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?
Hard to say. It had 8MB of RAM, which is plenty for Doom. Its CPU runs at 80MHz–a monstrous clock rate for 1976–but from what I can tell of its architecture, it favors running the same thing on millions of datapoints. Something like how GPUs work now. Doom wasn’t coded for an architecture like that.
Carmack has some remarks about it here (quoted below for avoiding Xhitter): https://twitter.com/ID_AA_Carmack/status/1340794861050605568
"AFAIK, nobody ever ported Doom to run on a Cray 1. The scalar CPU should be fast enough (in 1976!) to draw 320x200, but memory would be an issue because it wasn’t byte addressable – you could only load and store aligned 64 bit values, and a max of 1M elements would be a pinch. "
So that 8MB of RAM sounds like a lot, but it can’t load data very efficiently for less than 64-bit values, and thus it doesn’t go as far as you’d think.