Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!decwrl!elroy.jpl.nasa.gov!ucla-cs!wales@valeria.cs.ucla.edu From: wales@valeria.cs.ucla.edu (Rich Wales) Newsgroups: comp.sys.ibm.pc.hardware Subject: OMTI HD controller and strange interleave inconsistency Message-ID: <38667@shemp.CS.UCLA.EDU> Date: 6 Sep 90 17:26:05 GMT Sender: news@CS.UCLA.EDU Organization: UCLA CS Department, Los Angeles Lines: 72 I have been experiencing a strange problem with the interleave effi- ciency of various disks and controller cards on my system. My computer is a "baby-AT" -- an 8-MHz 286 motherboard with an 8-bit, 4.77-MHz XT-compatible I/O bus. Up until recently, I was using two 32-meg RLL drives (one by Lapine, one by Kalok). These two drives were originally packaged as hard-drive-card assemblies -- one (4 years old) with an SMS/OMTI 5527 controller, the other (one year old) with a Western Digital WD1004-27X controller. I rearranged things so that both drives were running off of a single controller. With the OMTI controller, I was able to use an interleave of 4:1 on the drives. With the WD, on the other hand, the best I could get away with was a 6:1 interleave. (When I say I was "able" to use such-and-so interleave, of course, what I mean is that this was the best interleave that still gave decent per- formance. I have no problem telling the WD to do a low-level format at 4:1 or 5:1 -- but the resulting throughput is atrocious.) This would have been fine -- except that, a few days ago, I got a new drive (a 65-meg Seagate ST277R-1). I intended to install this drive in place of one of my old 32-meg drives. However, to my chagrin I discov- ered that the OMTI controller doesn't have dynamic configuration capa- bilities and insisted on formatting the new drive with 32-meg parameters (615 cylinders, 4 heads). The WD controller does have dynamic configu- ration, of course -- but, as I said, it could only do a 6:1 interleave. There is a bank of several jumpers on the OMTI card. Perhaps some of them select the drive geometry. But there's no way to tell. The hard drive card manual didn't say what the jumpers do.) I tried calling the company which originally made the hard drive card containing the OMTI controller, to see if they had any ideas. Unfortu- nately, they said Scientific Micro Systems (the people who made the OMTI controller in question) had been bought out by some other company -- they didn't know who -- and that they didn't use OMTI controllers in their products any more anyway. So, I'm left with a 4-year-old controller that gets great performance but doesn't know about 65-meg drives -- and a new controller that can talk to just about any disk, but requires a high interleave and gets significantly lower throughput. I bought a brand-new Western Digital WD1004-27X yesterday, just in case there might be some revision level improvement in the past year. No luck; the new WD controller can also do only 6:1 in my system. Everyone I've described this to (including people at both Western Digi- tal and Seagate) thinks I'm crazy. The interleave, they say, is a function of the computer system, not the controller. If one RLL con- troller can do 4:1 in a given computer, then any RLL controller should be able to do the same. To even =ask= whether a given controller is fast enough to achieve a given interleave is to display a fundamental misunderstanding of the problem. The only thing I can think of is that perhaps my OMTI controller isn't "really" doing true RLL. A disk formatted using the OMTI won't work on the WD (or vice versa) without being reformatted. Is it possible that a 4-year-old "RLL" controller might not be the same thing as a modern "RLL" controller? Any ideas or comments? Does anyone know who bought out SMS or OMTI? Maybe =they= can explain this. -- -- Rich Wales // UCLA Computer Science Department 3531 Boelter Hall // Los Angeles, CA 90024-1596 // +1 (213) 825-5683 "You must not drink the tea. It is deadly to humans."