rgb@PHY.DUKE.EDU ("Robert G. Brown") (06/16/90)
That is exactly the sort of thing that I expected; I just don't have the data on the R3000. I sort of hope that the SG tech people give us some hard information. I also want to know what kind of cache it is; it could be separate data and instruction caches or they could be combined into one. I need to know how big it is (although I could do something like you have done and find out). The larger reduction in throughput (percentagewise) is probably due to the R3000 being a faster processor in the first place; given that the memory bandwidth is roughly the same in the 4D25 and the 220S, if it is the rate limiting feature then one will see a bigger fraction of performance go down the tubes on a faster processor. This just goes to show the general unreliability of benchmarks as a true measure of system performance. As I tell my users, the only way to know how a system will perform on a particular problem is to try it. Even Linpack doesn't really tell you much about cache degradation, etc. rgb