Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!tut.cis.ohio-state.edu!mailrus!ames!haven!adm!smoke!gwyn From: gwyn@smoke.BRL.MIL (Doug Gwyn) Newsgroups: comp.sys.apple Subject: Re: ZMODEM/EASYLINK Message-ID: <10417@smoke.BRL.MIL> Date: 19 Jun 89 01:10:12 GMT References: <8906180052.AA20316@obsolete.UUCP> Reply-To: gwyn@brl.arpa (Doug Gwyn) Organization: Ballistic Research Lab (BRL), APG, MD. Lines: 14 In article <8906180052.AA20316@obsolete.UUCP> nazgul@obsolete.UUCP (Kee Hinckley) writes: >However it would also give Apple ][s problems because disk accesses >turn off interrupts, and you would lose characters. This isn't an inherently insoluble problem, because virtually all UARTs, ACIAs, or whatever in use today are at least double-buffered, giving the operating system one character assembly time to deal with inputting the buffered character. At 2400bps, that's 1/240 seconds, i.e. more than 4 milliseconds. If interrupts are disabled only for shorter duration than that, no received characters need be lost. I don't know how long ProDOS or GS/OS disables interrupts during I/O for the various kinds of supported disk drives, but all of them should be able to transfer a sector in less than 4 msec.