How and Why to Disable Pins 3 and 11 on AGP 8x cards in your Power Mac G4
The Short Story:
* These video cards are compatible with AGP 8x:
o GeForce 5200 or later (and some Geforce 4 MX cards with NV18 GPU, also some Geforce 4 Ti cards with NV28 GPU)
o Radeon 9200 or later
* These Power Mac G4s are compatible with ADC:
o Gigabit Ethernet
o Digital Audio
o Quicksilver 2001 & Quicksilver 2002
o Mirrored Drive Doors (MDD)
o Firewire 800
* If you have both of the above (an ADC-compatible G4 and an AGP 8x-capable video card) you MUST somehow disable pins 3 & 11, or your Mac will not boot with your new video card in it.
* There are three methods of disabling the pins:
1. Taping Over Pins
2. Desoldering Surface-Mount Resistors
3. Cutting Circuit Traces with a Sharp Blade
The Long Story:
This information is compiled largely from posts originally written at the Strangedogs forum by rubytuesday.
A few years back, Apple decided they would cut down on desk cabling (and lock in hardware sales to themselves). They did this by combining all cables for their monitors into a single one. This bizarre idea was somehow approved, because that's how Apple works sometimes. The result was that Apple's new "ADC" monitors had to be used with an Apple branded video card with an ADC output. This ADC connector had the usual DVI connections but also had connections for power to run the monitor. This power was 24-28V and came from an extra little socket added in front of the AGP connector. This socket only has 2 connections, so the other connections needed to be added into the existing AGP connector. The other connections added included USB and connections for the power switch and a button to launch "Display Preferences"
To do this little magic trick, Apple decided to use some (then) unassigned pins in the AGP connector. Two of these pins, numbers 3 & 11 on the back side of the card, later got re-assigned to be the pins that "enable" AGP 8x. What this means is that when an AGP 8x card is inserted into one of these Macs, the Mac will not even power on. Disabling pins 3 & 11 allows the Mac to run normally.
This problem only deals with the pins on the BACK side of the card. On the front (side with Fan/heatsink), if you choose to use tape, you just want it to curl around so that installing it doesn't peel it away from the connectors. And even this is optional. It is important that you disable the 3 & 11 pins on the BACK SIDE ONLY!!!! No pins on the front of the card should be modified in any way.
The second half of the story: So, Apple got caught with their pants down when the AGP 8x spec came out. Suddenley, the pins they had choosen to be the "Power On" switch (3 & 11) got assigned to AGP 8x. Suddenly, all G4's were relegated to AGP 4x cards forever since an 8x card grounded those pins. Anyhow, the net effect is that an 8x card in a pre-G5 Mac causes the Mac to seem dead. This tells you: "Time to disable your pins."
G5's brought AGP 8x compliance by redesigning the ADC plug & pins. So, again Apple thumbed their nose at everyone else, went their own way, and then quietly had to join the bandwagon later when it "didn't work out".
To clarify, the ONLY G4 which doesn't require pin disabling is the AGP 2x, pre-ADC Sawtooth (10/100, not Gigabit Ethernet). If your G4 doesn't have the ADC power tab near AGP slot, you can skip worrying about this. ALL OTHER G4s, Cube included, NEED these pins disabled.
DO NOT disable (or tape) the pins for a G5. If you buy a flashed 9800, you can REMOVE the tape if any is present. Most cards don't seem to mind, but the 6800GT will Kernel Panic at some point if the tape is left in place on a G5.
Guides for the Three Methods to Disable Pins 3 & 11:
(Photo credit to Dave Pirinelli)
This is a method specific to ATI cards. No NVIDIA cards are known to have resistors controlling pins 3 and 11. Removing these resistors will allow the card to run in ADC G4 Mac AGP slots without taping pins. As is always the case when pins 3 and 11 are disabled, the card could be problematic in an 8x slot — this is particularly an issue with NVIDIA 6800 cards. The example card shown is a Radeon 9800 Pro; identical resistors are present on the 9700 cards, and some x800s as well. Only R2 and R4 actually need to be removed. The function of R5 and R6 is unknown, but they are missing on Mac cards, so as long as you've got the soldering iron warmed up, why not?
If you have a 9600 Pro or 9600 XT card, depending on your card design, there may be some resistors for you, too. Check near the AGP connector on the back of your card, on the end nearest the video ports. If it looks like the picture below, and R60 and R15 are present, then removing those two resistors will disable pins 3 & 11 for you, no cutting or taping needed.
This is a method usable on all cards, and is the only choice other than tape on nVidia cards, as well as ATI cards not covered by the desoldering method above. The example below is a PC nVidia GeForce 5200 Ultra.
As shown below, slice the circuit trace on the card with a straight razor or other sharp blade along the green line, in the direction of the arrowhead. The green arrows indicate some good possible cutting paths:
On your card, whatever it may be, absolutely ensure that the direction that you're slicing does not leave the blade traveling in the direction of a nearby, possibly vital part of the board! It is quite possible that you will overcut, your hand will slip, and at those times, you'll wish you'd thought out your cutting path more thoroughly before going into surgery. An example of BAD choices for cutting paths is below: