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: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.