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Performance in Synthetic Benchmarks: Cache and Memory Speed

The major participants of our today’s test session, AMD Athlon 64 FX and Intel Pentium 4 Extreme Edition, are new solutions from the architectural point of view, especially in terms of work with the memory subsystem. That is why we decided to investigate their bandwidths and memory subsystem latencies first. For this purpose we used Cache Burst 32 utility, which is a worthy optimization of the traditional Cachemem:

The graphs you have just seen above show very illustratively all highs of the new processor architectures, telling on the memory subsystem performance. You can see the inclusive L3 cache of the Pentium 4 Extreme Edition with a pretty good bandwidth. You can also see the larger 1MB L2 cache of Athlon 64 FX processor here. The results also show very clearly that the integrated dual-channel memory controller of the Athlon 64 FX processor allows it to work with the memory as fast as the memory controller of the i875P chipset used by the regular Pentium 4 CPUs. However, these are pretty logical results, which we have expected to see.

However, there are a few really unexpected things, which I would like to point out. First, we can see that L2 cache of Athlon 64 FX processor is working faster than that of Athlon XP. It proves the fact that AMD did broaden the bus between the processor core and the L2 cache up to 128bit. Moreover, according to more indepth benchmarks, there is a bi-directional bus (64bits in each direction). Also note that the L1 cache bandwidth by Athlon 64 FX and Athlon XP processors appears higher than that of Pentium 4. However, L1 cache of the Pentium 4 processor is remarkable fore a different feature: very low latency, which efficiency we will see later in this article. As for the L2 caches, Pentium 4 processor wins in terms of the bandwidth rates here, which is not at all surprising keeping in mind that this cache has a 256bit bus. The bandwidth of the L3 cache in Pentium 4 Extreme Edition processor is close to that of the L2 cache in Athlon XP, which indicates that there is a 64bit bus used to connect the processor core of the Pentium 4 Extreme Edition

with the L3 cache. By the way, Prescott dies will have a broader bus here. And finally the most interesting thing: the use of larger L3 cache allows Pentium 4 Extreme Edition to speed up writing into the memory proven by the benchmarks results.

For easier comparative analysis, we summed up all the numbers in a table below:

 

Pentium 4 3.2

Pentium 4 3.2 EE (2MB L3)

Athlon XP 3200+

Athlon 64 FX-51

L1 cache read speed, MB/s

23108

23295

26309

29260

L2 cache read speed, MB/s

12915

12920

6667

10145

L3 cache read speed, MB/s

 

6522

 

 

Memory read speed, MB/s

3699

3686

1778

3436

L1 cache write speed, MB/s

10793

10789

16424

16431

L2 cache write speed, MB/s

10802

10799

6512

8293

L3 cache write speed, MB/s

 

7236

 

 

Memory write speed, MB/s

1416

2142

1226

2314

 
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