[citation][nom]vic20[/nom]I agree except for maybe the P4 part.The change from 8086 to 286 was quite the quantum leap. I had a 286 25Mhz and my buddy's XT felt like it was a dinosaur in comparison. 386's with math co-processors and DX 486s were a big change too. Wathching those machines first run X-Wing, Links 386 then Wing Commander 2 was amazing stuff back then.I agree on Pentium Pro too. I had a PPro 180 and it didn't feel any better than a 200mmx, even when I tried NT 4.0 which the RISC/CISC on-CPU cache PPro was supposed to excel in. Hell even the first 233 PIIs which combined the two designs didn't blow me away like the old generation changes did.My Dual PII 333 NT 4 box was probably the first big wow in years. I could watch videos, run a quake II dedicated server minimized, fire up another quake II instance in an OpenGL window and log into the server, while playing MP3s in Winamp with OpenGL visualizations all at the same time with no slowdowns. I laughed when Dual cores became the big "new" thing. Over ten year old workstation idea made new again. Then when Q6600 came out I was reminded of my buddy's really old Quad PPro 200 lolI don't know about P4 though. Sure the first time I built my buddy's 3.06 HT Northwood with a gig of 1066 RDRAM I was very impressed but even a 1.6 Core 2 kicks my old OC'd 3.73 P4's butt in lots of apps. It seems eve if you can get rid of the heat, Netburst can give you high clocks but diminishing returns in performance due to the deep pipeline.[/citation]
The Pentium 4 design didn't work because the decoders were inadequate, as well as other solvable things. IBM did a really good job with the POWER6, which was also a clock speed beast. The problem with the Pentium 4 was, it had only one decoder, and the trace cache was really small, so almost 50% of the time, it was running as a scalar processor.
It had a long pipeline, but don't forget it was double-pumped, so ran twice as fast.
For single threaded apps, a long pipeline with very high clock speeds is the way to go. IPC is great, but there's a point where you just can't get much more out of it. For sheer performance, on one processor, a longer pipelined processor would do better, but the power use/performance would probably go down.