BigDumbDinosaur wrote:
Something Mr. e2020 should think about is just what is getting accomplished at 3000 MHz. While the MPU core may be running that fast, the buses and memory subsystem are not. A contributing factor to the 65xx family's efficiency is the fact that the address and data buses are synchronous to the MPU clock, not a submultiple of it. If an AMD Athlon II system running at 3000 MHz were slowed down to 200 MHz, with a corresponding reduction in bus and memory subsystem speed, it wouldn't produce the throughput of a 65xx system running at the same clock rate
What an utter load of rubbish. Slow an Athlon II (Representative ~3GHz, with 2.1Ghz DDR3) down to 200Mhz and its memory bus will still be running at 70MHz. This is a DDR3 memory bus runs double pumped, so thats 140MT/s. An Athlon II has a dual channel memory controller, so is capable of moving 16 bytes in a single transaction, bringing things to 2240MB/s peak. Average bus efficiency is 80% of theoretical, so practical bandwidth is 1792MB/s. Never mind the multiple layers of cache, so operations which hit the level 1 cache are as fast as RAM... and the Athlon's L1 cache is probably
Now lets move to the processor. Lets say we are dealing with a single core Athlon II for a minute... We are still talking about a three way superscalar architecture with an 128-Bit SIMD unit. This means that, on appropriate code, you can do two integer operations and 4 floating point operations. Most of these operations are single cycle, and those which aren't are relatively complex (i.e. do a lot) anyway. I don't think anyone can argue that a single 6502 instruction has anywhere near the capability of even one floating point single precision add.
I do low level development and optimization on a variety of architectures, and I despise the ugliness of x86, but nobody can successfully argue that Intel and AMD haven't made x86 fly. I think just about the only processor architectures which have been made to go faster are IBM System/Z (The z196 CPU is clocked at an amazing 5.6Ghz) and IBM POWER (Which is clocked very close these days)... which just goes to show, anything will go fast if you throw money at it.
(I realise this thread is old(ish), but I have been away for a while and am catching up)