This should all be clear from the scheme:
So, it’s easy to find the total power consumption of a graphics card from the additional power connector.
Well, this is only a portion of all the consumed power. Besides the 5v and 12v circuits that go through the additional power connector(s), there are also 3.3v, 5v and 12v power circuits going through the AGP slot. It’s more difficult to measure the current flowing in these circuits – you can’t plug an adapter with the shunts into the AGP slot!
What to do? I took it easy and just insulated the appropriate pins of the AGP connector on the graphics card with stripes of adhesive tape (pin A1 – 12v; pins B2, B3 – 5v; pins A9, B9, A16, B16, A25, B25, A28, B28 – 3.3v) and applied those voltages directly to the graphics card, through the prepared shunt, taking the voltages from the PSU.
This gave me more trouble with each of the cards – I had to mess around with scissors and tape searching for any points to attach 3.3v, 5v and 12v lines to and soldering wires to them – but this allowed calculating the total power consumption of the card with more precision. Moreover, some of the graphics cards don’t have an additional power connector, so the powering through the shunt, bypassing the AGP slot, was the only way of measuring their power consumption.
Testbed and Methods
I tested the graphics cards on the following testbed:
- AMD Athlon 64 3400+ CPU;
- ASUS K8V-SE mainboard;
- 2x512MB TwinMOS PC3200 DDR SDRAM, CL2.5.
- Windows XP Pro SP1;
- DirectX 9.0b;
- Catalyst driver version 4.7.
I measured the power consumption in two modes: “Idle” and “Burn”. There were no running applications in the Idle mode; the screen was displaying the Windows Desktop with a scattering of standard icons in the 1280x1024x32@75Hz display mode. The Burn mode used one of the scenes from Far Cry in the 1600x1200 resolution with forced 4x full-screen antialiasing and 16x anisotropic filtering. On the Training level, near the hut with the binoculars, I saved the game and used this save with all the graphics cards to create the identical test conditions.
I also ruminated on the idea of using 3DMark 2001, 3DMark03, Unreal Tournament 2004 or “IL-2: Sturmovik” for the tests in the Burn mode, but the scene from Far Cry proved to be the heaviest of all for the graphics cards.