I'm not very much against OC Detective. Austin was where I first got this info from, btw. What first gave me a heads up about the third letter being significant were the GameVe DLT3C's. Unlike the ones from Excal and Svc, these were nothing spectacular at all. They did about as well, if not worse as a DUT3C, maxing out at 2.2-2.3 on air, 200mhz or more below the DLT3C's. The only thing that looked odd in their stepping codes were the third letter- TPXW. I have seen TPMW's, and they do just as well as any other DLT3C. But these X's were clearly worse. There was a huge thread on amdmb.com about them, and all of them did rather poorly in comparison to other DLT3C's. One of the best Barton steppings was the AQUCA XPAW. Most that you see these days are AQXCA XPMW's, and they do not seem to do as well. IF you look on the Vr-zone lists of the best overclockers of both Bartons and T-Breds, the front pages are dominated by processors of several stock speeds, but almost all having their third letter as A's, B's and C's. I'll do some more searching, but for now that's the best I've got. Basically, I've been hunting down the 4 letter codes, and I can't draw any conclusions about any of the letters in it from own findings except for the third letters. TPMW's, UPMW's, VPMW's, WPMW's and XPMW's all perform the same, but an XPAW's seem to be better than XPMW's within the same processor type. All 1700+'s are xPMW's, so we can't say anything for sure about them, but within Barton 2500+'s, xPAW's appear to be better than xPMW's. The difference between A and M appears to be negligible at most, though, but the difference between an M and an S or X is rather large.