I’m trying to understand what is driving Framework’s recommendations around PSU sizing for builds with the FWDesktop mainboard.
Framwork recommends 300W for a base setup including motherboard, 128GB RAM, cooling fan, 2xSSD, ethernet, keyboard/mouse. They up that to 400W if you use the PCIe slot, add more fans, or do something more on USB. (source)
But trying to understand where those 300W/400W numbers come from, I can’t get anywhere near it with the component power draws:
AMD spec sheet show the base TBD of the Ryzen 9 AI Max+ 395+ as 55W, configurable from 45-120W. (source)
LPDDR5X apparently tops out at around ~20W
For SSDs, 4TB NVMe use up to ~10W max, so ~20W for two
5Gbps Ethernet RJ45 supposedly <5W at max speed
Wi-Fi 7 M.2 A+E key supposedly <4W at max speed AND doing BT as well
Keyboard & mouse together is <5W
So even if the FWD is boosting up to the 120W max, and factoring in RAM (20W), 2xSSD (20W) and keyboard/mouse/ethernet/wifi/BT (14W), it still seems the total is under 175W.
Given this, why would the PSU recommendation be nearly 75% higher than the combined numbers under full load?
I’m asking since there are a wide variety of 200W and 250W DC-ATX power solutions that fit inside very compact cases. By simple math, the 250W products seem like they would have plenty of headroom despite being 50W under the Framework recommendation. Thoughts?
I acknowledge that the 200W DC-ATX options does sound too low, but if one ditched WiFi/BT/Keyboard/mouse (headless server case with good cooling) and only ran 1xSSD then the power draw maxes out at under 150W and then even the 200W DC-ATX seems like it might be viable. Am I calculating things correctly here / does this make sense?
edit: checked the BIOS, no options to limit boosting, no control of boosting at all. Updated the#sto match. Also, big sad that Framework’s BIOS is so limited compared to other manufacturers e.g. Minisforum.
I don’t own a FW Desktop yet, so i might be wrong. I do own another AI Max 395 though.
The APU may be spec’d by AMD for a max of 120W, but it can very well pull a peak of 140W if you give it enough cooling. I have no idea why that isn’t in the spec sheet, but that can even happen when you have a bios that lets you set the tdp at 120W. Given that you can still get about 80 to 90% of the performance at 80W tdp (and that the power spikes will be much less problematic there) i don’t think a bios setting is too much to ask for though.
Next, my 4tb crucial PCIe5 SSDs can pull up to 11.7W even when in a PCIe4 slot, so my guess would be that they also considered some headroom and estimated 15W peak each.
Additionally you may only use a usb keyboard and mouse, but the Desktop has six USB ports (2x USB3, 2x USB4, 2x front panel modules) which can theoretically pull 15W each (i know there is a bios issue where the USB4s can currently not supply full power in some cases, but it is intended for it). That pushes the maximum power use without the PCIe slot to around 290W and is likely where they got their 300W recommendation from.
PCIe spec says the slot has to provide at least 75W, and given recent GPUs lighting PCs on fire i don’t think adding 100W to be safe if you want to use it is too much to ask.
In my opinion you could still go with a 200W PSU if you know you’ll only use one SSD and make sure to never use any power hungry USB devices (or run them through a powered hub), but at least make sure that PSU has some form of overload protection so your worst case is limited to the machine crashing instead of catching your PSU on fire.
For the APU it is even more, in perfo mode, framework config it with a 160W for a few seconde (30/60? can’t remember)
Then you also have to add the losses on the voltage converters…
Cooling fan
with 1 SSD, no wifi card, no screen, full bf16 AVX512 load I already measured it at the outlet ~250W with a GOLD 850W PSU…
To change power limit no need for BIOS config it is OS config.
Look some use the 250W power but limit to balanced mode. (ie 120W boost with 100W continue)
After a power supply is not at its best (aging efficiency) at its maximum, but rather at half. So if you think to use for long hight power (gaming, or compute… for me it is a full GPU compute for 7 days now )
So a good 250W look is possible, but I don’t think a 200W will be good…
A BIOS tdp setting would be more reliable. You don’t want your machine to draw the higher Power levels until your OS is loaded after you put in a lower spec psu. Or when you boot some tool directly from usb (Clonezilla or some live OS USB for example).
Your Measurement with the 850W PSU might be off, but i don’t know relevant that is. The Gold certification is given for the efficiency at a specific load and below 1/3 its max load even a gold PSU can be very inefficient. Direct DC to DC PSUs are also a lot more efficient than any standard AC PSU.
that Framework’s BIOS is so limited compared to other manufacturers e.g. Minisforum.
)