From owner-freebsd-hackers Sun Oct 8 09:41:45 1995 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.6.12/8.6.6) id JAA06820 for hackers-outgoing; Sun, 8 Oct 1995 09:41:45 -0700 Received: from etinc.com (etinc-gw.new-york.net [165.254.13.209]) by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id JAA06815 for ; Sun, 8 Oct 1995 09:41:42 -0700 Received: from et.htp.com (et.htp.com [199.171.4.228]) by etinc.com (8.6.11/8.6.9) with SMTP id MAA26550; Sun, 8 Oct 1995 12:49:20 -0400 Date: Sun, 8 Oct 1995 12:49:20 -0400 Message-Id: <199510081649.MAA26550@etinc.com> X-Sender: dennis@etinc.com X-Mailer: Windows Eudora Version 2.0.3 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: Warner Losh From: dennis@etinc.com (dennis) Subject: Re: VLB Disk Controllers Cc: hackers@freebsd.org Sender: owner-hackers@freebsd.org Precedence: bulk >: I have had problems with vlb cards running above 33 MHZ. The effect appears >: like the loss of interrupts or extreme interrupt latency. I have seen this >: especially bad on amd 486dx2/80 (vlb clk 40mhz) and 486dx2/100 (vlb clk 50mhz). >: I suspect the problem would exist on 486dx50 as well. > >The VLB spec doesn't go above 33MHz for two or more cards. It goes, >I'm told, to 50MHz for one card, but I've also heard that the 33MHz >limit is hard, so I don't know what to believe. Either way, it isn't >surprizing that you've had problems with one i na 40MHz or 50MHz >system, since you'll likely have a video card on that bus as well. > >I've had no problems with my VLB UltraStor 34F and either a no name >ET4000 card, or an S3 #9 Lvl 11 at 33MHz. > It all depends on the MB, and even the tuning parameters are somewhat bogus on some boards. Some MBs insert cycles so that any speed with work, but they're not as fast. What you want is one where you can tune it precisely. Most cards are designed to work at 40mhz at least, but thats based on assumptions that may not hold true. Dennis