SUMMARY: Jumpers on disk drive

Date: Thu Jul 02 1992 - 17:11:20 CDT

I asked a question about how to change the Toshiba MK156FA drive (Emulex
MD21) from sd1 to sd0. Looks like this could be a FAQ. I got a couple of
responses, and managed to get the MD 21 manual. All that is required is
to move the first three DIP switches to OFF and the drive becomes sd0.
Here is a list of responses I received. Thanks to Keff Bacon and Ralph
Merwin for the replies.

Subject: Re: Jumpers on disk drive
Date: Tue, 23 Jun 92 23:06:49 EDT
From: Jeff Bacon <>

> Does anyone have instructions for rewiring the jumpers on a Toshiba
> mk156fa ESDI drive with Emulex md21 controllers. My drive is setup for
> being drive 2, but I can't seem to be able to install the mini-Unix onto

what do you mean drive 2? sd2? this is what I presume.

> it. Can anyone tell me how to setup this drive as my only drive. I
> haven't done this before and don't have any manuals. So, more the detail
> the better.

hmm. maybe this should be a FAQ. the Emulex MD21 controller is the same
jobbie-do they used in the Sun shoeboxes. anyway. scsi address is handled
by the controller, not the ESDI drive. there should be a block of DIP
switches on the controller board, numbered 1-8. SCSI target address is
switches 1-3, according to my trusty manual. MSB is switch 3, LSB is switch 1.

> A related question - Can I install SunOS 3.5 from tape onto a disk that
> has jumpers set for being drive 2 and not 1. I tried many combinations
> when installing mini-Unix

since you want to run 3.5, I will presume you are using a Sun-3,
and thus you want those three switches mentioned above to be OFF. that
should make the drive sd0. if this drive is the only drive on your
system, this is probably what you want it to be.

> from: st(0,0,5)
> to: sd(0,9,1)...

sd(0,9,1), if I recall correctly, should be scsi target 1 logical unit 1,
which on a Sun-3 would really be sd3. sd2 would be target 1 logical unit 0,
or sd(0,8,1).

> but nothing seemed to work. I get errors
> sel: cbsr, bsy never set
> My only alternative seemed to be to reset the jumpers to make the drive,
> drive #1. Any suggestions welcome. The setup is a sun 3/50M with a
> mk156a (141 Mb) drive + 60M tape drive in a sun shoebox.

drive 1 = sd0?

hopefully that steers yo in the right direction, not the wrong.

From: (Ralph Merwin)
Subject: Re: Jumpers on disk drive
Date: Wed, 24 Jun 92 7:38:43 PDT

You can change the drive ID by using the DIP switches on the MD21 board.
The first three switches are the SCSI ID:

                dip switch description

                    1 SCSI ID bit 0 \
                    2 SCSI ID bit 1 these combine for ID 0 - 7
                    3 SCSI ID bit 2 /

                    4 Not used
                    5 512 bytes/sector
                    6 Power on spin-up
                    7 Soft errors reported
                    8 Parity disabled

The default setting is all switches in the OFF position. Adjust switches
1 to 3 to change the SCSI ID.

Good luck.


On my shoebox, the MD21 is located in the middle of the bottom of the box,
in between the power supply and the side-mounted drive. It should be under
the your tape drive bracket, mounted to the drive case. Make sure that you
don't fiddle with the switches on the MT02 board, which looks similar to
the MD21, but is for the tape drive. If you remove the four bolts holding
the tape drive bracket to the case, you should see the MD21 still atached
to the case.

The DIP switches are located on the corner near the LEDs (next to the cables
that go to the drive). You'll probably have to remove the tape drive/bracket.
Mine is not obvious, as it looks like any other black plastic DIP part, but
there little yellow switches on the top. It's labeled 'SW1'. Switch 1 is on
the edge nearest to the LEDs. Turn the three SCSI ID switches to the OFF
position, which is towards the edge of the board (and towards the drive).
This will give you a drive ID of 0.


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