Do I need 4 x 8pin to enable 12VHPWR 600w mode?
NO, you do NOT need 4 x 8pin to enable 600w mode in 12VHPWR.
This is a common misunderstanding and misinformation on the Internet about this.
This misunderstanding is due to the original Nvidia adapter added a limiter IC which it will downgrade to 450w from 600w when only 3 x 8pin is connected. This limiter happens and applies to the original Nvidia adapter only, and this causes all the confusion and misunderstanding on the Internet.
The GPU does not know and do not care how many 8pin you have connected. You can use and enable 600w mode with 2 x 8pin, 3 x 8pin, or 4 x 8pin cables.
You may have also seen PSU vendors offering 2 x 8pin cables which support full 600w mode, and this can help to prove the point.
For modern and good quality PSUs (e.g. Corsair, EVGA, Seasonic, Lian Li), each 8pin modular port can support 300w. So 2 x 8pin means 300w + 300w = 600w, while 4090 is a 450w card only.
By using 2x8pin, you can already enable 600w mode which many people refer it as 133% (the extra 33% means 33% on top of a 450w GPU, 450w + 150w= 600w)
By using 3 x 8pin port, the PSU can support 300w + 300w + 300w = 900w which is way more than enough already.
4 x 8pin is not necessary at all if you are using a modern PSU from a reputable brand.
This is a common misunderstanding and misinformation on the Internet about this.
This misunderstanding is due to the original Nvidia adapter added a limiter IC which it will downgrade to 450w from 600w when only 3 x 8pin is connected. This limiter happens and applies to the original Nvidia adapter only, and this causes all the confusion and misunderstanding on the Internet.
The GPU does not know and do not care how many 8pin you have connected. You can use and enable 600w mode with 2 x 8pin, 3 x 8pin, or 4 x 8pin cables.
You may have also seen PSU vendors offering 2 x 8pin cables which support full 600w mode, and this can help to prove the point.
For modern and good quality PSUs (e.g. Corsair, EVGA, Seasonic, Lian Li), each 8pin modular port can support 300w. So 2 x 8pin means 300w + 300w = 600w, while 4090 is a 450w card only.
By using 2x8pin, you can already enable 600w mode which many people refer it as 133% (the extra 33% means 33% on top of a 450w GPU, 450w + 150w= 600w)
By using 3 x 8pin port, the PSU can support 300w + 300w + 300w = 900w which is way more than enough already.
4 x 8pin is not necessary at all if you are using a modern PSU from a reputable brand.
Updated on: 26/10/2022
Thank you!