Intel Q9450 vs Phenom 9850 - ATI HD3870 X2

[gosh]

Gosh --
This thread is about debunking your assertion that the FSB is crippling Intel in high resolution gaming. Comparing two processors is a different topic all together, and it is widely shown and been sufficiently demonstrated that Intel currently produces the superior part. This does not make the Phenom (Agena or Barcelona) a bad processor, it is a good processor.

In terms of good game play, this criteria simply resides in the ability of the HW to produce frame rates such that the minimum is above the refresh rate of the monitor.

Your post here http://www.xtremesystems.org/forums/...2&postcount=17 is what is at issue. Nobody, not even me, will argue that the FSB implementation is not old and antiquated, however for client desktop applications it is not the critical factor you are asserting.

Intel and AMD take two approaches to feeding the core(s) with instruction or data from system memory -- a fast memory access will smaller cache or a large cache with slower access to memory. Intel has designed and implemented a caching system that works around the FSB deficiencies compared to AMD's IMC approach.

It works like this ....

When a processor crunches data and instructions it fetches that information into the queue. Those instructions proceed through a general progression fetch, decode, reorder, execute and retire. As it moves through the fetch buffer and requires the next block, it goes to cache first if it is there it generates a cache hit, if it is not there it is a cache miss. The hit rate for Intel cache is higher than it is for AMD cache, due to size and a few other variables.

The miss rate on cache is directly proportional to the size, the large the size the lower the miss rate. Each cache miss generates a penalty for going to main memory in which case the processor needs to wait X cycles for that data. Intel also has more aggressive prefetchers which are working to populate the cache with the next needed instruction to avoid misses that would require the FSB.

AMD generates > misses than Intel does, but each miss has less penalty. So which is better, a fast memory connection with high miss rates or a slower memory connection with low miss rates. Overall each approach accomplishes the same thing, and considering the body of data on the net showing clock for clock Intel significantly outperforming AMD in most any application then it is sufficient to conclude that Intel's archaic FSB technology is not a problem.

Where the FSB does become a problem is when the workload and memory footprint exceeds the capacity to keep the cache miss rate low... this is the case for high throughput applications found in both server and HPC applications. In cases where BW is the limiter AMD will win, in CPU bound workloads Intel will win. DT is all CPU bound workloads, BW is hardly a factor, I have found only a handful of cases where I could point to the BW of the FSB the culprit.

Now you are talking!

some tiny notes...
How the system design works depends on the application. You can’t say that one big cache has that hit rate and another cache has another. The hit rate depends on the application. Small caches have rather large hit rates. I think that you will see very high hit rates even for tiny caches in most applications. But the performance penalty going to memory is very big for some system design so they are using VERY large caches
Running more applications will degrade advantages for caches pretty fast. Of course you will always ses much speed improvements having caches even if the number of threads is huge.
The exception from this is applications that isn’t using that much memory and have controlled tasks. Applications heavy on calculations etc