No. It will put Apple EFI firmware which is 32/64-agnostic.
Strictly speaking EBC (EFI byte code) is an EFI standard. It abstracts the function calls to make them compatible with either 32bit or 64bit EFI platforms. When I read some of the documents, it implies a few coding considerations, which happily the Apple engineers took the care and time to do. That's why the ATI family of cards have been easier to make backwardly compatible with 1,1 and 2,1 MacPros.
EBC is analogous to Java code, it is portable. Byte code is an intermediate format.
Netkas and the guys over at his forum were able to extract the EBC section of Apple supplied AMD/ATI cards, figure out how to remove some restrictions/protections, such that the EBC could be appended to a stock BIOS ROM. The typical approach is to dump a copy of your card's ROM, then use an editor to append the EBC to the end, and then fix up a couple of locations so that the Hybrid ROM advertises the fact that there are now two ROM sections available in the firmware. Everyone is encouraged to use their own card's ROM as the donor since it means the card manufacturer and model IDs don't get mixed up, which can cause some issues.
The Apple EFI environment will find the EBC section, and use that to initialise the EFI display environment. There's still a lot of issues with card physical and logical data paths, but most cards match closely enough that Apple's EFI environment can then push the video signal out via the digital connectors, hence we get to see the boot screens. The EBC doesn't need to be that complex because the EFI environment doesn't need high performance.
Once The EFI hands control over to the MacOSX kernel, its job is done. The OS then uses the full feature set from the original BIOS section, matching the (driver) kernel extention (kext). That's why most BIOS-only cards begin working once Mac OS X is booted.
Unfortunately for MacPro owners, almost all Apple-compatible Nvidia cards have full-blown 64-bit EFI sections (not EBC), which is why most Nvidia cards are not compatible with our old Macs
for boot screens, (they still work great once the OS is loaded). The EFI sections would need to be re-written to be compatible with 32-bit EFI hosts, or re-written to compile into EBC.
