It wasn't just old hardware. Upgrading from SunOS to the early Solaris versions on the same hardware was noticeably slower. 2.4 was the first usable version I

It wasn't just old hardware. Upgrading from SunOS to the early Solaris versions on the same hardware was noticeably slower. 2.4 was the first usable version IMO and it improved a lot by the time 2.6 was out (but then they dropped support for older hardware).