AMD vs Intel: CPU Design Philosophy

Johan writes "We have published an in depth comparison between the CPU design decisions that AMD's engineers (Athlon and upcoming Mustang) made and those of Intel's engineers (Pentium 4). Some of the questions answered: Are double pumped, hyperpipelined, low latency designs the only future for x86? Will future designs from AMD and other competitors be similar to Intel's innovative seventh generation core? "

Comments

Intel is going the clock speed route for a reason

[Xevion]

Intel is going the clock speed route for a reason, and it is pretty clear to me. While a 1.4Ghz PIII or Thunderbird may be a good deal faster then a 1.4Ghz P4, the P4 will be avalible at significantly higher clock speeds (2Ghz planned in Q4 2001 I believe) because of its hyper-pipelined design. Also, Intel will be able to (Hopefully from Intel's business perspective) charge obscene amouts of money for these CPUs because their clock speeds are so high.

Intel, however, is truly making an innovative processor design with the P4. The speed of electricity is possibly becoming a bottleneck (As the 2 "drive" stages in the pipe Ace's pointed out as possibly being for the signal to reach the other side of the chip) The only problem with this is that AMD has caught up extremely quickly in the past year, and while imperfect, the Athlon design scales in clock speed extremely well. With the 1.2Ghz Thunderbird here, on a .18 micron process, no less, as long as AMD can keep up with the process technology they will stay in the high end market.

The P4 uses about twice as many transistors as a Thunderbird or Coppermine, in order to achieve the massive hyper-pipelined design that they have. AMD on the other hand, with Sledgehammer, will integrate 2 CPU cores onto one die with a shared L2 cache. I would imagine that the design for Sledgehammer is similar to the Athlon, but with 64 bit extensions. Why not use what technology they have and refine it instead of reiinventing the weel?

IBM, with Blue Gene, is taking this parallelism to an extreme (Quote at bottom of my post is directly off of IBM's site), and AMD is taking a similar route on a much smaller scale. Now think of the potential performance difference between a P4 1.5Ghz and a 1.2Ghz Thunderbird given that the P4 is slower at the same clock speed. Almost no perceptible performance difference, in all likelyhood. Now imagine a dual 1.2Ghz thunderbird, and imagine how that would perform in comparison: yes, all of the systems are extremely fast, but the "dual" system would stand out as the fastest. Take into consideration that the die size for Sledgehammer won't be much more then what it is for the P4. So, you will be able to get a dual-cored CPU for around the same price as a single cored CPU that gets lower IPC and runs at a higher clock speed.

As you can see, there will be no comprison for Sledgehammer on the desktop as long as there is enough memory bandwidth to satisfy its needs.

• Blue Gene will consist of more than one million processors, each capable of one billion operations per second (1 gigaflop). Thirty-two of these ultra-fast processors will be placed on a single chip (32 gigaflops). A compact two-foot by two-foot board containing 64 of these chips will be capable of 2 teraflops, making it as powerful as the 8000-square foot ASCI computers.

  Eight of these boards will be placed in 6-foot-high racks (16 teraflops), and the final machine (less than 2000 sq. ft.) will consist of 64 racks linked together to achieve the one petaflop performance..."

Re:You are the idiot (please mod up)

[ToLu the Happy Furby]

When the P6 was released, it was the fastest processor available in industry standard benchmarks (SPEC, including Alpha). Its design was highly original, and manages to keep the CISC nastiness contained to the first few stages of the pipe. Claiming that the P6 was not a world-class design when released is only a testament to your own ignorance.

Exactly correct. If I had moderator points, they'd be yours.

And indeed, the 1 GHz P3--on that same, 5 year old P6 core--is still tied with the moderately-vaunted brand-new mucho-expensive (not available until Q1) 900 MHz UltraSparcIII in SPECint2000. The 1.2 GHz Athlon would presumably perform even better (once they release SPEC scores from the new Compaq Fortran compilers), making it second only to the fastest (and also none-too-available) Alphas in terms of pure performance. The x86 ISA may be suboptimal, but Intel and now AMD have been able to keep up with the best--and most expensive--of the RISC world due to superior engineering (except when compared to the excellent Alpha team) and superior process technology. Sure they may not have the i/o bandwidth, RAS, or operating systems to compete in the big leagues, but anyone dissing today's x86 chips on account of their designs or engineering qualities is, as the poster said, demonstrating their ignorance.

And if Compaq doesn't hurry the EV68 (die-shrunk Alpha) to market, the P4 and perhaps Mustang as well will blow by even the mighty Alpha, in SPECint and possibly even SPECfp. (The last real knock against the x86 ISA is that it is saddled with the horrendous x87 fp architecture, which is why x86 SPECfp scores trail everyone else by so much. With the P4's upcoming SSE2 instructions, however, that problem may be in the past.) Aesthetics aside, there is no doubt that x86 processors, taken as a whole, are easily the best designed, highest performing MPU's around.

Re:Semi-ontopic

[barleyguy]

Actually, when the 760MP chipset comes out from AMD, you'll be able to use 2 different speed processors on the same board.

It's point-to-point multiprocessing, instead of symmetrical. You can, for example, buy a 760MP with a 1Ghz CPU now, and put on a 1.2Ghz as the second processor later. And each chip has it's own Northbridge and path to ram, as opposed to the shared GTL bus on an Intel.

They FINALLY demonstrated the prototypes, so the real boards should be out Real Soon Now.