karl@ddsw1.UUCP (Karl Denninger) (02/11/88)
In article <995@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes: > >I've yet to get a chance to try the additional features of the 4.0 >firmware. Most interesting is the additon of a low speed reverse >channel that is supposed to get rid of the need to ping-pong the >connection when you're using the TB Plus for dial-up data entry, >packet ACKs, etc. One of the other sites in the area is supposed >to be getting a 4.0 version soon (I hope). So that's what they added! Well, now I understand why there is nearly no delay in what I would expect to be the 'turn around' when I'm using it interactively.... and it also explains why this nicety doesn't work when I call a Rev 3 Telebit. >Today's SYSLOG entries at my machine, impulse, show that it was >getting about 900 - 950 char/sec on messages between 2000 and 4000 >char. I didn't have any long traffic today. That is quite a bit >better than previous figures. I plan to investigate the Plus more >rigorously next week. We're hitting 950 cps some uucp transactions going to another Trailblazer/host at 9600. Occasionally we even get >11kbaud, but this is on very short messages (which fit into the buffer of the modem). Our local connection to the modem is at 19.2K Unfortunately, we don't have anyone to talk to at 19.2k yet (on both ends); I'd like to see what kind of throughput is achievable in this case... >I'm planning to pit the Plus against a Microcom 9624AX, US >Robotics, and Racal. Of the four modems above, the construction >quality is best in the Plus. The Microcom is second, with the USR >a close third. The Racal has quite a few fix-up jumpers inside. >Of the four, the Plus is the only modem not using the Rockwell >chipset for 0-2400 baud; Telebit uses an AMD "Worldchip". I would be quite interested in the results of this (I have a feeling the USR HST will be disappointing, though) ----- Karl Denninger | Data: +1 312 566-8912 Macro Computer Solutions, Inc. | Voice: +1 312 566-8910 ...ihnp4!ddsw1!karl | "Quality solutions for work or play"
larry@tapa.UUCP (Larry Pajakowski) (02/12/88)
>>Of the four, the Plus is the only modem not using the Rockwell >>chipset for 0-2400 baud; Telebit uses an AMD "Worldchip". The Worldchip only handles lower speed stuff. Max full duplex is 300bps and it will do V.21 or 202 at 1200cps with a 75bps back channel. The real techonology in the Trailbalzer is the digital signal processor chip 32010.
jeff@tc.fluke.COM (Jeff Stearns) (02/13/88)
In article <718@ddsw1.UUCP> karl@ddsw1.UUCP (Karl Denninger) writes: > ... >Unfortunately, we don't have anyone to talk to at 19.2k yet (on both ends); >I'd like to see what kind of throughput is achievable in this case... I'd be happy to participate in such an experiment. Our two Trailblazers are both locked to 19200 baud, and the Systech serial interface behind them is fast enough to send and absorb a full window's worth of data at that rate without dropping any. (A Sun model 100U runs it all (a gasp of horror is heard from the back of the room!) and can barely keep up at 19.2 if nothing else is going on.) If anybody's interested, phone or drop a note. -- Jeff Stearns Domain: jeff@tc.fluke.COM Voice: +1 206 356 5064 UUCP: {uw-beaver,decvax!microsof,ucbvax!lbl-csam,allegra,sun}!fluke!jeff Snail: John Fluke Mfg. Co. / P.O. Box C9090 / Everett WA 98206
wtm@neoucom.UUCP (Bill Mayhew) (02/14/88)
Apologies if I gave the impression that the Worldchip did the highspeed magic in the TB modem. I only mentioned it for comparison against the Rockwell off-the-shelf chips in the other modems. The serious high speed FAST mode of the TB uses a Trellis coding method, and is modulated/demoduated using an MC68000 CPU and a General Instruments DSP chip which implement a Vitterbi (sp?) algorithm. The newer TB Plus models have integrated much of the SSI / MSI functions into a Toshiba-made gate array. Another nice feature of the Plus model is that it includes a programming resistor that allows one to set the transmitter level for use in leased-line applications. --Bill
phil@amdcad.AMD.COM (Phil Ngai) (02/16/88)
In article <1009@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes: >The serious high speed FAST mode of the TB uses a Trellis coding >method, and is modulated/demoduated using an MC68000 CPU and a >General Instruments DSP chip which implement a Vitterbi (sp?) Could you explain why you call it a Trellis coding method? I think I know what Trellis coding is and I think I know what PEP is. I didn't know that PEP used Trellis, or am I misunderstanding you? -- I speak for myself, not the company. Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or phil@amd.com
wtm@neoucom.UUCP (Bill Mayhew) (02/27/88)
>Trailblazer...uses Trellis coding.
Several people have been kind enough to explain that the multiple
carrier PEP transmission mode of the Trailblazer should not be
equated to Trellis modulation used in v.29 modems. Sorry if my
incorrect statment caused any confusion.
Apparently a major benefit (which I did correctly state) of the
Trailblzer's FAST mode is that fallback can be in quite small
baudrate increments, unlike v.29 modems that have to fall back by
factors of 2.
--Billmw3s+@andrew.cmu.edu (Martin Weiss) (03/03/88)
wtm@neoucom.UUCP (Bill Mayhew) writes: >Several people have been kind enough to explain that the multiple >carrier PEP transmission mode of the Trailblazer should not be >equated to Trellis modulation used in v.29 modems. The CCITT V.29 recommendation does not include Trellis coding; only the CCITT V.32 recommendation does.