Are Pentium mobos Turbo-able even?
This guy has a similar PC to yours and couldn't figure out how to do it.
https://ancientelectronics.wordpress.com/2014 … ay-2000-p5-120/
I'd say wait to get into DOS, then hold Ctrl+Alt then start pressing each key on the keyboard (except Del, hehe). You might get lucky and discover the right toggle key... if there ever was one.
Another thing to do probably even before trying, is to trace the Turbo LED connector. If it has a dedicated header on the mobo or if it's branched off some generic LED connector (maybe even PWR LED). In which case it would prove to be a dud Turbo LED.
Turbo XT 12MHz, 8-bit VGA, Dual 360K drives
Intel 386 DX-33, Speedstar 24X, SB 1.5, 1x CD
Intel 486 DX2-66, CL5428 VLB, SBPro 2, 2x CD
Intel Pentium 90, Matrox Millenium 2, SB16, 4x CD
HP Z400, Xeon 3.46GHz, YMF-744, Voodoo3, RTX2080Ti