Branch prediction works with both revisions of the Cyrix 5x86 in DOS. Stepping 0, Revision 5 is pseudo-stable with branch prediction in Windows. The stability also seems frequency-dependent. The talk has beent hat Stepping 1, Revision 3 is stable in Windows, however I have yet to perform a detailed study for this case. It could also be that some work with branch prediction, and some do not. A lot of the special features are frequency-dependent, especially at 133 MHz.
When I say the '486', I mean the fastest non-Pentium chip, whatever it may be, which functions properly in a socket 2/3 motherboard. This definition varies largely by the individual user and it is the one I have adapted for myself. You all may decide on your own definition.
PARKE: Some Socket 370 CPU clips have 3 mounting holes per side of the clip. These can be used in 2-pronged (per-side) socket 3 motherboards. You can also use a Z-clip CPU clip. As an update to post, I was unable to get a Cyrix 5x86 running stable in Windows at 150 MHz. DOS was stable for awhile, but once the chip heats up, it starts to fail after some time. At 150 MHz, I had to use 4.0 V on a QFP IBM 5x86-100.
Plan your life wisely, you'll be dead before you know it.