pjh@mccc.uucp (Pete Holsberg) (10/05/89)
I saw an Imprimis ad recently that hawked their WREN line of hard disks. They
listed interfaces as ST506, AT, ESDI, and SCSI. I'm familiar with ST506, ESDI
and SCSI, but what do they mean by AT? I thought that a HD with an ST506
interface could be used with an ST506 controller on an XT or AT or even an
AT&T 3B2/400. How does an AT interface HD differ from an ST506 device?
Thanks.
Pete
--
Pete Holsberg UUCP: {...!rutgers!}princeton!mccc!pjh
Mercer College CompuServe: 70240,334
1200 Old Trenton Road GEnie: PJHOLSBERG
Trenton, NJ 08690 Voice: 1-609-586-4800davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) (10/10/89)
In article <1989Oct4.234853.20690@mccc.uucp>, pjh@mccc.uucp (Pete Holsberg) writes: | I saw an Imprimis ad recently that hawked their WREN line of hard disks. They | listed interfaces as ST506, AT, ESDI, and SCSI. I'm familiar with ST506, ESDI | and SCSI, but what do they mean by AT? I thought that a HD with an ST506 | interface could be used with an ST506 controller on an XT or AT or even an | AT&T 3B2/400. How does an AT interface HD differ from an ST506 device? An AT does not have an ST506 interface, it has an ST412 (often called AT) interface. The diference is that the 412 offers "buffered seek." On the 506, to step 20 tracks the controller does a "step...wait" 20 times, while on the 412 the controller sends 20 step commands then a wait. The next effect is that the seek is faster since the head doesn't stop at each track. An AT drive will work on an ST506 controller, since it's a superset. The other way round may result in seek errors. This info taken from a Seagate tech note supplied by IBM when the first AT's came out. -- bill davidsen (davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen) "The world is filled with fools. They blindly follow their so-called 'reason' in the face of the church and common sense. Any fool can see that the world is flat!" - anon
neese@adaptex.UUCP (10/11/89)
Actually, the usage of the term AT, means the drive has a builtin
controller, like a SCSI drive has, but this controller is a ST-506
interface. It is the controller bulit in to the drive also known as IDE.
All that is needed for this type of drive is a paddle board that does the
I/O decoding. The drives are about the same price as thier MFM counterpart
but usually come RLL encoded and 1:1, so the price/performance ratio
is much better than the standard ST-506/MFM drive/controller option.
Also consider, that quite a few CPU manufacturers are building the
I/O decode port inot the motherboard, thereby not requiring the paddle
board. Which all means, you save the price of the controller and a
slot and get much better performance to boot!
Roy Neese
Adaptec Central Field Applications Engineer
UUCP @ {texbell,attctc}!cpe!adaptex!neese
merch!adaptex!neesekeithe@tekgvs.LABS.TEK.COM (Keith Ericson) (10/11/89)
In article <1989Oct4.234853.20690@mccc.uucp> pjh@mccc.UUCP (Pete Holsberg) writes: >I saw an Imprimis ad recently that hawked their WREN line of hard disks. They >listed interfaces as ST506, AT, ESDI, and SCSI. I'm familiar with ST506, ESDI >and SCSI, but what do they mean by AT? I thought that a HD with an ST506 >interface could be used with an ST506 controller on an XT or AT or even an >AT&T 3B2/400. How does an AT interface HD differ from an ST506 device? Recently some drive manufacturers have realized that a large percentage of their drives are going into a very well defined market place - the IBM AT/Clone. (Note: I didn't say the BUS is well defined!) Anyway, what they've done is to essentially put what used to be the ST506 interface (or 412 - whatever it was/is) ON THE DRIVE and eliminate the need for "all that stuff" on an interface card. The connection has been reduced to just a few, if any, IC's, to buffer the signals and maybe protect one side from a fault on the other. At least, that's what I saw in some literature the Almac salesman brought over recently. I wasn't really interested so I didn't question how multiple drives are handled, floppy/hard disk controlling, etc, etc. kEITHe