Yes the Opterons are locked but like with (almost) all socket 939 CPUs lower multipliers are always available as long as your motherboard lets you change multiplier.
Not having the ability to choose higher multipliers than stock isn't much of an issue if your motherboard lets you change the bus speed. A good San Diego 4000+ will often do 3000+ MHz on a decent board like Asus or DFI nForce4.
New PC: i9 12900K @5GHz all cores @1.2v. MSI PRO Z690-A. 32GB DDR4 3600 CL14. 3070Ti.
Old PC: Dual Xeon X5690@4.6GHz, EVGA SR-2, 48GB DDR3R@2000MHz, Intel X25-M. GTX 980ti.
Older PC: K6-3+ 400@600MHz, PC-Chips M577, 256MB SDRAM, AWE64, Voodoo Banshee.