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SPARCstation systems running OpenBSD can be made to blink their power light as a load indicator. The faster the LED blinks, the lower the system load. The slower the LED blinks, the higher the load.
This functionality can be enabled by setting
machdep.led_blink=1in /etc/sysctl.conf and then rebooting the machine.
This has been tested on a SPARCstation IPX by me and SPARCstation 2, 4, 5 by others.