Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!elroy.jpl.nasa.gov!usc!rutgers!faatcrl!jprad From: jprad@faatcrl.UUCP (Jack Radigan) Newsgroups: comp.sys.amiga.datacomm Subject: Re: 19200 baud amiga Message-ID: <1022@faatcrl.UUCP> Date: 22 Feb 91 21:46:05 GMT References: <2587@tmiuv0.uucp> <978@faatcrl.UUCP> <19116@cbmvax.commodore.com> Distribution: comp Organization: FAA Technical Center, Atlantic City NJ Lines: 48 daveh@cbmvax.commodore.com (Dave Haynie) writes: >In article <978@faatcrl.UUCP> jprad@faatcrl.UUCP (Jack Radigan) writes: >>rick@tmiuv0.uucp writes: >The real problem with high speed serial input is buffering. For every >character that comes in, you need to interrupt the CPU and have it stuff >that character somewhere. True. Is there any consideration of a FIDO, or at least one additional byte of bufering being considered for a future PAULA? From the tests I've done, that would just about do it for baseline Amigas to not have data loss problems. >On the other end of things, if you're running a packet oriented protocol, >rather than single characters, you can get a reliable Amiga-Amiga connection >going in the 150KB-200KB range. But this would mean bypassing the serial.device and going straight to the serial.resource, right? What impact does this have on the rest of the system? >> - Certain types of HD controller can also lead to data loss, those that >> are hogging the bus for DMA transfers or have device drivers that run >> at excessively high priorities are the worst offenders. >In general, the DMA devices won't be a problem. Even on the A2000/A2091, a >typical SCSI device is going to run at about 1/2 the speed of the bus, so >DMA transfes wind up in rather small packets. Nope, check that. Certain Supra DMA controllers completely stomp all over ZMODEM downloads @ 19.2kbps if the transfer is done to disk. Little to no effect for transfers to ram: though. While I may have been mistaken as to the cause of the problem, there *is* a definate interference with certain controllers and serial input. Of course, 3/4 bitplanes and/or the lack of real fast ram can also aggrevate this condition too. >> As for the A3000, I've been able to drive it at 38.4kbps without a burp. >You get a big pile of advantages in the A3000 -- faster CPU, faster memory, >and especially the hard disk, which typically takes 4%-8% of your CPU time >for transfers, rather than as much as 50% on A2000 based DMA devices. No lie! ;-) -jack-