I know for sure Intel server CPUs (for example, Xeons) don’t have integrated graphics and somebody else mentioned that many Ryzen CPUs don’t either.

That said, I’m not sure if they need integrated graphics to have hardware decoding for certain video codecs (though it makes sense that those things come together). Personally when I was looking into buying a mini-PC to transform into a media server for my living room, I made sure to check in the CPU specs if it had both integrated graphics (as it’s connected to my TV) and hardware decoding for the most recent codecs (I ended up going for a mini-PC with an N100 processor, since it has all that plus its power consumption is pretty low with a TDP of 6W so I can leave it always on as it also doubles as homeserver).

I actually have a Mini-PC with an N100 CPU and no dedicated GPU as media server and it uses very little CPU (less than 20%) whilst playing 1080p video even with a torrent server over a wireguard VPN running on the background.

You don’t really need much CPU or GPU for playing or streaming videos from compress video files as long as you have hardware decoding on either processing unit (just make sure it implements all the way up to the AV1 coded).

You only need lots of CPU or GPU power if the codec you’re decoding from or encoding to is not implemented in hardware since in that case it will use software decoding or encoding so it’s down to raw CPU or GPU power.

In fact if all you want is a media server that solution I have is probably one of the best ones, mainly because it uses very little power (tops at 25W, usually much less) and runs silent, which is why I can have it in my living room using it as a media player connected to my TV, and with a wireless remote people can’t really tell it’s a PC since it just looks and works like a store bought media player rather than one I put together myself.

However that option means buying new stuff, and I can see the value in using old hardware if you have it around, plus the old hardware will still likely be more powerful so you can also use it for more demanding stuff or just more stuff at the same time, which is why I didn’t suggest it and instead just suggested some tweaks to make that old hardware consume less and make less noise.

underclock and undervolt

If I’m not mistake only hobbyist level motherboards let you control the voltages and if one knows enough to get one of those they probably don’t need the advice I gave.

Also it’s hard to end up with a non-working or unstable configuration with underclocking, whilst it’s pretty easy to do so with undervoltage.

That said, for those who know what they’re doing, your suggestion definitely delivers lowers temperatures than underclocking alone though at the risk of a less stable system (which can be ameliorated with proper stress testing).

For anybody not doing generative AI with it and not running massive loads on it, if you’re going to use an old gaming PC as a home server, at least replace the graphics card with a cheap one with no fans or use the integrated graphics on your CPU (something I believe pretty much all consumer CPUs of the last two decades have) and underclock the CPU if you don’t need full processing power since even small reductions in clock speed can significantly reduce the maximum temperature.

Provide a means for people to charge their phones = Instant Hero.