AMD Question?

[Serene Grace]

I've been looking into the different types of processor available (as you do) and I'm seeing the usual crop of Intel and AMD's available. However, I've always been interested to know why the Intel processors seem to have higher GHz than simliar AMDs, but when you see the benchmark tests: they seem to process at similar-ish speeds (Intel tends to be faster, but I expect one CPU with a 2.4 GHz speed to run considerably faster than a CPU with a 1.8GHz speed). I know that the AMD CPUs reduce the fetch execute cycle - is that why the GHz speed is lower? Can somebody explain this to me in a bit more detail? Cheers!

 

[Archer]

I've been looking into the different types of processor available (as you do) and I'm seeing the usual crop of Intel and AMD's available. However, I've always been interested to know why the Intel processors seem to have higher GHz than simliar AMDs, but when you see the benchmark tests: they seem to process at similar-ish speeds (Intel tends to be faster, but I expect one CPU with a 2.4 GHz speed to run considerably faster than a CPU with a 1.8GHz speed). I know that the AMD CPUs reduce the fetch execute cycle - is that why the GHz speed is lower? Can somebody explain this to me in a bit more detail? Cheers!

What you're looking at is called IPC (instructions per cycle). It all depends on the processor design, which has too many factors to mention. In the Pentium 4/Athlon 64 era, AMD's processors had higher IPC, yes. But they don't any more, aside from the Intel Atom/AMD C/E-Series (known as Bobcat), where an AMD C-50 at 1GHz will match a 1.6GHz Dual-Core Atom. The 1.6GHz AMD E-350 will smash them both. What processors are you looking at, specifically?

At the moment, Intel's Core-i series has a MUCH higher IPC than AMD's Bulldozer/FX series. That doesn't automatically make them better, but because they have similar clock speeds in the high end (in the Desktop, ie i7-3770K, AMD FX-8150), the Intel chips are faster in all but the most multi-threaded applications, such as video conversion (ignoring quicksync).

You can still get decent performance from a low IPC chip, such as the Pentium 4 or AMD FX, which is done by having a very high clock-speed (eg, Pentium 4s got up to 3.6GHz and the AMD FX-4170 is 4.2GHz), but this comes at the cost of lots of heat and power - fine in a desktop (reduced overclocking potential aside), but not in a laptop, which is why laptops always run at low clock speeds. The problem for AMD is that Intel's i7-2700K and 3770K run at 3.4 and 3.5 GHz respectively, while maintaining incredibly high IPC. But you pay more for the CPU and motherboard on the Intel platforms, so there's so much to take into account. Plus, 95% of people couldn't tell the difference between two differently performing chips if their life depended on it. Then there's graphics. AMD's A-Series graphics are dramatically faster than anything Intel can offer. But higher-end systems often use dedicated graphics, rendering that irrelevant.

tl;dr - depends on the chip design. Just compare what you're looking at directly in benchmarks of the applications that matter to you. Hope I didn't add more confusion to the mix.

 

[Serene Grace]

What you're looking at is called IPC (instructions per cycle). It all depends on the processor design, which has too many factors to mention. In the Pentium 4/Athlon 64 era, AMD's processors had higher IPC, yes. But they don't any more, aside from the Intel Atom/AMD C/E-Series (known as Bobcat), where an AMD C-50 at 1GHz will match a 1.6GHz Dual-Core Atom. The 1.6GHz AMD E-350 will smash them both. What processors are you looking at, specifically?

At the moment, Intel's Core-i series has a MUCH higher IPC than AMD's Bulldozer/FX series. That doesn't automatically make them better, but because they have similar clock speeds in the high end (in the Desktop, ie i7-3770K, AMD FX-8150), the Intel chips are faster in all but the most multi-threaded applications, such as video conversion (ignoring quicksync).

You can still get decent performance from a low IPC chip, such as the Pentium 4 or AMD FX, which is done by having a very high clock-speed (eg, Pentium 4s got up to 3.6GHz and the AMD FX-4170 is 4.2GHz), but this comes at the cost of lots of heat and power - fine in a desktop (reduced overclocking potential aside), but not in a laptop, which is why laptops always run at low clock speeds. The problem for AMD is that Intel's i7-2700K and 3770K run at 3.4 and 3.5 GHz respectively, while maintaining incredibly high IPC. But you pay more for the CPU and motherboard on the Intel platforms, so there's so much to take into account. Plus, 95% of people couldn't tell the difference between two differently performing chips if their life depended on it. Then there's graphics. AMD's A-Series graphics are dramatically faster than anything Intel can offer. But higher-end systems often use dedicated graphics, rendering that irrelevant.

tl;dr - depends on the chip design. Just compare what you're looking at directly in benchmarks of the applications that matter to you. Hope I didn't add more confusion to the mix.

Sorry for the late-ish reply, I didn't even realise that the thread had been answered until now.

As for your explanation: it was put across very clearly, thank you. I understand a little more about the reason behind the difference in speeds of both chips now. Having now looked into the IPC in a little more detail, I can tell why my AMD A8 1.6GHz runs at a similar speed to an Intel Core i3 350M 2.26GHz.

Also, I didn't quite look into enough detail when comparing the benchmarks for my original two processors (an Intel Core i5 2467M and the A8 3520-M) as it seems that both processors have a base speed of about 1.6GHz, but the clock speed can then be increased to a maximum of 2.5GHz on the AMD and 2.3GHz on the Intel with overclocking as a factor. However I only looked at the base speed for the AMD and the overclock speed for the Intel, which was why there seemed to be such a substantial difference where in reality they both run at similar base and overclock speeds.