No display from Power Mac G4 to 17" Apple Cinema Display using ATi Radeon 9800 PRO 256Mb, with Apple DVI to ADC adapter

3 replies [Last post]
Joined: Jan 14 2009
Posts: 2

Dear All,

In order to improve the performance of my Power Mac G4 933 MHz (Quicksilver 2002), I have recently purchased an ATI Radeon 9800 256Mb AGP graphics card from ebay. In order to use this with my 17" LCD Cinema Display, I am trying to use an Apple DVI to ADV adapter which I purchased from ebay a while ago, in anticipation of upgrading the graphics card.

The problem is then when the new graphics card is fitted, and the adapter used, I am not getting any display on the display. The monitor is receiving power, as the power light comes on, and the USB mouse and keyboard pass through works fine too, so the adapter is doing some of the things it should, but doesn't seem to be carrying the video signal properly.

In order to test things, I borrowed a PC from a friend along with the DVI monitor he uses. The DVI monitor worked fine with the new graphics card, but, as with the Mac, the adapter wouldn't display the video from the PC when I tried the adapter's DVI cable with this.

Does this mean that the adapter is broken? It seems to me the the graphics card is working fine. Does the adapter have any known faults or intermittent problems that this could be related to?

Are the any known compatibility issues with this set-up that could explain the problem? If so, is there away to get around this? I would love to be able to enjoy better graphics under OS X 10.5, and would really appreciate any advice you may be able to offer to help me with this issue.

Many thanks in anticipation,


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coius's picture
Joined: Aug 25 2004
Posts: 1975
Is this from a G5?

If this video card is from a G5, and has not had the mod, it will need to be done.

All I know is that you will have to tape certain pins on the AGP Card, and if you didn't, you *might* have already destroyed the card. It happens to be some extra power that was put into the video cards for the G5.

Second, are you sure this is a Mac Video card?

Or was the auction saying specifically it was for a mac?

If you didn't get a mac card, there might be hope yet through a Firmware flash. You would need a PC with Dos (or bootable floppy for flashing) and then again, you need a card that can be flashed.

Get back to us, preferably giving us a link the auction to let us know where you got the card, and if there's any info in it.



See my PB540c 33Mhz serve a website!

Hawaii Cruiser's picture
Joined: Jan 20 2005
Posts: 1434

I don't know if G5's came with 256mb 9800's. Some came with 128mb versions, which, for a G5, would be AGP 8x, so in order to get it to work in a G4 it would require pins 3 and 11 to be disabled, rendering it only 4x AGP. If a video card was originally an 8x AGP card and pins 3 and 11 are not disabled, a G4 tower will not even turn on.

ATI made a retail Mac Edition 256mb 9800 with DVI and VGA which only ran at AGP 4x, so it could run in both G4's and G5's.

The reason pins 3 and 11 have to be disabled is because that's where the ADC draws it power through, so in order for a DVI to ADC adapter to work, I would assume, though I've never used one, there needs to be a separate power source feeding into the adapter to power the ADC, and the ADC draws 28 volts.

Joined: Jan 14 2009
Posts: 2
Hi, Thanks for your replie


Thanks for your replies and helpful suggestions.

As far as I know, the graphics card is the Mac version. I have used it successfully in the Power Mac G4, where it booted and was recognised by the OS, and drove a DVI-monitor with not problems at all. It was sold as Mac card, and the vendor specifically stated that it was compatible with the Quicksilver G4.

The adapter I have is also a power supply for the ADC monitor, and the screen does power up, it just doesn't display anything.

As the card did work with another monitor without any problems, the issue seems to be some issue between the screen and the adapter, but I just can't see what I need to do to fix it.

Again, thanks so much for taking the time to reply; I really appreciate it.

Look forward to receiving further advice soon.

Best Wishes,