Subject: Re: Narrowing a wide scsi bus
To: Netbsd-current Users <>
From: =?ISO-8859-1?Q?Timo_Sch=F6ler?= <>
List: current-users
Date: 09/14/2004 20:32:17
>> Hi there.  I have a machine (sparc64) which has a wide scsi controller
>> in it, and a wide SCSI disk, but only a narrow scsi cable.  The cases 
>> for
>> this are difficult to explain, but the disk has a receiver, so I can't
>> simply put a wide cable in.
> What do you mean by a receiver? Do you mean a caddy, plugging into a
> backplane?
>>   Is there a way to tell NetBSD, when booting, to treat a scsibus as
>> narrow, and all the devices on it as narrow, regardless of what they
>> otherwise negotiate?  I looked in docs and on the web, and was unable 
>> to
>> find this.
>>   Any suggestions?
> Narrowness or wideness is a property of the physical SCSI bus itself, 
> not
> of the driver. AFAIK, the only kernel level difference will be that the
> scsibusX attached to the driver will have a maximum of 8 devices (inc.
> controller.) A quick scan through esp_sbus.c, for example, only brings 
> up
> a through special cases for the FAS366 wide SCSI controller over the 
> older
> ESP[12]00 narrow chips, and none of those look like narrow/wide
> specialisations.
> Does NetBSD not see the disk? From the prom, what does probe-scsi or
> probe-scsi-all output? Make sure the drive has an ID<7.
> FWIW, I have wide SCSI devices plugged into a narrow bus with no 
> problems
> using ESP200 SBUS based controller.

one should pay attention of high-byte termination, depending on HBA <-> 
target. sez (last paragraph):

'It is possible to convert a wide bus to a narrow one, with widedevices 
closer to the adapter. To do this properly requires a cable which 
terminates the wide part of the bus. This is sometimes referred to as a 
cable with high-9 termination. Specific commands allow the host to 
determine the active width of the bus. This arrangement is 

mit vorzueglichster Hochachtung/best regards,

Timo Schoeler
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