Update
Thought I'd post an update. As it is everything suddenly appears to be working perfectly. To be honest I'm not entirely sure what happened.
I reverted from the new sapphire bios to the stock bios with the intention of making sure I could get the card working in Windows. Initially I couldn't, I'm not sure whether it was possibly user error, a bad connection or bad setup, the Windows BIOS tool wasn't recognising the bios or letting me copy it off the card. Eventually I got an output (small square of extended desktop) after playing around, rebooted and got full screen but it was still extended desktop, bit more playing and I got the primary screen via the 4890.
I now suspected that trying the flash again might get me somewhere. So I did it, rebooted SL, and it got past the grey screen with the apple logo but then hung. Rebooted back in to Windows to check the new bios and it worked in Windows and was reporting correctly. I then rebooted back in to OS X but accidentally into Leopard, but it worked. Then booted in to SL and went through fine, installed the QE_CI update and low and behold it's swimmingly good.
And, I realise I may get scorned for this but I am running a MacPro 1,1 with a 7300, my primary reason for going through this process was to speed up Aperture 3 when processing 21mp pix without gifting Apple unwarranted cash, either through an unsupported, over priced 4870 upgrade or via a full hardware refresh. So far I'd say it's a success, Aperture 3 flies, bit more memory and I'd say I'm set fair for a few years with this beast yet. I do get the power warning but it's not a worry to be honest.
Cindori and the rest I salute you, I will be contributing some of my savings to your account, I won't tell you what to spend it on but spend some of it on a beer and I'll be very happy
![Big Grin :D :D](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
--- actually Cindori the donate link at the top of thread doesn't work, perhaps you could update or PM me, thanks mate.
Confirmation of specs: Mac Pro 1,1, Sapphire 4890 New Edition w/Hynix (11150-11-20R), flashed with bios from ROMs folder, 4890 in slot 1, 7300 in slot 4