Mechanical changes to the header (socket)
The biggest change is to the so-called header, i.e. the socket that is also soldered to the expansion cards such as graphics cards. The 12V-2×6 connector is conditionally compatible to older graphics cards with 12VHPWR header and the current 12VHPWR connector cables of the power supplies as well as the adapters will again be more or less compatible to the 12V-2×6 header. Twelve large contacts carry the power rail, as before, and four smaller contacts below that carry sideband signals. That’s where the biggest changes are.
By the way, the 12VHPWR coding update is also done to accurately reflect the published CEM 5.0 (because the base specification and CEM 5.0 were even inconsistent). For expansion cards with 150 watts or 300 watts, new rules apply and the detection of the 150 watt cards even still requires external circuitry (see at the end of page). It is also logical that the 12V-2×6 is of course still not compatible with the PCI Express 2×3 and 2×4 PCIe connectors (Aux). The power pins of the 12V-2×6 connector have a pitch of 3.0 mm, while the contacts in a 2×3 and 2×4 connector are on a larger pitch of 4.2 mm.
I already wrote more than half a year ago that the PCI SIG will mechanically reset the four lower, so-called sense pins of the sideband signals, i.e. shorten them. As long as the connector is then not far enough in the header (until it snaps in), the sideband signal of the two pins for the detection is missing. Thus the card is not switched on at all or is switched off immediately if the connector slips out unintentionally. We can see on the first picture that the sense pins of the 12VHPWR are 4 mm long and sit 0.45 mm behind the outer edge of the header. The final contact point sits at 3 mm behind the edge of the opening.
The 12V-2×6 header has the same outer dimensions, also the final pressure point of the sense pins is again 3 mm to ensure compatibility. But now it gets interesting. The tips of the sense pins are now offset 1.7 mm inward, a change of 1.25 mm. The actual pin behind the tip, where there is first contact, is now even 2 mm behind the outer edge. This creates significantly more safety.
New power classes with 150 and 300 watts
By connecting pin 0 to ground and leaving pin 1 open, you can achieve 300 watts. The 150 Watt circuit is tricky and new: Pin 0 and pin 1 are simply connected directly and without ground. This in turn requires new cables or a special power supply:
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