Path: utzoo!dptcdc!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!cbmvax!fred From: fred@cbmvax.UUCP (Fred Bowen) Newsgroups: comp.sys.cbm Subject: Re: Commodore 9600 baud terminal program NEEDED! Message-ID: <6610@cbmvax.UUCP> Date: 18 Apr 89 14:13:12 GMT References: <3924@ucdavis.ucdavis.edu> <866@a.lanl.gov> <486@jolnet.ORPK.IL.US> Reply-To: fred@cbmvax.UUCP (Fred Bowen) Distribution: usa Organization: Commodore Technology, West Chester, PA Lines: 41 In article <486@jolnet.ORPK.IL.US> brendan@jolnet.ORPK.IL.US writes: >In article <866@a.lanl.gov> sct@a.lanl.gov (Stephen Tenbrink) writes: >> If you need this for a C64 you may be dissapointed. The C64 can >>barely keep up with 2400 baud emulators written in assembly language. I'm >>not sure about the C128. > > This has been the assumed standard because of the incredibly bad Kernel >RS232 routines in it..but Chris Smeets (in a telecomm conference on GEnie) >said he had some source written by someone he knew that would let the 64 >crank at up to 4800 baud (because of a total re-writing of the rs232 >handling)...I have yet to see this source, but I'm convinced that such a >thing is possible, with the right code. 'Fraid I cannot let this pass without pointing out one small detail. While I, like anyone one else, would likely implement the Kernel's RS232 handler differently, it could be argued that it was written that way to allow BASIC some time to execute. It was also written to emulate a 6551 at a time when 300 baud modems were the rage. Custom drivers which don't have to run along with BASIC, don't need to emulate a 6551, and don't have to fit in a limited ROM space can use the time for faster I/O. The processor has only so many cycles- you can spend 'em banging bits, doing expansive terminal emulation, whatever (like running a BASIC interpreter:-), but these are tradeoffs- you don't get faster data rates without giving up something. Sure the C64 can do higher nominal data rates- but what is the actual data rate? I'd bet it's still pretty darn close to 12/2400. And what was given up to make this possible? I think that the higher data rates would score big, though, with data transfer protocols, where the communication is mostly one way, the packet size is limited and usually known in advance, there is a small set of "commands" which appear in expected places, and most if not all features of the "terminal" (such as screen display and even keyscan) are suspended until the transfer is finished. -- -- Fred Bowen uucp: {uunet|rutgers|pyramid}!cbmvax!fred arpa: cbmvax!fred@uunet.uu.net tele: 215 431-9100 Commodore Electronics, Ltd., 1200 Wilson Drive, West Chester, PA, 19380