dirk@dksoft.incom.de (Dirk Koeppen) (09/30/89)
Does it work to connect a synchronous (4 MB/sec) disk drive and an asynchronous (1.5 MB/sec) streamer onto the same SCSI bus on the 386/ix Adaptec 1540 controller ? Does the driver switch the disk drive into sync. mode or does it use both devices at async mode ? thanx, dirk@incom.de
jhood@biar.UUCP (John Hood) (10/03/89)
In article <307@dksoft.incom.de> dirk@dksoft.incom.de (Dirk Koeppen) writes: >Does it work to connect a synchronous (4 MB/sec) disk drive and >an asynchronous (1.5 MB/sec) streamer onto the same SCSI bus on >the 386/ix Adaptec 1540 controller ? Does the driver switch the >disk drive into sync. mode or does it use both devices at async >mode ? According to Adaptec documentation, the controller itself handles negotiation for synchronous/asynchronous operation. This is an option selected by a jumper on the board. --jh-- John Hood, Biar Games snail: 10 Spruce Lane, Ithaca NY 14850 domain: jhood@biar.uu.net bang: anywhere!uunet!biar!jhood Looking for a OS hacking programming job in the Ithaca area...
buck@siswat.UUCP (A. Lester Buck) (10/04/89)
In article <307@dksoft.incom.de>, dirk@dksoft.incom.de (Dirk Koeppen) writes: > Does it work to connect a synchronous (4 MB/sec) disk drive and > an asynchronous (1.5 MB/sec) streamer onto the same SCSI bus on > the 386/ix Adaptec 1540 controller ? Does the driver switch the > disk drive into sync. mode or does it use both devices at async > mode ? > > > thanx, > dirk@incom.de Sure, SCSI is downwardly compatible. Everything on the SCSI bus is asynchronous until the (negotiated) data phase, then a synchronous transfer can occur. SCSI-2's wide-SCSI and fast-SCSI are just variations on this theme. The negotiation occurs completely transparently to the driver by an exchange of messages between the device (target) and the host adapter (initiator). You can mix and match asynch and synch devices at will. The one trick is that fast-SCSI is very touchy and all your devices must be rated fast, so you won't be able to mix and match in that case. -- A. Lester Buck ...!texbell!moray!siswat!buck
jr@frog.UUCP (John Richardson) (10/05/89)
In article <307@dksoft.incom.de>, dirk@dksoft.incom.de (Dirk Koeppen) writes: > Does it work to connect a synchronous (4 MB/sec) disk drive and > an asynchronous (1.5 MB/sec) streamer onto the same SCSI bus on > the 386/ix Adaptec 1540 controller ? Does the driver switch the > disk drive into sync. mode or does it use both devices at async > mode ? > > > thanx, > dirk@incom.de If you have enabled the board to allow sync. to work in the initial setup commands, then it will do sync if the target allows it. During each selection to a target, a bit is passed that says wether the target supports sync mode, and the controller uses it. JR
neese@adaptex.UUCP (10/07/89)
Whether or not the 1540 negotiates for synchronous transfers is dependent
on the device and the state of the J1.1 jumper on the 1540. If the J1.1
jumper is installed, the 1540 will negotiate for synchronous transfer
protocol, if the J1.1 jumper is not installed, it is then up to the device
to negotiate for synchronous protocol. Only one device I know of negotiate
for synchronous protocol and it is the HP line of SCSI drives. The 1540
will support a mix of protocols. If one drive will not support synchronous
and the other drive will, then the 1540 will use the correct protocol for
both drives.
This would lead one to believe that the J1.1 jumper should be installed
by default, if the HP drives are the only ones that will do the synchronous
negotiation. This would be great if all devices were really SCSI compatible.
(Sigh) There are some devices that will go into the ozone if an extended
message is sent to the device that the device doesn't support. When this
happens the device is supposed to simply reject the message and go about it's
business. But this is not the case in all devices. The Toshiba CD-ROM will
lose its mind when a synchronous message is sent to it. Some of the early
SCSI drives will do the same thing.
But most of the newer SCSI hard drives will work correctly, and most of them
support synchronous protocol. You'll know reall quick if the device you have
does not support it correctly. Nothing will happen (including boot). If the
drive you have does support synchronous, then you shouild have the J1.1 jumper
installed (unless it is an HP drive). This will yeild about 30% higher
throughput.
Roy Neese
Adaptec Central Field Applications Engineer
UUCP @ {texbell,attctc}!cpe!adaptex!neese
merch!adaptex!neese