By just looking at memory bandwidth it is hard to judge the performance of any platform, other factors come into play when you look at the overall performance. To be able to determine if PC-1066 and PC-1200 also make a significant impact on performance under real-world conditions we've used SYSmark 2001 to compare the various speed grades of RDRAM.
Fig 7. The SYSmark 2001 benchmark results paint a very clear picture, PC-1066 and PC-1200 RDRAM offer a substantial increase in performance over PC-800.
It needs no further explanation that PC-1066 and PC-1200 offer a substantial increase in performance over PC-800. If we look at the SYSmark 2001 results once more in terms of % increase, or decrease, in performance, where PC-800 is considered 100%, we find the following:
Pentium 4 1.5Hz, i850 chipset
SYSmark 2001: (PC-1066/PC-800) = (178/161) » 10.5%
SYSmark 2001: (PC-1200/PC-800) = (188/161) » 16.8%
Pentium 4 2.0Hz, i850 chipset
SYSmark 2001: (PC-1066/PC-800) = (202/184) » 9.7%
SYSmark 2001: (PC-1200/PC-800) = (216/184) » 17,4%
The SYSmark 2001 benchmark clearly shows that the gap between PC-800 and PC-1066 is where the most performance is gained. Going from PC-1066 to PC-1200 and a 150MHz FSB doesn’t scale similar to going from PC-800 to PC-1066. This is most obvious with the 1.5GHz Pentium 4, in that respect the 2.0GHz performs better, albeit only slightly.
If this trend continues, and it looks like it will, higher clockspeed Pentium 4s will benefit more from a larger memory bandwidth than lower clocked Pentium 4s. Therefore it will be interesting to see what the i845-D will be capable of when teamed up with a +2.5GHz Pentium 4 and PC2100 DDR SDRAM, it could very well be starving for bandwidth and not perform as expected, much like the i845 with SDRAM.