G92 EFI 32 / 64 Discovery via the 8800GT

Discussion in 'Mac Pro' started by MacVidCards, Sep 13, 2009.

  1. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    I always thought it was odd that the EFI32 Apple Rom for 8800GT used an oddball device id of "602" while the EFI64 one used the more common device id of "611".

    The PC BIOS that actually runs the card is different on the different Apple ROMs. I couldn't imagine why Apple wouldn't have used the same PC BIOS, it would seem much easier to interface with if you had already written with it.

    Today I was doing some more G92 fiddling and I flashed a 8800GT with the EFI64 ROM. As expected it doesn't boot as a Mac card in my EFI32 Pro.

    However, when I went into Windows, I discovered something. The EFI64 version was throttling, just like the new GTX285. This is now standard procedure for Nvidia PC cards, I think all 9800 series and probably all of the G200 cards do it to reduce power and heat.

    So...the EFI64 card is designed to throttle clocks speeds to respond to load but nobody has noticed this and complained the way they did for GTX285. Perhaps the EI64 machines have added part of EFI that defines how Pro interacts with GPU speed, hence it not being present in EFI32 ROM.

    Oddly, the EFI32 card came out AFTER the EFI64 card. Perhaps they were rushed to market and didn't want to bother with the throttling triggers.

    Or maybe...they just wanted the EFI32 card to die an early death from running at wide open clock speeds all the time.

    As I recall, there was some OSX update or another that resulted in much screaming involving the sudden deaths of 8800GT cards...I wonder if they were mostly on 1st Gen / EFI32 machines.

    It just occurred to me that I may be able to get the EFI64 8800GT to run in OSX on my EFI32 Mac using Netkas little bag'o'tricks. Think I'll give that a go and see if it is throttling there.

    And if anyone has an OEM 8800GT EFI32 with a device id of 611 or an EFI64 8800GT with a device id of 602, I would like to get a look at the ROMs.

    The attached pix are from running Rivatuner Hardware Monitor whilst launching and playing some Halo2 in Vista 64. You can clearly see the EFI64 card raising and lowering clock speeds in concert with demand, temps rising and fan speeding up to match.

    The EFI32 pic shows flatline clocks on all three measured levels. This is the equivalent of driving your car everywhere in second gear all the time with engine racing. You wouldn't expect the car to last long.

    Attached Files:

  2. haveagoal macrumors newbie

    Feb 3, 2010
    I think it might be nice to post a list of all G92 based cards that have 128k roms, cards that can be flashed as is that just work and cards that require modifications (hardware/software) with some kind of rating system for functionality/success.

    Another one for the books, an associate had a china brand (Sparkle we think) Dual-DVI 9500 GT 512MB with 128k rom which he flashed apple's GT120 firmware and the card works properly, actually maybe it's better cause he now has Dual-DVI.

    The upper port is the primary port (this is normally the secondary port) and the S-Video is non-functional cause the apple firmware reroutes this to the secondary port but both DVI's seem fully functional.

    At this time we do not know the exact manufacturer or model but he is trying to track down a receipt so we can find out exactly what card it is and check on pricing and availability but it is looks like an alternative to the 8800 GT that might prove to be inexpensive.

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