Difference in AMD 64 CPU speed

[CDC Mail Guy]

To a lot of you this will be a stupid question and I almost hesitate to ask it, but...

What is REALLY the difference in speed between an AMD 64 processor (ie AMD 64 4400+ at 2.2GHz) and a (AMD XP 3200+ at 2.2GHz)? Does the real speed come in the FSB of the chip? I warned that these were stupid questions...Also (1 more) Does a 64 chip process nomal 32 bit applications twice as fast? Thanx for letting me ask.

 

[t3h l337 n3wb]

The architecture of an Athlon 64 and an Athlon XP are very different. It's like comparing a Pentium 4 to a Pentium III or something. 64-bit support just means that the CPU will support 64-bit programs, which haven't been released yet. It doesn't mean it's 2x as fast.

 

[batmanuel]

In your example of the XP 3200+ and the A64 X2 4400+ the PR ratings differences boild down to a few things:

1. The 4400+ is a dual core processor, so it can run two software threads simultaneously while the XP 3200+ can only process one at a time. In a appplication that runs multiple threads like Photoshop, it will be almost twice as fast as a single processor of similar design and clockspeed. Also, it will run a bit faster and smoother when you are running multiple applications at the same time.

2. On-die memory controller for the A64. This allows the processor to talk to the RAM much faster than a XP 3200+ processor that has to communicate to a external memory controller via a frontside bus, which removes a major bottleneck for the processor.

3. More cache. The X2 4400+ has 1MB of cache vs. the 512KB for a XP 3200+. The cache memory runs a lot faster than the RAM, so the more data the processor can hold in cache, the more time it can shave off of computations.

4. SSE2 and SSE3 instructions on the A64 X2. Intel invented SSE2 and SSE3 code optimizations that provides properly software written with fast ways to do certain operations (mainly these shortcuts are used in multimedia encoding apps) and the A64 fully supports these optimizations unlike the Athlon Xp which only can handle the first set of SSE instructions. In certain situations, it will result in the Athlon XP to run a program much more slowly than a late model Athlon 64 that can use those new code optimizations.

 

[imported_Kensai]

Originally posted by: batmanuel
In your example of the XP 3200+ and the A64 X2 4400+ the PR ratings differences boild down to a few things:

1. The 4400+ is a dual core processor, so it can run two software threads simultaneously while the XP 3200+ can only process one at a time. In a appplication that runs multiple threads like Photoshop, it will be almost twice as fast as a single processor of similar design and clockspeed. Also, it will run a bit faster and smoother when you are running multiple applications at the same time.

2. On-die memory controller for the A64. This allows the processor to talk to the RAM much faster than a XP 3200+ processor that has to communicate to a external memory controller via a frontside bus, which removes a major bottleneck for the processor.

3. More cache. The X2 4400+ has 1MB of cache vs. the 512MB for a XP 3200+. The cache memory runs a lot faster than the RAM, so the more data the processor can hold in cache, the more time it can shave off of computations.

4. SSE2 and SSE3 instructions on the A64 X2. Intel invented SSE2 and SSE3 code optimizations that provides properly software written with fast ways to do certain operations (mainly these shortcuts are used in multimedia encoding apps) and the A64 fully supports these optimizations unlike the Athlon Xp which only can handle the first set of SSE instructions. In certain situations, it will result in the Athlon XP to run a program much more slowly than a late model Athlon 64 that can use those new code optimizations.

What he said... I want a chip with 512MB cache!

 

[Bona Fide]

Originally posted by: Kensai

Originally posted by: batmanuel
In your example of the XP 3200+ and the A64 X2 4400+ the PR ratings differences boild down to a few things:

1. The 4400+ is a dual core processor, so it can run two software threads simultaneously while the XP 3200+ can only process one at a time. In a appplication that runs multiple threads like Photoshop, it will be almost twice as fast as a single processor of similar design and clockspeed. Also, it will run a bit faster and smoother when you are running multiple applications at the same time.

2. On-die memory controller for the A64. This allows the processor to talk to the RAM much faster than a XP 3200+ processor that has to communicate to a external memory controller via a frontside bus, which removes a major bottleneck for the processor.

3. More cache. The X2 4400+ has 1MB of cache vs. the 512MB for a XP 3200+. The cache memory runs a lot faster than the RAM, so the more data the processor can hold in cache, the more time it can shave off of computations.

4. SSE2 and SSE3 instructions on the A64 X2. Intel invented SSE2 and SSE3 code optimizations that provides properly software written with fast ways to do certain operations (mainly these shortcuts are used in multimedia encoding apps) and the A64 fully supports these optimizations unlike the Athlon Xp which only can handle the first set of SSE instructions. In certain situations, it will result in the Athlon XP to run a program much more slowly than a late model Athlon 64 that can use those new code optimizations.

What he said... I want a chip with 512MB cache!

Shotgun!

 

[batmanuel]

Originally posted by: Kensai

What he said... I want a chip with 512MB cache!

Duh. Edited post to fix. Good catch.

 

[CDC Mail Guy]

Thank you for the very easy to understand explainations, as well as nobody calling me stupid! lol. I greatly appreciate the (as usual) help here at AnandTech.