SCSI, SCA-to-50, Wide to Narrow, how to terminate high byte

[legacy]

SCA-to-50 adapter


HD50 and HD68 to centronics C50 cables


HD box, for 2 HardDrives


SCSI connectors

hi guys
I have a pair of Seagate ST136475LC SCSI hard drives, they are SCA/80pin, SE/Wide (16bit), and I have to connect them to a Wide Host through a Narrow cable (HD50--Centronics). It does not work at all, while connecting them to a Narrow Host is working good.

• Wide HD/Narrow cable/Narrow Host: not working
• Wide HD/Narrow cable/Wide Host: working

I am using the SCA-to-50 adapter you can see above.

Two more points, it seems that

• the SCSI spec requires drives up to U160 to support narrow transfers, but U320 removes this requirement. So a compliant U320 drive may simply not support narrow operation
• SCA-50 adapters sometimes are just broken by design

When I connect Wide HD/Narrow cable/Narrow Host, I get this error from the HOST controller

Code: [Select]

completion status=0x1e
SCS_AUTO_SENSE_FAILED
scsi status=0x2
state flags=0x3f00
status flags=0x85

I am not able to understand it.



btw, I'd like to see a schematic of a good Adapter SCA-to-50 which uses an high-byte terminator.

[legacy]

Seagate ST136475LC SCSI manual

[macboy]

You will need to force the controller into narrow (8 bit) operation. Otherwise the controller and drive will negotiate wide transfers between them (they both support it so why not?) but that will fail once they try to actually use the upper byte of the bus. If the controller has a BIOS (most bootable SCSI controllers on PC architecture do) then you should be able to do it in there, otherwise it will need to be through the driver or a setting or a config utility.

Personally, I would pull those 50 pin connectors off the back of that box and run the 68 pin ribbon out the back and onto the 68 pin external connector  of the computer. Or run it through a PCI slot into the box to the internal connector.

[legacy]

sgi-scsi-board-with-hd50

You will need to force the controller into narrow (8 bit) operation. Otherwise the controller and drive will negotiate wide transfers between them (they both support it so why not?)

I have installed an HD50 (narrow) connector to the SCSI control board IHD50 (narrow). Unfortunately the board's firmware is not smart and sends a " Wide data transfer request" to the hard drive, it answers "yes, I can speak wide", so they try to talk 16bit each other through an 8 bit cable 

If the controller has a BIOS

It has not, it's for SGI

through the driver

Fujitsu SCSI/SCA harddrives have a pretty jumper "force narrow", while the Seagate has not 

or a setting or a config utility

Irix, the Operating system, does not allow to config anything on that Qlogic board 

Personally, I would pull those 50 pin connectors off the back of that box and run the 68 pin ribbon out the back and onto the 68 pin external connector  of the computer. Or run it through a PCI slot into the box to the internal connector.

The machine does not allow to have other HDs internally, I have to use an external box, and I'd like to share this box with other Narrow machines.

-> I have to buy Fujitsu, it seems, from the Seagate Barracuda's manual, that I do not have other choices 

[legacy]

also the manual says

It is highly recommended that ANSI SCSI-2 Standard’s Alternative 2 termination (active termination) be used for applications with single-ended mode, especially if the bus will be operated at transfer rates above 5 Mbytes/ sec.

Note. ACTIVE TERMINATORS ARE REQUIRED FOR USE IN THE DAISY-CHAIN AS DESCRIBED ABOVE. PASSIVE TERMINATORS SHALL NOT BE USED AT ANY TRANSFER SPEED. ACTIVE AND PASSIVE TERMINATORS SHALL NOT BE MIXED ON THE SAME SCSI BUS.

too bad 

[sync]

Use only 68 pin cables, connectors and a LVD terminator.
Everything else is asking for trouble in your case. The Centronics connectors aren't suitable for high speed SCSI and maybe the Centronics cables are miswired and working only single ended. Also all the nice data corruption due incorrect SCSI wiring...

Irix, the Operating system, does not allow to config anything on that Qlogic board 

Not even by editing some obscure kernel header files and relinking the kernel?
(The IRIX way)

[legacy]

The Centronics connectors aren't suitable for high speed SCSI and maybe the Centronics cables are miswired and working only single ended.

The Hard drive is SE/LVD, but the interface on the host side is only SE, so I have forced the Hard drive to be SE.

Irix can't be configured like linux, I have to forget the Seagate Barracuda and buy Fujitsu

I have 2 workstations
1) SE/Narrow
2) SE/Wide (it does not work LVD)

I need an external HD that can be used by 1) and 2), so the right choice I was thinking was an external HD with the SCSI cables I have posted above.

[sync]

The Hard drive is SE/LVD, but the interface on the host side is only SE, so I have forced the Hard drive to be SE.

What is the maximum speed of the controller?

I have to forget the Seagate Barracuda and buy Fujitsu

And probably running it with 10MB/s bandwidth due the cableing. A NFS mounted NAS could be faster.

I have 2 workstations
1) SE/Narrow
2) SE/Wide (it does not work LVD)

I need an external HD that can be used by 1) and 2), so the right choice I was thinking was an external HD with the SCSI cables I have posted above.

What workstation models do you have?

I have two octanes and a few R10k indigo². But they are collecting dust in the attic.