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C`t Throws Athlons And P4s In The Gladiator Pit
An unnamed correspondent writes: "In the most recent C`T "Computer technik" there is a great benchmark with a pentium 4 (1,5 and 1,4 ghz)vs a athlon thunderbird (1,2 ghz and 1,2 ghz ddr memory with the 760 chipset).
If you think that that isn`t a fair race ... then read it now here and here in English.
You should get a copy of the German paper version anyway -- great magazine, even beter benchmark.
Now does anyone know where to get a 760 mainboard ;-)" Unnamed's cousin Noname also contributes a link to GamePC, which
reviews in grand 13-page SE-style the 1.4 and 1.5 GHz P4 chips.
The SPECfp benchmark is a bandwidth hog. The only reason the P4 is faster than the Athlon is because it has a superior memory system. Even a DDR-ified Athlon is not enough. This is not really fair I think. The Athlon has a much faster FPU than the P4 (look at all other FPU benchmarks), but is is much slower at SPECfp. SPECfp is generally made up of huge scientific computation loops, some that were written to be run on supercomputers. This might not be an accurate represenation of floatingpoint programs running on PC:s or workstations. Therefore SPECfp might not be so interesting for most of you. SPECint on the other hand is very representative of common uses of a computer (PC/workstation) and should be looked at more closely.
Some other answers to your question were really uneducated. SPEC is an organisation producing open bechmarks and the whole industry has a saying about the benchmarks. Not just Intel like someone thought.
Hope this sheds some light on the issue.
/peter
A lot of the discrepancy between GHz and performance seen in P4 chips is explainable by Intel's choice of pipeline design. Intel chose to make extraordinarily deep pipelines on the P4 chips, which allows them to crank the clock speed up up up. Sounds great, huh?
The problem is that it's a bit of a false gain. Most of the performance gained in clock speed is lost again to the serious hit you take at each branch misprediction. If you could keep your ultra-long pipe full, you'd be cruising, but you can't. Occasionally you will mispredict, and have to flush that pipe. One your pipe becomes as deep at the P4, that performance hit starts eating your lunch. Suddenly, most of your processor is sitting empty most of the time.
So, clock-for-clock P4's get slaughtered by Athlons or PIII's. But Intel doesn't care. They know that the majority of consumers buy based solely on that magical MHz/GHz number. Most consumers are not sophisticated enough to realize that there is more to performance to clock rate.
This move on Intel's part was motivated by marketing rather than management. They are playing on the uneducated masses. It is all but directly deceptive, and I hope they get their clock cleaned by the press for it.
Buyer beware.
--Lenny
I hope you realize that this is a fundimental CPU design. If AMD wants the Athlon to go beyond 2GHz they will have to make a deeoper pipeline.
:).
...Or move to a finer linewidth.
Pipelining lets you increase the clock rate at a given linewidth. It isn't a requirement for faster clock rates in general.
Sometimes it's a good idea to use a larger pipeline, and sometimes not. For a given linewidth, increasing the pipeline depth will increase the clock speed at the expense of mispredict penalty and hardware complexity and timing sensitivity. Sometimes the increase in clock speed is enough to offset the disadvantages, but beyond a certain point, a deeper pipeline makes performance _worse_. What pipeline depth makes sense depends on your branch predictor, your cache, and a few other things.
However, shrinking linewidth will always let you increase clock speed, regardless of pipeline depth. It gives a straight factor-of-x speedup of all logic, no matter how the pipeline of the chip is set up.
I've been studying this for five years, so I have a good idea of what the tradeoffs are
Its all great to look at benchmarks but a chip that is unavailable scores a 0 each time you test it. There's two reasons a chip is usually unavailable. It is priced well beyond reach and reason or it is being produced in such low quantities that they might as well not make it
Since the release of the Athlon, AMD's chips are more readily available at higher clock speeds. Right now, there are 4 full pages of vendors selling the AMD 1.1 Ghz Thunderbird. The chip sells for as low as $341. That is an available chip.
Intel's 1.4 and 1.5 Ghz chips are available from 8 vendors and will cost you between $950 and $1100. In my book that chip is not available.
Pentium 4 1.5 GHz: $1099 (Pricewatch)
AMD T-Bird 1.2 GHz: $488 (Pricewatch)
Marketing to convince consumers that Pentium 4 is faster: $4 million
Look on Intel managers' face after seeing sales statistics: Priceless
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A picture is worth 500 DWORDS.
So, what you are saying is that for a fair comparison, we should run software optimized for the P4 on both the P4 and Athlon, instead of software optimized for neither.
It's only a level playing field if it's pre-titled in Intel's favor?
There's no "we" in team, only "me"