I thought I'd share my experiences building a semi-passive APU (4650G) HTPC this past November. In short: these APUs are
ridiculously easy to cool. Sadly I haven't had the time/energy/whatever to finish my build log (I've also yet to install the last custom top panel for my case, which is at least part of my excuse!). But I can share some experiences still.
My build: ASRock B550m ITX/ac, Ryzen 5 Pro 4650G (Ebay purchase), 16GB of DDR4-3200 (Micron rev.E), a single cheap 512GB NVMe SSD, Lazer3D HT5 case, MeanWell RPS-200-12C PSU + a G.Unique Archdaemon PicoPSU. This was a kind-of cost-down bulild focusing on finding the ideal balance of price, size, silence and performance. Overall, I think I nailed it. Yes, I am very humble
The case might be too big for you, but IMO it's amazing due to its flexibility (can fit an LP GPU if you want, can easily fit an integrated PSU, has support for sufficiently tall coolers for semi-passive cooling, and Kevin at Lazer3D is incredibly flexible in whipping up custom ventilation patterns and the like if you want (or at least he was for me!)). This is the best-looking pic I have of the system mostly assembled, though this is non-final, and I use the PC mounted horizontally and not vertically like shown.
That thick fan takes up a lot of space:
The janky part of my build: I'm using a modified (read: rather mangled) Arctic Accelero S1 passive GPU cooler as a CPU cooler, with custom laser cut aluminium mounting hardware. It has a 140mm Noctua fan sitting on top of it (exhausting out the top panel), which turns off when the CPU is below 65°C. That's easily >90% of the time, and it even shuts off periodically while gaming! As I said, this APU is ridiculously easy to cool. This PC never really sees sustained CPU loads, but it handles them excellently from when I've stressed it. I would imagine a Noctua L12S would be able to keep it very cool, though its passive performance might not be as good due to its denser fin array. Still, I would be shocked if a setup like that wasn't
very quiet.
As for that mangled heatsink: this is what I had to do to fit the 140x25mm fan and the ArchDaemon:
Yeah, that part isn't pretty. Though it does say something about how durable heatpipes are
The RAM is also squeezed in between the fins. So, going for an off-the-shelf cooler like the L12S is probably a better bet!
I run my CPU at stock, with the RAM OC'd to 3800MT/s and IF at 1:1/1900MHz. As mentioned above, the fan only kicks in if the CPU exceeds 65°C, which doesn't really happen at all in regular HTPC use, and when I play some Rocket League (runs great at 1600x900 medium or 1080p low-ish with FreeSync delivering a smooth ~90fps) the fan goes between off and on every minute or so. It runs
ridiculously cool for what it is.
The 200W RPS-200-12C is more than sufficient for powering this build - the highest power draw I've measured at the wall (with a +/- 5W margin of error according to my cheap meter) is ~110W when stressing both the CPU and GPU, with the memory and IF clocked high. The PSU is rated for more than that entirely passively, so the single fan in the system only kicking in under load should work excellently.
So, my recommendation would definitely to go for a 5600G when it arrives, as keeping it cool silently should be relatively simple. You can always get a smaller build than mine, but it won't be silent - a DeskMini with an NH-L9a is decently quiet, but definitely not silent. And under load those 92mm Noctuas get rather loud IMO. Fine for a slim 92mm fan, don't get me wrong, but it's not a low rpm 120-140mm fan.
