toddpw@tybalt.caltech.edu (Todd P. Whitesel) (03/01/90)
jeffd@csd4.csd.uwm.edu (Jeffrey Alan Ding) writes: > At 9600 baud, the computer chokes. I send >it an AT command and I don't even get the OK signal back. I tried >several term programs including Kermit, Talk is Cheap, Zlink, and Mousetalk. >Talk is Cheap was the fastest in scrolling. No program worked at 9600 baud. >My computer is only running at 1 MHz. So was my ][+ when it ran 9600 for months without missing a character. I wrote my own term program and interrupt routines, but any good terminal program should handle 9600. Kermit on my ][+ runs at 19200 without losing characters either. Chances are it is the interrupt overhead of the //c firmware and ProDOS. ProDOS has horrendous interrupt overhead (worst case 400 microseconds) because it has to save all the memory state softswitches and provide a 'standard memory state' to the interrupt handler. (My term program ran under DOS and in much less than 48K so I just hooked directly into the interrupt vector. Total interrupt processing time was about 100 microseconds or 10% of the CPU at full speed 9600 baud reception. Worked like a charm.) Still, you should be able to handle 9600 baud because even at full rate reception over half of the //c's CPU time is left over -unless- your term program sucks and it's interrupt handler takes forever, which I really doubt. It's probably the //c's firmware. Todd Whitesel toddpw @ tybalt.caltech.edu
nagendra@bucsf.bu.edu (nagendra mishr) (03/02/90)
one other reason why modems mess up is if you have too many phones connected to the same outlet. try and unplugging everything but the modem from the telephone jacks, and it might not loose characters. nagendra@bucsf.bu.edu
pnakada@oracle.com (Paul Nakada) (03/02/90)
In article <1990Mar1.103507.13022@spectre.ccsf.caltech.edu> toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes: jeffd@csd4.csd.uwm.edu (Jeffrey Alan Ding) writes: > At 9600 baud, the computer chokes. I send >it an AT command and I don't even get the OK signal back. I tried >several term programs including Kermit, Talk is Cheap, Zlink, and Mousetalk. >Talk is Cheap was the fastest in scrolling. No program worked at 9600 baud. >My computer is only running at 1 MHz. [ stuff deleted ] Still, you should be able to handle 9600 baud because even at full rate reception over half of the //c's CPU time is left over -unless- your term program sucks and it's interrupt handler takes forever, which I really doubt. It's probably the //c's firmware. Todd Whitesel toddpw @ tybalt.caltech.edu I had the same problem... I have a feeling that the //c interrupt firmware is too slow for 9600 bps.. I had the exact same problems with a 9600 bps MNP 6 modem. The problem went away when I got a 8 Mhz Zip Chip, even at 19.2K bps.. All of this was true with proterm, zlink, and kermit. -Paul pnakada@oracle.com nakada@husc4.harvard.edu