Flashed 4870s offer DVI boot screen.
Flashed 5870s only have boot screen via a DVI to VGA converter on lower DVI port. When Netkas modded the EFI to work he didn't have a Mac Pro to test on, so amazing that it works as well as it does. In some OS versions the DP will work, in others, no.
Used in a 4,1 flashed to 5,1 you can actually send Audio via HDMI or DP.
REFERENCE BOARD EXPLANATION:
When a GPU manufacturer (NVIDIA OR AMD/ATI) first creates a new GPU, they send out a completed design for the board and cooler. This is the "reference" design. All the "board partners" (EVGA, XFX, HIS, etc) buy the GPU chips and use the original design to start production.
Since all electronics (except Apple) go down in price as they age, the board partners start looking for ways to cut manufacturing costs. They figure out that removing a power stage only adds 10% instability so they do it. Removing a bunch of capacitors means lower clocks but 5% cheaper, so they do it. They also frequently remove the pricey rear exit 4 wire fan designed into the reference board. They replace it with a 2 wire center mounted cheapey blasting air all over the inside of your machine. With no speed controller the 2 wire fan will fry it's little self right around the time the warranty runs out. Perfect for them.
Apple gets cards from GPU companies when they are first released and starts working on their version. SO they get a "reference" version and make their changes. Hence the reason that reference PC boards make best candidates for flashing as they have the most in common with the board Apple started with.
This became painfully obvious for people who bought later 4870s. While the early XFX ZDFC ZHFC 4870S with reference cooler were the BEST to flash. (only 1GB model to have Dual Display in 10.5.8) the later XFX models are literally the WORST models to flash (The ZWFC is basically unusable )
So there is the story behind "reference" board for Mac GPU flashing. Someone sticky that or something.
