June 22nd, 2014

Feasibility of desktop on ARM cpu

Thinkpad X60 is old, Core Duo@1.8GHz, 2GB RAM notebook. But it is still pretty usable desktop machine, as long as Gnome2 is used, number of Chromium tabs does not grow "unreasonable", and development is not attempted there. But eats a bit too much power.

OLPC 1.75 is ARM v7@0.8GHz, .5GB RAM. According to my tests, it should be equivalent to Core Solo@0.43GHz. Would that make an usable desktop?

Socrates is dual ARM v7@1.5GHz, 1GB RAM. It should be equivalent to Core Duo@0.67GHz. Oh, and I'd have to connect display over USB. Would that be usable?

Ok, lets try. "nosmp mem=512M" makes thinkpad not boot. "nosmp mem=512M@1G" works a bit better. 26 chromium tabs make machine unusable: mouse lags, and system is so overloaded that X fails to
interpret keystrokes correctly. (Or maybe X and input subsystem sucks so much that it fails to interpret input correctly on moderate system load?)

I limited CPU clock to 1GHz; that's as low as thinkpad can go:
/sys/devices/system/cpu/cpu0/cpufreq# echo 1000000 > scaling_max_freq

Machine feels slightly slower, but usable as long as chromium is stopped. Even video playback is usable at SD resolution.

With limited number of tabs (7), situation is better, but single complex tab (facebook) still makes machine swap and unusable. And... slow CPU makes "unresponsive tabs" pop up way too often.

Impressions so far: Socrates CPU might be enough for marginally-usable desktop. 512MB RAM definitely is not. Will retry with 1GB one day.