I have an older power supply rated for 650 Watts that doesn't have the extra four-pin CPU power connector that many of the newer power supplies have, mine only has a single eight-pin CPU power connector.
How important is that extra four-pin connector? Do I absolutely need it? Or can I get away with running a Z690 board and a 13th gen Intel chip without it?
In theory a single 8 pin CPU power connector can provide 28A/336W, while it is safer to predict on its ~80% efficiency due to circuit loss but you are still good for basically anything unless doing some really heavy overclocked and heavy full thread loads. If you are going to overclock and hit it hard on cinebench I would definitely find the 4pin and connect it, but if you are just gaming and doing some daily tasks I wouldn't worry too much about it.
@trparky
Single 8 pin is fine. Numbers for the 8 Pin ATX12V provided by @Yingdong are correct. To get that number the connector has 4x12V and 4xGround. 12V*4(Wires)*7A(Safe amperage on an 18 gauge cable)=336(Watts). The only Intel 13th Gen CPU that would exceed that would be the 13900K on a Multi-Core stress test intended to push the CPU to maximum power draw. And in that situation, thermals are going to be a limitation on the power draw. I would say even with a 13900K, this would only be a concern under an a heavy OC with a high end cooling solution that is going to be able to dissipate a 350W+ draw for any amount of time.
For 80+ efficiency ratings, you should expect the PSU to deliver 100% of the 336W to your board via DC. The efficiency loss is from the wall to the PC in the AC to DC conversion loss. If your PC draws 750W at the wall on a 60-70% load, expect the PC is probably actually using about 675W on an 80+ Gold PSU.
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