Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!overload!dillon From: dillon@overload.Berkeley.CA.US (Matthew Dillon) Newsgroups: comp.sys.amiga.programmer Subject: Re: MS-DOS emulator for CDTV? Message-ID: Date: 30 May 91 21:54:15 GMT References: <1239@cbmger.UUCP> <1991May24.021015.27939@news.iastate.edu> <7!Z_4N|@warwick.ac.uk> <1991May29.231913.25175@news.iastate.edu> <22032@cbmvax.commodore.com> Organization: Not an Organization Lines: 50 In article <22032@cbmvax.commodore.com> drysdale@cbmvax.commodore.com (Scott Drysdale) writes: >In article <1991May29.231913.25175@news.iastate.edu> taab5@isuvax.iastate.edu writes: >>In article <7!Z_4N|@warwick.ac.uk>, phupp@warwick.ac.uk (S Millington) writes: >>>In article <1991May24.021015.27939@news.iastate.edu> xgr39@isuvax.iastate.edu writes: >>>... > >> Internal modems and >>multi-serial port cards for IBM are less than 1/5 the cost of similar >>cards for Amiga, and it would be nice to be able to use these >>cards with Amiga software. > >.. > >again, there are only a few add-on serial cards for the amiga. commodore's >A2232 (7 port intelligent serial card, $400 list), ASDG's DSB (2 port "dumb" >serial card, $249 list) are examples. there are at least three other >manufacturers, but i don't know much about the products. let's use the >A2232 - show me an intelligent multiport serial card for the PC that lists for >under $12 per port ($249 / 7 * 1/5). "intelligent" in this context means it's >got it's own CPU to offload interrupt overhead from the host computer. The problem with the IBM under MSDOS is that there is NO SUPPORT FOR MORE THAN 2 SERIAL PORTS. That's right, 2, not 4. The reason is that the original serial specification hardwired IRQ 3 and IRQ 4 as well as hardwired the IO port locations and specific IO chip required, meaning that beyong a few simple hacks and a few chips that 'emulate' the originals but add fifo's, the only other solution as far as an IBM goes is to go full-custom. While you can have four serial ports you can only use 2 of them simultaniously on an MSDOS machine because THE INTERRUPTS ARE NOT SHARABLE... COM1 and COM3 are on one interrupt and COM2 and COM4 are on another, but for each interrupt only *ONE* of the serial ports may be active. What's the use of having a multi-port serial board for an IBM if you can't even use all the ports simultaniously? Thank you, I'll pass. I much prefer the Amiga and the A2232, where I can run all 7 ports simultaniously from different programs without them interfering with each other or even slowing the computer down all that much. -Matt -- Matthew Dillon dillon@Overload.Berkeley.CA.US 891 Regal Rd. uunet.uu.net!overload!dillon Berkeley, Ca. 94708 USA