From an evaluation by Roy Longbottom, this interesting observation:
In 1978, the Cray 1 supercomputer cost $7 Million, weighed 10,500 pounds and had a 115 kilowatt power supply. It was, by far, the fastest computer in the world. The Raspberry Pi costs around $70 (CPU board, case, power supply, SD card), weighs a few ounces, uses a 5 watt power supply and is more than 4.5 times faster than the Cray 1.
That’s surprisingly powerful for the Cray. So it could have probably ran Doom?
Its strength was in running the same operation on large sets of data rather than general purpose computing. So specialist hardware would need to be developed for real time input and a graphical display (which would need to be able to draw the screen from the data the Cray produced. )
I think a better comparison would be a modern GPU.
A Cray 1 could do approx 160,000,000 floating point operations per second. A modern GPU can do 1,600,000,000,000 per second.
If I’m reading that right, it’s 2 orders of magnitude greater? (Math is not my strong suit)