tim@hoptoad.uucp (Tim Maroney) (11/11/88)
In article <549@uvicctr.UUCP> mlevy@uvicctr.UUCP (Michael Levy) writes: >I saw an ad. in MacWorld for "FlashTalk" >which is a box from TOPS that will speed up appletalk >(localtalk) by "up to 3 times". Has anyone tried this? Anyone >know how it works? Sure, the principle is easy. It runs the same protocols as the normal LocalTalk protocols on the same kind of wire, but at a higher clock rate. Just about three times higher, in fact. FlashTalk can coexist with LocalTalk on the same wire; the FlashTalk LAP is set up to avoid stepping on any LocalTalk-speed packets, and though LocalTalk packets may step on FlashTalk packets, the higher-level protocol will resend. A look-alike LAP driver on the Mac automatically reroutes Appletalk applications through the FlashTalk box. Also, every IBM PC Appletalk board from TOPS already has FlashTalk built in. Now the bad news. Three times the clock speed does not mean three times the user-visible performance. Most throughput constraints on protocol performance are per-packet rather than per-byte. Furthermore, contention problems might well be expected to cause some serious degradation in real networks. When Kinetics came out with their Ethernet cards a while back, it turned out that TOPS only ran about three times as fast, despite a raw performance improvement of thirty times between Ethernet and Localtalk; I'm not sure what the exact figures are for FlashTalk TOPS, but I'd be surprised if you could get more than two times real performance multiplier under optimal conditions. The three time multiplier is advertising hype. Wait, it gets worse. I've found that more than 50% of the things I've used Appletalk for have been internetwork applications of some kind or another. That is, two networks are hooked together by bridge or gateway. There aren't any bridges or gateways that work at the FlashTalk speeds available. That means even the 2x or less speedup you get from FlashTalk only applies from the same network to the same network. If you're doing a TOPS transfer with someone from another department, it probably goes through a Hayes Interbridge, which forces the transfer to run at the old speed. If you're doing something on TCP/IP, it's probably through a Kinetics Fastpath to an Ethernet, and again, the Fastpath only speaks Appletalk at present. Don't hold your breath waiting for upgrades to your existing hardware, either, though faster bridges and gateways will probably be available in 1989. My feeling is that few single-network setups are really easier to use than paper-message-and-floppy-passing traditional approaches; if you don't have at least two LT networks and a lot of transfer between them, your need for a LAN is questionable. But if you do, you'll find FlashTalk helps for half or less of your applications, and that it helps far less than TOPS would like you to think. Oh, one more thing. After the initial leak on FlashTalk, the "MacInTouch" bozos at MacWeak had all sorts of really intelligent questions about it. One in particular was "Will there be a FlashTalk for the LaserWriter?" We all got a lot of laughs out of that one; why do the magazines let people write about things they know nothing about? First, you'd have to do a ROM swap, which is impossible for a third party developer; second, the LaserWriter's performance is not even slightly limited by network bandwidth -- the limits are in the PostScript interpreter and the maximum speed of the Canon engine. You could pump in PostScript three times as fast and all it would do is slow down the printer slightly by increasing the time the LaserWriter's 68000 spends processing interrupts.... More technical details on request. Not much of it falls under non-disclosure. Disclaimer: I don't work for TOPS. I used to. The management is dishonest and exploitative and I left, drastically increasing my income and mental health in the process. Don't work there if you respect yourself. -- Tim Maroney, Consultant, Eclectic Software, sun!hoptoad!tim "The Diabolonian position is new to the London playgoer of today, but not to lovers of serious literature. From Prometheus to the Wagnerian Siegfried, some enemy of the gods, unterrified champion of those oppressed by them, has always towered among the heroes of the loftiest poetry." - Shaw, "On Diabolonian Ethics"