From owner-freebsd-hardware Fri Jul 19 13:42:59 1996 Return-Path: owner-hardware Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id NAA18068 for hardware-outgoing; Fri, 19 Jul 1996 13:42:59 -0700 (PDT) Received: from lserver.infoworld.com (lserver.infoworld.com [192.216.48.4]) by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id NAA18062 for ; Fri, 19 Jul 1996 13:42:56 -0700 (PDT) Received: from ccgate.infoworld.com by lserver.infoworld.com with smtp (Smail3.1.29.1 #12) id m0uhOBg-000wzYC; Fri, 19 Jul 96 15:38 PDT Received: from cc:Mail by ccgate.infoworld.com id AA837808823; Fri, 19 Jul 96 14:30:00 PST Date: Fri, 19 Jul 96 14:30:00 PST From: "Brett Glass" Message-Id: <9606198378.AA837808823@ccgate.infoworld.com> To: (Rob Schofield), freebsd-hardware@freebsd.org Subject: Re: Multiple COM ports with same IRQ Sender: owner-hardware@freebsd.org X-Loop: FreeBSD.org Precedence: bulk It'd only be possible to implement shared IRQs on ISA if (a) The motherboard chipset can accept level-triggered interrupts; (b) Each peripheral board sharing the IRQ was rewired to be open-collector (many are implemented in VLSI, so you'd probably have to cut traces and add parts); (c) A pullup resistor was placed on the motherboard; and (d) All the software (including, possibly, the BIOS) was rewritten to work with the changed hardware. Whadda mess. --Brett