Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-winken!uunet!philmtl!ray From: ray@philmtl.philips.ca (Raymond Dunn) Newsgroups: comp.sys.ibm.pc Subject: Re: 1.44 meg 3 1/2" drive whoas Message-ID: <546@philmtl.philips.ca> Date: 29 May 89 22:16:56 GMT References: <634@pmafire.UUCP> <935@mks.UUCP> <8141@killer.DALLAS.TX.US> <3479@westfort.UUCP> <11389@netnews.upenn.edu> <543@philmtl.philips.ca> <11412@netnews.upenn.edu> Reply-To: ray@philmtl.UUCP (Raymond Dunn) Organization: Philips Electronics Ltd. - St. Laurent P.Q., Canada Lines: 69 In article <11389@netnews.upenn.edu> harnyo@grad2.cis.upenn.edu.UUCP (Suwandi Harnyo) writes: > [absolute drivel] In article <543@philmtl.philips.ca> I write: > [grumbles about the above drivel] In article <11412@netnews.upenn.edu> harnyo@grad2.cis.upenn.edu.UUCP (Suwandi Harnyo) continues to try to justify the drivel: >I am not sure about this. I always thought that having a 16 bits floppy >controller on my AT is definitely faster than a 8 but controller. That's >why I pay more for the 16 bit controller than the cheaper 8 bit one. >Comment ? Yes, I can see why you are not sure about it even though you always thought it. (:-( (:-( That is what was wrong with your original posting, and I'm not sorry to be given the opportunity to re-iterate this: - DO NOT POST AS FACTS, THAT WHICH YOU ARE NOT SURE ABOUT, EVEN THOUGH "YOU ALWAYS THOUGHT IT" Expressing opinion during a discussion is, of course, another matter - in that case you'd better check your facts even MORE carefully or you'll be REALLY flamed (:-) (:-). Now to respond to your request for comment. Excuse me for being rude, but it only takes 30 seconds prior to posting to verify the validity of FACTS - in the AT technical reference manual, Norton, or your own favourite bible. On an AT, the floppy disk controller is connected to channel 2 of DMA Controller 1. DMA Controller 1 is physically only capable of supporting 8-bit transfers. The system BIOS and most software which directly accesses the floppy, does so via the DMA. And finally, the speed of transfer to a floppy disk is limited by the physical rotation speed of the media, NOT the width of the data bus. A 64-bit bus wouldn't give you faster data transfer to a floppy!! This is the end of the real story. Period. Lets look at where the myth of a 16-bit floppy controller might come from: AT *hard* disk controllers are 16-bit, and many do have embedded floppy controllers. Data is transferred to the hard disks 16-bits at a time, interestingly enough *NOT* using the DMA, but by programmed I/O - it's faster than the DMA on the 286. The floppy controllers on these cards are still 8-bit devices. It *would* be possible to have a floppy controller that could be controlled by 16-bit wide programmed I/O, but it would also have to be capable of being driven in a compatible 8-bit mode. Such a controller card would have to have its own BIOS chip to replace the system BIOS which contains the compatible floppy driver code. I don't know of any standalone floppy controller cards for AT's - that doesn't of course mean that there aren't any. The functionality is nearly always provided on the hard disk controller card. Please name one 16-bit floppy controller card. -- Ray Dunn. | UUCP: ..!uunet!philmtl!ray Philips Electronics Ltd. | TEL : (514) 744-8200 Ext: 2347 600 Dr Frederik Philips Blvd | FAX : (514) 744-6455 St Laurent. Quebec. H4M 2S9 | TLX : 05-824090