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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!news.mel.connect.com.au!news.mel.aone.net.au!grumpy.fl.net.au!news.webspan.net!newsfeeds.sol.net!mr.net!newshub.tc.umn.edu!fu-berlin.de!irz401!orion.sax.de!uriah.heep!news From: j@uriah.heep.sax.de (J Wunsch) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Embedded FreeBSD Date: 21 Jan 1997 01:02:09 GMT Organization: Private BSD site, Dresden Lines: 51 Message-ID: <5c14ih$7nn@uriah.heep.sax.de> References: <32B744C0.2DA9@wdc.net> <5bdbd0$uih@news.aus.world.net> <32DA62A7.A91@onramp.net> <5be62a$14b@qnx.com> <5bqs4v$oar@uriah.heep.sax.de> <5c08m3$dvk@qnx.com> Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) NNTP-Posting-Host: localhost.heep.sax.de Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Newsreader: knews 0.9.6 X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:34230 doug@qnx.com (Doug Santry) wrote: > The kernel is riddled with splhigh() calls. I wouldn't trust a device > that needs attention in under 2 microseconds on a Unix system. QNX > can guarantee it on a 200 MHz pentium. That is the worst case interrupt > latency. Sure, 2 µs is certainly out of the question with a Unix kernel. 20 µs probably not. Hey!, my old CP/M BIOS had to pick up one byte after each 16 µs from the FDC -- without DMA. :-) The biggest problem is to keep the splhigh() times short. > If you are making a product which you plan to sell by the > thousand, then you can save tons of $$$ with a small memory > footprint. I can't see a Unix being effective in 50k. Minix maybe. :) But it's right, today's Unices are simply too fat. OTOH, i think if you've finally configured a QNX that does all the filesystem and network and foobar and kitchensink stuff, it'll be a megabyte as well. The sad thing with the BSD kernel is only that it is bloated a little here, and a little there. ``Yet another constant string...'' Thus it is hard to scale down. > We don't distribute our source because our customers don't need it. That's always easy to claim. :) Well, just curious: did any of your customers ever ask you about getting the source? If so, what has been your reaction? Back in the era when i had to live with DG/UX (Data General's Unix), we sometimes also got the OS source if we needed it. Sure, most of the time, it's easier to rely on a vendor. But as soon as it gets to your own device drivers, you usually love it to at least get a (working) template. I would also have loved it to get all the source codes for those things where we have noticed bugs... > Don't get me wrong either. I love Unix. I have made contributions to the > the FreeBSD kernel. But there are areas where Unix is simply not as good > as QNX, they are real-time applications and embedded systems. Sure. I didn't claim Unix being an RT OS either. It's a ``timesharing OS'', in the classical categorization. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)