Socket-A Chipset Comparison - April 2001

Memory Bandwidth - Cachemem

The picture we're seeing here is one that we have seen from the past two memory bandwidth tests.  The interesting thing here is that we can separate memory read performance from write performance and it helps give us a better understanding of what these various memory specifications actually give us in the end. 

Do take notice of the fact that the 2.1GB/s of memory bandwidth provided by PC2100 DDR SDRAM translates into 1GB/s of bandwidth in this synthetic benchmark, and as we've seen in the previous tests, you can't expect much more than this in real-world situations.

Another thing to take note of is the fact that when the MAGiK1 chipset is used with the 100MHz DDR FSB the memory read performance figures drop significantly.  They drop so far in fact that the PC1600 DDR solution is actually offering lower memory read performance than the same chipset with PC133 SDRAM.  We'll get back to the explanation behind this in a bit, for now let's have a look at the write performance picture.

Notice something different?  That's right, the write performance is considerably lower for most of the chipsets than their memory read performance.  The explanation is simple; when writing data is actually being changed, however when reading it is nothing more than a process of getting data from one place to another.  In the case of read performance you are often limited by things like bus speeds, bandwidth and latency, but in the case of write performance other limitations come into play that keep the performance much lower. 

The AMD 760 chipset actually seems to do quite well here, offering a significant increase in memory write performance than any of the other solutions here.  Even the ALi DDR solution is unable to offer any significant bandwidth advantage over the PC133 contenders.  The only thing that comes to mind here is AMD's SuperBypass feature which came in handy with the AMD 750 chipset and would presumably be present in the 760 as well.  Whether it is the cause for the incredible write performance advantage of the AMD 760 or not is another question that we will continue to investigate.