I was looking at the electrical pinouts and documentation of the interposer and i was wondering for the VSYS_GPU + it states that it ranges from 7-20V, does that mean that the dGPU board VRMs takes this voltage range and then steps it down to the GPU voltage or is there a convertor somewhere in the GPU module?
The VRM for the actual GPU chip itself?
If so, no, I don’t believe so. CPU & GPU VRMs purpose is to provide voltage regulation that is more stable, precise, low noise than normal regulators supply. CPU & GPU have much stricter requirements than most other components. The VRM is likely feed from another simpler regulator.
yes but the input voltage for the VRMs on a desktop GPU is regulated at 12V but for the dGPU it states that VSYS_GPU is 7-20v and I was wondering if that was fed directly to the VRMs or was there a secondary converter that step it down to 12V before it was fed to the VRMs
In laptops the vrms usually have vbus as input which is provided by the battery charge controller/power mux and is usually somwhere around the battery voltage. But in the case of the fw16 it’s probably a bit more complicated since the expansion bay is in-theory also capable of feeding power to the battery.
According to frameworks block diagram vbus is 19V on the framework 16, and both the cpu and gpu are getting 19v for their vrms. A bit weird since the charge controller responsible for that rail apparently maxes out at a bit over 18V. (Man the power system on the 16 is a mess, there are certainly hurdles when being the first to do a 48V pd setup)
On desktop the input voltage for the vrms is 12V cause that is what the atx specification provides, there is nothing magic about 12v. In the server market there are tons of things running on 24 or 48V to save copper.
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so are you saying that i should incorporate a 75w 12v converter for the pcie x16 slot that gets power from the VSYS_GPU (7-20v)
Depends on what you want to do
I want to create an expansion bay that will have a pcie x16 slot on the back so i can connect an External GPU to it. I am aware that only 8 of the lanes will be used. I need to get 12V for the slot and i am planning to put a converter from the VSYS_GPU to 12V on my board
If you don’t want to use external power for your egpu then yes it looks like you are going to need a buck converter. What card do you want to put in there though, I don’t know of a lot of worthwhile gpus that don’t need additional power? The 6400, gtx 1650 and arc a310 are in the same ballpark as the igpu so imo not really worth the effort and if you already have an external power supply just get the slot power from there.
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this is what i have so far GitHub - Ether-Nova/FW16-pcie-expansion-bay
I agree that most GPU’s will draw more than the 75W allotted from the slot but i plan to make this slot more than just for GPU’s which have external power connectors
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