lane@cs.dal.ca (John Wright/Dr. Pat Lane) (04/10/90)
OK, I know I should look this up somewhere and I've been meaning to but
I haven't stumbled over it yet and I can't resist any more.
What exactly is ESDI and how is it distinguished from ST506 and SCSI?
I am aware, as the article I reference stated, that ST506, ESDI and SCSI
are competing interfacing standards for hard disk drives (and other
peripherals, I assume). I gather they are successors to the old ST412
standard that we all used to hook out ST225's to our WD1002's. I gather
ST506 is physically the same as ST412. I am vaguely aware of SCSI as a
very high speed serial interface where devices are daisy chained on a
single cable. (I even remeber the old HP GPIB interface!) But I have
no idea what ESDI is.
Could some kind soul give me a quick comparative description on ST412,
ST506, SCSI, ESDI and any other notable inteface (and correct me if I've
said anything incorrect above)?
Lately, I've been working with drives from Western Digital and Miniscribe
that have the controller built into the drive (now called an "intelligent
storage peripheral" or somesuch) and are connected to a simple "adapter"
card by a single ribbon cable which can be daisy chained to other devices.
Where do these fit into the scheme of thinks.
Thanks very much for any information and please mail me a copy even if
you post a response because I miss alot of news. Thanks, again.
--
John Wright ////////////////// Phone: 902-424-3805 or 902-424-6527
Post: c/o Dr Pat Lane, Biology Dept, Dalhousie U, Halifax N.S., CANADA B3H-4H8
Cdn/Eannet:lane@cs.dal.cdn Uucp:lane@dalcs.uucp or {uunet watmath}!dalcs!lane
Arpa:lane%dalcs.uucp@uunet.uu.net Internet:lane@cs.dal.cascjones@sdrc.UUCP (Larry Jones) (04/12/90)
In article <1990Apr10.081001.315@cs.dal.ca>, lane@cs.dal.ca (John Wright/Dr. Pat Lane) writes: > Could some kind soul give me a quick comparative description on ST412, > ST506, SCSI, ESDI and any other notable inteface (and correct me if I've > said anything incorrect above)? > > Lately, I've been working with drives from Western Digital and Miniscribe > that have the controller built into the drive (now called an "intelligent > storage peripheral" or somesuch) and are connected to a simple "adapter" > card by a single ribbon cable which can be daisy chained to other devices. > Where do these fit into the scheme of thinks. OK, here's a quick run-down. ST-412 and ST-506 are the traditional hard disk interfaces, named for the Shugart drives which implemented them. They are nearly identical and I don't remember what the exact difference is between them. The main thing to know is that the drive has very few electronics on it and very low-level analog signals are send across a (relatively) long cable to the controller which does most of the work. This makes them prone to electrical interference. If you have multiple drives, almost all of the electronics are shared, reducing your cost per drive. SCSI (Small Computer System Interface) puts the entire controller on the drive and sends only the actual data characters across the cable. Other devices with their own controllers can attach to the same cable. The cable is attached to a host adaptor which is more like a serial interface than a disk controller. If you have multiple drives, none of the electronics are shared. Since there is no standard for host adaptors and lots of different companies make different, incompatible ones, it can be very difficult to find a driver for a particular device which uses the adaptor you have -- this makes it hard to have different types of devices attached to the same cable. ESDI (Enahnced Small Disk Interface) compromises by putting all of the analog electronics on the drive, the digital electronics on the controller, and sending digital signals across the cable. This means that it is much less prone to electrical interference and thus can maintain much tighter tolerances allowing more data to be recorded on the disk reliably. Multiple drives share some of the electronics, but not all. Other devices are not supported, just disks. IDE (Integrated Drive Electronics) puts the entire controller on the drive by sending all the PC bus signals across the cable. This is kind of like SCSI but with essentially no host adaptor and no support for other devices. Like SCSI, multiple drives have completely separate electronics. ---- Larry Jones UUCP: uunet!sdrc!scjones SDRC scjones@SDRC.UU.NET 2000 Eastman Dr. BIX: ltl Milford, OH 45150-2789 AT&T: (513) 576-2070 "You know how Einstein got bad grades as a kid? Well MINE are even WORSE!" -Calvin