From owner-freebsd-hackers Thu Feb 20 04:38:07 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.5/8.8.5) id EAA09945 for hackers-outgoing; Thu, 20 Feb 1997 04:38:07 -0800 (PST) Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.19]) by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id EAA09937 for ; Thu, 20 Feb 1997 04:38:04 -0800 (PST) Received: (from bde@localhost) by godzilla.zeta.org.au (8.8.3/8.6.9) id XAA00491; Thu, 20 Feb 1997 23:34:43 +1100 Date: Thu, 20 Feb 1997 23:34:43 +1100 From: Bruce Evans Message-Id: <199702201234.XAA00491@godzilla.zeta.org.au> To: bde@zeta.org.au, sos@ravenock.cybercity.dk Subject: Re: Screen flickering Cc: brian@awfulhak.demon.co.uk, brian@utell.co.uk, hackers@freebsd.org Sender: owner-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk >> 1. Make the vertical retrace interrupt handler a "fast" interrupt >> handler so that it has a low latency and can't be interrupted. >> Don't use too many other "fast" interrupt handlers, or the >> interrupt latency might be too high. >> 2. Program the sparkly registers in the vertical retrace interrupt >> handler. Do this in less than 20 usec or someone will complain >> that the interrupt latency is too high. > >I'd like to do it this way, but lots of the crappy VGA cards thats >out there (and often its the same ones that produces most of >the annoing jitter) doesn't support an interrupt, and some only >allows using NMI. >However it is quite easy to implement, so..... It's not easy. Multiple interrupts per driver are unusual and not supported by config. Fast interrupt handlers are unusual and must be programmed carefully. Bruce