Replies to post #3228 on Advanced Micro Devices Inc (AMD)

[fyodor]

Dan3: Banias is a new PIII core stepping

That's one heck of a understatement.

with a wider, faster FSB, SSE2, 1 meg of cache, and substantially improved power management.

You're forgetting doubled L1 cache, prefetching and improved branch prediction. Likely many other enhancements as well, but without a thorough test of the processor, it's hard to tell.

It's a good chip (the PIII was a superbly balanced core) but the PIII core has had trouble keeping up with the Athlon core, in the past.

In terms of frequency scaling, yes, that is true. However, the PIII CuMine was slightly faster than Athlon Tbird per clock in non-scientific applications (although significantly slower in x87 double precision floating point math).

Since then, AMD has improved branch prediction, added prefetching, more L2 cache and increased the FSB. With Banias, so has Intel! Plus a lot more.

Let's look at the frequency scaling again. Right now, Banias is at 1.6GHz @ a Vcc of 1.48V. That, in itself, seems pretty impressive. The Vcc(max) for the processor, however, is specified at 1.75V. In other words, there seems to be plenty of voltage headroom which could be used (if needed at all) to reach AthlonXP speeds.

All in all, what you have is a chip that:

- Appears to scale [in frequency] as well as Barton.
- Is almost certainly significantly faster per clock than Barton in CPU-limited instances (the sole exception being DP x87).
- Uses the P4 bus, so getting it to run on an i875P with dual DDR400 should be a minor issue.

Now, please remember that the transistors and layout of same in Banias are optimized for *low power*, not *performance*. Using the same leading-edge process (incl. transistors and layout) with which the P4 is made, Banias could almost certainly scale quite well.

I haven't been able to dig up much in the way of detailed information on the Banias, but I suspect that Intel may have substially increased the pipeline length. This would help explain why the chip reaches 1.6GHz at a relatively modest voltage, whereas the older PIIIs had problems keeping up with the Athlon.

-fyo