SCSI addressing

[u856100]

Hi guru's,

I am currently playing with an HP deskside enclosure that has 8 SCSI ports, 4 of which I am using SE SCSI disks on. These 4 disks are daisy chained in with a cd-rom drive and terminated at the fourth. I am trying to add a tape drive(DAT) to inhabit two of the remaining four SCSI ports. I am however, having problems connecting it! When I allocate a SCSI target address above 6 the system does not acknowledge its existence. I have made the assumption that because my enclosure uses 4 dip switches to set the target address, it supports addressing up to 16, but when I allocate the lowest priority address (8), the system gives me two fingers. I have tried allocating an address below 6 (I used 4) and it works fine.

Cutting to the chase .... how do I find out whether my deskside enclosure supports 16 addresses? is it a manual lookup (that I dont have?), and am I right assuming that the addressing priority is as follows :-
7-->0,15-->8

thanks in advance,

John Bushell

[Marc Dijkstra · Accepted solution]

Hey John, what bus are you attaching this enclosure to? The fact that the switches indicate you can go to 15 makes me assume the disks are WIDE. Are they 68way

Narrow SE -> 0-7
Wide SE/Wide DIFF ->0-15

MND

[Wim Rombauts]

The answer is simple : SE-SCSI supports only 8 devices, adresses 0-7

Address 7 allways is the SCSI adaptor of the computer, so you can only use adresses 0-6.

Other SCSI definitions can support addresses from 0-15.

[harry d brown jr]

Scsi id 7 is usually your card id.

live free or die
harry

[u856100]

Hi Marc,

Thanks for you reply, in fact thanks for everyones reply.

I had the machine set up for me and added the tape drive at a later date. What I found out was that the workstation I was using was a narrow SCSI 2 bus, and this was connecting via a narrow-wide SCSI connector to a 64way wide SCSI enclosure. So the bottle neck was at the workstations SCSI bus!

thanks for your help!
John

[John Bolene]

Normally tape drives are setup at address 2 on the SCSI chain, CDROM at 3, disk drives are normally 4,5,6, and 7 is for the SCSI card itself. ID 1, I can't find anything normally that goes there, any clues?

FYI

[Deepak Extross]

Hey John,
What's with the funky userid?

[Marc Dijkstra]

Narrow SE has the 50Way MicroD or Centro. Generally kept to a 6M bus length SCSI id's 0-7

FWSE/LVD has the 68Way MicroD (and now 68Way UHD/VHD. Bus lenght on FWSE was real short, but LVD allows 12M (I believe!)SCSI id's 0-15

FWD same as FWSE but allows the 25M bus length.

A consideration for a narrow bussed machine connecting to a Wide device is termination, if possible try and utilise a 50-58 way cable with inline termination to terminate the floating lines.

Cheers
MND