And the compilation speed difference wouldn't be small. The HP workstations they were using were "entry level" systems with (at max spec) a 100MHz CPU. Their Alpha server had four CPUs running at probably 275MHz. I know which system I would choose for compiles.
I never had cause to build quake, but my Linux kernel builds took something like 3-4 hours on an i486. It was a bit better on the dual socket pentium I had at work, but it was still painfully slow.
I specifically remember setting up gcc cross toolchains to build Linux binaries on our big iron ultrasparc machines because the performance difference was so huge — more CPUs, much faster disks, and lots more RAM.
That gap disappeared pretty quickly as we headed into the 2000s, but in 1997 it was still very large.