Socket-A Chipset Comparison - April 2001

Memory Bandwidth - SiSoft Sandra 2001

The first thing we notice here is that the ALi MAGiK1 actually offers a little over 3% more memory bandwidth than the AMD 760 when both are equipped with PC2100 DDR SDRAM.  Remember that translating these numbers into real world performance is difficult simply because the performance increase PC2100 memory offers over PC133 SDRAM is generally less than 10%, in spite of a 100% increase in memory bandwidth; it is highly unlikely that we'll see this 3% advantage creep up in the upcoming tests, however it is interesting to note.

What is even more interesting to point out is that according to this benchmark, the effective memory bandwidth offered by the KT133A's PC133 subsystem is capable of delivering 95% of the usable bandwidth of the AMD 760's PC2100 subsystem.  This is in line with what we saw from our Linpack performance benchmarks, which showed that the KT133A with PC133 SDRAM was able to deliver 96% of the performance of the AMD 760 with PC2100 DDR SDRAM.

After those top three solutions the drop off is significant.  All of the 100MHz DDR FSB ALi solutions are providing bandwidth levels we would expect from i815 or i820 platforms.  You should keep that in mind as we investigate performance moving forward.  What is interesting is that the MAGiK1, when coupled with PC1600 DDR SDRAM, isn't even able to offer more bandwidth than the KT133/A running with PC100 SDRAM.  It seems that with DDR SDRAM, PC2100 is a must as PC1600 is barely able to cut it; at least from a theoretical standpoint.

There is a bit of a change in the FPU-STREAM bandwidth test that is a part of Sandra 2001.  The Sandra 2001 memory test is based on the STREAM benchmark core, and works by performing memory reads and writes while also manipulating the data being read from and written to memory. 

In the case of the FPU performance test, the manipulation is in the form of floating point calculations, which are inherently more memory bandwidth intensive hence, the increase in bandwidth utilization over the integer test.

Here the AMD 760 with PC2100 DDR manages to offer a 5% bandwidth advantage over the MAGiK with the same configuration.  As we mentioned before, it is doubtful that such a small difference in memory bandwidth will translate into much difference in many of the real world performance tests you're about to see.  Again, it is worth noting since there are some, albeit limited, cases where applications are so memory bandwidth limited that small differences like this can actually come into play. 

Interestingly enough, the AMD 760 paired up with PC1600 DDR SDRAM is actually able to offer more bandwidth than the KT133A w/ PC133 SDRAM.  While this makes sense theoretically, it is the opposite of what we have seen in the previous Sandra test.  This also makes proof of the point that the 133MHz DDR FSB isn't necessarily the cause of the superb performance we've seen from the KT133A platform as the third place performer here is running on a 100MHz DDR FSB.  When you think about it, this makes quite a bit of sense, as the DDR EV6 bus is capable of offering more than enough bandwidth for the Athlon's current needs.  But there isn't a question about it that an Athlon running at 1000/133 on the KT133A is noticeably faster than the same CPU running at 1000/100 on the same platform. 

Unfortunately this leaves us in a bit of a confused state; the KT133A offers a lot of the performance of the AMD 760 chipset, when equipped with no more than PC133 SDRAM yet we just proved that the reason for the competitive performance wasn't because of the added FSB bandwidth.  In order to investigate this issue we threw another tool into the benchmark suite to help us get a handle on exactly what was going on.