speed (the hit isn't too much using all 8 slots but it shows on geekbench) don't use slots 4 and 8 just 1-3 and 5-7, I currently have 6 x 16Gb installed.
Next was upgrade to ssd using sonnet tempro ssd pcie pro card - still work in progress as I need to boot into bootcamp for the card flashing and it kept getting confiused and crashing - as I had made a few changes in quite a short Time I wasn't sure what was causing it to crash when waking from sleep so I removed teh temp as a first step.
Ordered a pair of 3.06 Hexa x5675 CPUs from UK as I didn't want to mess with an external power supply and these are the fastest low power CPUs - installed these and now geekbenching happily around or over 28500.
I would like a 4K monitor so next step was to replace the HD5770 card with a new one, I found this thread saw the bios there ready and waiting so I ordered the exact same MSI card.
Trying to avoid too much work I threw caution to the wind and flashed it with mr Zarniwoops bios, looked great and appeared to work fine except that the RAM on the card was showing wrongly a huge amount, I was not sure if this is just cosmetic or affects performance. Then I see mamfo had the exact same problem, great I think I will just use the rom posted for hi,e unfortunately I get VBIOS not found error when trying to flash with his rom but the original Zarniwoops bios flashes fine. I opened both up in a hex editor and can only see the bios string as being different, I double checked using cpuz that mamfo bios is the same as mine which it is. (however both have x77 at the end and its written as 077 in the bios - does that matter?)
Is there any actual difference in the legacy and uefi bios switchable rom areas?
Next step is to try a hex edit of mr zarniwoops rom to add my bios (legacy) but I don't understand why mamfo's bios does not work when its only the bios string itself thats different.
I could live with mr Zarniwoops bios as long as I know that the incorrect RAM amount is just a comment (shows up in windows gpuz incorrect as well) and doesn't affect speed
Lastly it came with the switch set to uefi boot not legacy which I where I flashed it to originally - yes without backup but I was expecting it to work and I am not worried about installing the card in windows 8 at any time, I did backup the legacy rom though
Bios Version Graphic Card:
015.044.000.007.000000.(113-C3865000-X77)