amanda@mermaid.intercon.com (Amanda Walker) (02/15/90)
In article <5374@okstate.UUCP>, minich@a.cs.okstate.edu (MINICH ROBERT JOHN) writes: > (If I remember correctly, average Ethernet > speeds are in the 1-10Mbps range [where LocalTalk is at .23 Mbps].) "raw" throughput for Ethernet is 10mpbs, but unless the software can take advantage of it, most of that usually goes unused. To take the canonical example, copying files via TOPS is optimized for LocalTalk, which means it doesn't try very hard to push data across any faster. Public Folder does a better job of pushing the bits across the wire--it's quite a pleasure to use over EtherTalk. Even better is using, say, FTP, which can use the congestion-control features of TCP/IP to maximize the usage of whatever media it's running over. Just to throw real live measurements in (gasp! :-)), the last time I benchmarked the FTP code in our product I got the following set of numbers (all measured it bytes per second): Mac II, Ethernet, going to SCSI disk: 55-60K Mac II, Ethernet, going to RAMdisk: 75-76K Mac II, LocalTalk, going to SCSI disk: 17K Mac II, LocalTalk, going to RAMdisk: 17K You can probably get another few K per second out of LocalTalk, but this gives an idea of the difference the media can make if the code can take advantage of it. It also shows that there comes a point where the network isn't all of the bottleneck any more... Caveat: our code is not really optimized for Ethernet, it just does a pretty good job. With some work and careful tuning, you can squeeze a lot more out. MacTCP has been clocked at up to 375K bytes/second over Ethernet, according to Apple (no disk access). This could probably be as much as doubled (on an idle Ethernet) before running into media limitations. On the other hand, the EtherTalk software architecture isn't designed for truly high performance, since the MacOS doesn't really have real-time response capabilities. The doubling mentioned above might have to involve bypassing the .ENET driver and handling board interrupts directly, but that's seldom worth (a) the effort and (b) the loss of device independence. -- Amanda Walker InterCon Systems Corporation "Many of the truths we cling to depend greatly upon our own point of view." --Obi-Wan Kenobi in "Return of the Jedi"