Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!wrdis01!news.cs.indiana.edu!ux1.cso.uiuc.edu!news.iastate.edu!cs352a41 From: cs352a41@cs.iastate.edu (Adam Goldberg) Newsgroups: comp.dcom.modems Subject: Re: USR Courier V.32bis questions etc.... Message-ID: Date: 21 Apr 91 15:19:34 GMT References: <6465@husc6.harvard.edu> <1991Apr21.032236.21724@netcom.COM> Sender: news@news.iastate.edu (USENET News System) Organization: Iowa State University, Ames IA Lines: 53 gandrews@netcom.COM (Greg Andrews) writes: >In article <6465@husc6.harvard.edu> conrad@popvax.harvard.edu writes: >> >>If I am right (and the article is either wrong or VERY poorly written), >>what is the highest throughput that could be hoped for? 14,400 X 4 = 57,600. >>I know that this would be difficult to sustain on real data, but is it a good >>number for a top limit? >> If these modems can theoretically reach throughputs of 57,600 bps, what >>is the highest DTE rate that they support? I should think 57,600 bps would be >>necessary. >> >Why should it be necessary if, as you say, you wouldn't be able to get that >much compression out of real data? How many computers can handle a sustained >data rate of more than 38400 bps? What kind of processor hardware would be >necessary for the modem to handle a 14400 bps (full) duplex modulation AND >compression/decompression of the data AND an RS232 interface speed of 57600? >Would you really be willing to give up the amount of money and desk space for >such a monster? Especially if you know in advance that you won't utilize the >speed capabilities beyond 38400 bps more than perhaps 2% of the time? >I think the reason most modem manufacturers are creating modems with a max >RS232 speed of 38400 are doing it for three reasons: (a) It doesn't require >exotic, costly processors, (b) Real life data transfers won't be more than >2.7:1 compressible 98% of the time, and (c) Few computers can handle data >rates above 38400 bps. In short, they're designing a modem that will meet >your data transfer needs without exceeding your budget needs. I know this is slightly off the subject, BUT: Since it is (theoretically) possible for an effective data transfer rate of 57,600, but it would take 'exotic, costly processors', it struck me: Hmmm, is it possible (or has anyone attempted) to: o Construct such a very, very fast modem. o Design it as an internal card with DMA--ie, it would take a very strange RS232 port to support such high speeds, and the processor would be completely taken over by it, so wouldn't it make sense to have the modem work like a disk drive and deposit data directly to memory? Clearly if a HST modem has a 68k inside of it... Anyone know of such a beast (that is, know of anyone ever considering building such a beast--I'm pretty sure it hasn't ever been commercially available)? Just a thought, -- +-----------------------------------------------------------------------------+ ! Adam Goldberg ! * ! "It's simple! Even a PASCAL ! ! cs352a41@cs.iastate.edu ! * ! programmer could do it!" ! +-----------------------------------------------------------------------------+