<< Still, the success of the K6-x demonstrated that Socket7 had just as much potential for high performance CPU design as Slot1/Socket8/GTL+ did. >>
I guess my first rebuttal is to turn your arguement on it's side: if socket 7 was so great, then why did AMD abandon it in favor of the EV6 bus? When they did that they left Cyrix and Winchip behind while they used DEC's proprietary bus interface. Clearly AMD could have continued to move the K6-2 forward into 0.18um technology and they probably could have ramped it substantially faster - there was plenty of technology headroom beyond. Like you said, AMD could have raised the frequency to 133MHz (well, I disagree with this, but let's assume this is true) and improved the processor and been competitive.
And eventually, when they wanted to move forward in technlogy, they should have used an open specification so that everyone could have competed together. They should have spent a lot of money and time and engineering effort and released it freely (like, for example, Intel and USB and PCI) so that Winchip and Cyrix could compete effectively with them. Modus, you seem to be argueing that technology shouldn't move forward and that, if it does, and I invent a better way to do something then I really should give it away freely so that my competition can use the fruits of my labors to compete better with me.
If socket 7 is so wonderful, why didn't AMD put the Athlon on the super7/socket7 platform?
If the slot 1 design was purely a move designed to shake off the competition, then why did AMD create slot A?
But these questions aren't really a good arguement in favor why a newer bus - or even a different socket or slot - was needed. First off there's the greatly increased power requirements of current processors. We have dramatically cut the voltage (from ~3V to ~1.7V)), while dramatically increasing the current (because power is higher now than it was back then when we had the higher voltage). This mandates more power pins to avoid huge IR drops. But If you add pins to a socket, it's not really the same socket anymore.
Second, I'm nearly certain that the signalling technlogy used in socket 7 couldn't run much faster than 100MHz. IIRC, the low voltage levels of Gunning Transceiver Logic (GTL) are required for high frequency operation on a PCB. In GTL+ the signals use center termination to a fixed reference voltage (1.5V) and swing from there, this minimizes noise on the PCB. I don't think that you could achieve anywhere near 133MHz using the logic the (IIRC) TTL logic used on the older socket. I have a clear idea of how the Pentium Pro/Pentium II/Pentium III bus works, but I don't quite recall how the Pentium bus worked (it's been too long). But I feel confident that if it could have run at 133MHz, then someone would have ramped it up there. I think they needed to switch the voltage levels and the logic swing in order to get it above 100MHz.
So, my point is that I think it would be impossible to put an Athlon or a Pentium III on the old socket 7 bus without a substantial bandwidth cut and without a dramatic redesign of the power consumption(to get it below ~10W).
But discussions of older technology being propped up to avoid incompatibility ignore the fact that the computer revolution is built on finding newer, and nearly always better, ways of doing things. We probably could have really fast 500MHz 486's nowadays if everyone continued to ramp the 486 core down in 0.25um and 0.18um processes. But instead we use much faster (and larger and more complex) superscalar cores running at 1GHz+. Sure, we abandoned the 33MHz 486 186-pin Socket 6 socket in favor of the much faster, and that messed things up for a while, but the newer sockets are both necessary (for power) and higher bandwidth.