> I've been testing out both the 8GB Pi 4 and the new Pi 400 overclocked to 2.2 GHz. For many things, both are perfectly adequate.

I wonder if I'm doing something wrong. I have a 4GiB pi 4B and have found it laggy enough to be basically completely unsuitable for even the most lightweight interactive computing tasks, e.g. basic (ad filtered) web browsing. I think there might have been a bit of intermittent laginess in typing into an xterm in a bare bones tiling window manager with basically nothing else going on, but I'd have to check again. After the initial hickup on full-screening, did the video play back properly for you? For me it was not possible to play 480p youtube videos.

All in all this was much worse than I expected from a quad core machine with 4GiB.

Now I haven't got the fastest micro-SD card, and I'm running with Ubuntu 20.04 64bit server rather than raspian, but is this just what I should expect, or should a different configuration of the 4GiB 4B handle light web surfing and fullscreen video playback?

Ive read multiple reports that the Ubuntu distrivution is significantly slower than the Raspian bundle. I dont know the root cause, but you could check out the stock image for a comparison yourself

How do you actually run compute modules (I assume that's your 'CM' abbreviation above)? Do you need a custom "rack" or something? If so, where do you get them?

Either design your own carrier board or use https://www.raspberrypi.org/products/compute-module-4-io-boa...

Bummer. I would pay good money for a single board that let me mount 4-8 of these guys. I'm aware that the Turing Pi 2 will supposedly do this, but it's still in development.

The CM4 is still a very new product, I know of at least a few other projects that are still on the drawing board. Give it time, I think we'll see some creative adaptations.

For now I'm just using the IO board, and I have a couple more on the way, and I'll rack them up using M2.5 spacers.

Can you list the other projects? What are the advantages of racking CM4s + IO boards vs racking RPI4s? Is it just the extra bit of compute power? In my mind, the biggest draw to the CMs is the prospect of putting them all on one board without having to run cables to each, especially since there aren't multiport USB-C power supplies available that can power multiple RPI4s. Another advantage is the prospect of faster SSD communication.

One of these things stand out. Making a video should take one or two frames. (Milliseconds.)

Something is very wrong with the state of software and GUI. There is nothing inherently slow about making a video full screen, but I understand there is something in todays software pipeline making this a bottleneck.

The Rpi4 plays 720p video full screen at 5% cpu usage (because it has hardware decoding support) - using omxplayer. The hard part is for the hardware decoding support to be enabled in the right places and it seems like kodi is the only place (mpv, vlc don't do it by default)

The other missing piece for the transition to fullscreen is a robust compositor API, such that the same compositional layer can just have its size changed rather than going from app-compositor to system-composited in a new window. Something like, say, Wayland. <insert that whole debate/debacle here>

It absolutely should only take a couple of frames to make a video fullscreen, but to put things into perspective, on my 2015 macbook it takes 3-4 seconds to toggle fullscreen on youtube, and my much more powerful linux desktop isn't much faster.

Have you considered that the compression algorithms for video are nontrivial? I mean I'm sure there can be dedicated hardware for video decoding, but would you put that in a low-cost, low-energy entry-level CPU where you want to shave off as much cost in favor of flexibility?

The Pi is not primarily intended for media consumption. That said, for a similar price to a RPI + display you can get a cheap tablet that will (should?) have dedicated video hardware.

The original Pi CPU was intended for media consumption in set-top-boxes; it was a huge video core with a small ARM on the side.

It has had hardware video decompression for multiple revisions.

In fact it had H264 decoding in all revisions, optional unlockable MPEG2 and VC1(?) up to and including all Pi3 models and H265 since the Pi4.

The regular Pi 4 can run at 2.2 GHz? With external cooling I assume.

Pi 400 is the one with the keyboard and has built in soft-cooling. I wonder what a Raspberry Pi overclocking competition would do.

Look into top end GPU or CPU overclocking on the desktop side of things if you want to know where RPI overclocking would end up. It's going to be the same general thing - get it as cold as possible and ram as much power & voltage as possible as cleanly as possible. It wouldn't end up looking anything like a Raspberry Pi at the end of the day, though, as the first step would be replacing the entire power delivery system (see for example products like https://www.evga.com/articles/01140/evga-epower-v/ on the extreme GPU side of things)

So far no matter what I've tried I can't get beyond 2200 MHz.