Path: utzoo!attcan!uunet!ogicse!mintaka!bloom-beacon!vaxeline!gordon From: gordon@vaxeline.COM (*Hobbit*) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: Conflicting Cards. Help Needed. Message-ID: <1207@vaxeline.COM> Date: 29 Oct 90 19:02:54 GMT References: Reply-To: gordon@vaxeline.ftp.com (Gordon Lee) Organization: FTP Software, Inc. Lines: 50 In article mat@zeus.opt-sci.arizona.edu (Mat Watson) writes: >With either the modem >or the serial I/O card installed by itself each of the cards >works fine. Howerver, if both are installed at the same time >neither of them works correctly. This included the system >failing to recognize one of the cards altogether even after >we had checked to make *sure* that each of the cards had a >unique COM/IRQ number pair compatible with the software on >my system. > >Any help will be appreciated. You never make any mention of I/O addresses. You must verify that the cards do not conflict in I/O address space. port interrupt I/O address space COM1 IRQ4 3F8-3FF COM2 IRQ3 2F8-2FF There should be jumpers on the boards which allow you to set the I/O address. To find out which address a board is trying to use, boot your PC with only one board installed and use DEBUG to examine address 0040:0000. There you will find the swapped value of the I/O addr of the serial port: C:\> debug -d 40:0 0040:0000 F8 03 00 00 00 00 00 00-BC 03 78 03 00 00 00 00 -q C:\> You will know that your system is configured correctly when the values at location 0040:0000 look something like this: -d 40:0 0040:0000 F8 03 F8 02 00 00 00 00-BC 03 78 03 00 00 00 00 My guess is that the two boards are both configured to use 3F8 and the BIOS routines in the POST cannot see both boards. Subsequent operations performed on the I/O address will induce colliding responses from the boards with unpredicatable results. See the IBM Tech Ref section on I/O controllers for more info. Hope this helps -- ========================================================================== Gordon Lee Member, Technical Staff FTP Software, Inc. (617) 246-0900 x287