Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucla-cs!wales@valeria.cs.ucla.edu From: wales@valeria.cs.ucla.edu (Rich Wales) Newsgroups: comp.sys.ibm.pc.hardware Subject: Perstor controllers -- info from the horse's mouth Message-ID: <38331@shemp.CS.UCLA.EDU> Date: 24 Aug 90 19:02:17 GMT Sender: news@CS.UCLA.EDU Organization: UCLA CS Department, Los Angeles Lines: 54 I called Perstor a few days ago and had them send me one of their brochures. I called them again today and just finished speaking with one of their sales staff. Here's what I found out. I asked how it was that Perstor could get reliable performance at such high data densities, even on non-RLL drives. Their answer is that their ADRT technique encodes the data more compactly, but still uses the same flux density as MFM. The disk is =not= stressed beyond MFM specs; their method works even on drives that won't take RLL at all. ADRT is =not= a "compression" technique, so it should work no matter what a given sector contains. I was, unfortunately, unable to get any more details on the ADRT method (it's proprietary) -- but their sales brochure says it's based on the "IBM 3370 DK" technique. Perstor currently sells four different controllers: (1) PS180-16FN, for a 16-bit bus. In addition to being able to handle two hard drives, this Perstor controller (and =only= this model) can also handle two floppy drives (5.25" and/or 3.5"). (2) PS180-8XT, for an 8-bit bus. (3) PS180-8AT, for an 8-bit bus. The only difference between the -8AT and the -8XT is in the BIOS chip. I think (but am not 100% sure) that the -8AT will only work in a 286 or 386 system. (4) ADRC-9008, for an 8-bit bus. This board gets 32 sectors per track (instead of 31), but its transfer rate is 20-25% slower than the PS180-8XT. Also, the low-level format program for this board is in the BIOS (the other models come with separate formatting software). The material I got in the mail also included a long list of drives that Perstor says its controllers will work with. Some drives the salesman I spoke with said will =not= work with a Perstor include Quantum, Tandon, most Priams, older Fujitsus, and older Shugarts. Kalok drives, I was told, are "hit-and-miss"; some models work, some don't. If you connect two drives to a Perstor controller, their geometries need to be "compatible" (though not necessarily identical). "Compatible" in this context means that the two drives' sizes need to be in the same "drive table". I specifically asked about the combination of 9x1024 (e.g., a Seagate ST4096) and 4x615 (e.g., a Seagate ST225 or Lapine Titan 20), and was told these two geometries =are= compatible. Jerry Pournelle favorably reviewed the Perstor PS180-16FN in his column in the March 1990 issue of BYTE (p. 65). Disclaimer: I do not work for Perstor. In fact, I'm not even a Perstor customer yet -- though I suspect I will probably become one soon. -- -- 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."