In a previous item on slow network speed with some PCI-based Macs with PCI cards installed, we quoted YARC Systems as claiming that the cause of the problem was apparently the rev. 2.8f2 boot-ROM. They have now modified this position: "Through Apple's assistance, it has been established that the cause for the Slow Network Problem is not the 2.8f2 itself. The observation that the error only occurs on machines with the 2.8f2 ROM is still valid though." Additionally, they note that not all machines with the f2 ROM revision will necessarily show the problem.
They have also revised the utility that can be used to check if you have this ROM revision or not. The ReadMe file with the utility gives further details. (Thanks, John Love.)