<a href="https://en.wikipedia.org/wiki/CDC_7600" rel="nofollow">https://en.wikipedia.org/wiki/CDC_7600</a> could handle 10-36 MFLOPS in 1970, which is about an iPhone 4.<p>The Elbrus 2, which was the first Soviet supercomputer, didn't come until 1977. Earlier systems, like the BESM, were mainframes - designed more for data handling than compute power. It looks like 355 BESM-6:s were made, ending in 1987. There were also Minsk mainframes.<p>There were also clones of US hardware, like the ES EVM clone of the IBM 360 (production didn't start until 1972), and PDP-11/VAX clones. Those were after 1970.<p>I'll use 50 BESM-6:s as my shot-in-the-dark estimate. Those seemed to be 1 megaflop (see <a href="https://en.wikipedia.org/wiki/BESM" rel="nofollow">https://en.wikipedia.org/wiki/BESM</a> ), so the USSR could probably do about 50 MFLOPS in 1970.<p>Or no more than three iPhones.<p>For 1985 it's much harder to even guess. Is it even reasonable to include the aggregate sum of the microcomputers of that era? Not if you want to simulate an H-bomb. Only you can answer that.