Comment by Maxious

In Schneider's 1995 book he estimated factoring a 512-bit number would take roughly 30,000 MIPS-years (a one-million-instruction-per-second computer running for one year).

When a research team actually factored RSA-155 in August 1999, it took 8,400 MIPS-years due to efficiencies discovered. It still took 35 CPU-years spread across a cluster of 300 fast SGI/SUN workstations and Pentium II PCs (400-500 MIPS each), crunching in parallel for seven months. https://cs.ccsu.edu/~pelletie/local/risks/cryptography/Facto...

Robert Silverman, a senior research scientist at RSA Laboratories, published an analysis projecting these new hardware requirements against Moore's Law. His expectation was that within 10 years (roughly 2009–2010), common desktop machines would possess the speed and memory necessary to handle a 512-bit factorization entirely on their own. https://cr.yp.to/bib/2000/silverman.pdf