Re: SCSI Cable Problem

If the CD-ROM drive works properly when connected internally, but not when
connected externally, that is a pretty sure sign of a SCSI termination problem.

The SCSI HBA (or SCSI host adapter or whatever you want to call it) can either
provide SCSI termination or not. It has to provide SCSI termination when it is
at one end of a SCSI bus. It must not provide SCSI termination when it is in
the middle of a SCSI bus, as with your setup where it sits between internal
devices and an external device. SO check and double check the termination
setting on the HBA, and make sure it does not terminate the SCSI bus.

.... Ben Myers

On Wed, 08 Aug 2007 20:23:36 GMT, "Robert Jarratt" <nospam@xxxxxxx> wrote:


<chrisj.doran@xxxxxxxxxxxxxx> wrote in message
news:1186571576.268200.218300@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On 8 Aug, 00:39, "Robert Jarratt" <nos...@xxxxxxx> wrote:
I bought a generic 50-pin SCSI cable on eBay, with male centronics
connectors at each end, in order to connect an external CD-ROM drive to
my
VAXstation 4000 VLC. The cable does not appear to work correctly, because
if
I connect the same external unit to my VAXstation 3100 M38 it works fine.
The latter machine has a different type of cable with a 68-pin connector
at
the VAXstation end.When I use the non-working cable the console SHOW
DEVICE
command does not list any attached SCSI devices, including other ones I
know
to work otherwise, and it seems to list all the possible SCSI Ids.

I am assuming that this indicates a problem with the cable I bought. Are
there any particular characteristics I should be looking for other than
50-pin centronics? Or do I just have a faulty cable?

Here is the output of a SHOW DEVICE command with the external device
connected on SCSI ID 4 and the internal disk on SCSI ID 2:

VMS/VMB ADDR DEVTYPE NUMBYTES RM/FX WP DEVNAM
REV
------- ---- ------- -------- ----- -- ------
---
ESA0 08-00-2B-2C-90-84
A/2/0
A/2/1
A/2/2
A/2/3
A/2/4
A/2/5
A/2/6
A/2/7
A/4/0
A/4/1
A/4/2
A/4/3
A/4/4
A/4/5
A/4/6
A/4/7
..HostID.. A/6 INITR

SHOW CONFIG output is:

KA48-A V1.2-32B-V4.0
08-00-2B-2C-90-84
24MB

DEVNBR DEVNAM INFO
------ -------- --------------------------
1 NVR OK
2 LCG OK
LR - 8 PLN FB - V1.1
3 DZ OK
4 CACHE OK
5 MEM OK
24MB = S0/1=8MB, S2/3=8MB, S4/5=8MB
6 FPU OK
7 IT OK
8 SYS OK
9 NI ?? 001 0172
10 SCSI ?? 120 0034
11 AUD OK

Regards

Rob

Nice to see my SIMMs installed working :)

You should have something like:

SHOW DEVICE

VMS/VMB ADDR DEVTYPE NUMBYTES RM/FX WP
DEVNAM REV
------- ---- ------- -------- ----- --
------ ---
ESA0 08-00-2B-2B-4A-EF
DKA300 A/3/0 DISK 121.64MB FX
RZ23L 2528
DKA400 A/4/0 RODISK ...... RM WP
RRD40 280E
..HostID.. A/6 INITR




SHOW CONFIG

KA48-A V1.2-32B-V4.0
08-00-2B-2B-4A-EF
24MB


DEVNBR DEVNAM INFO

------ -------- --------------------------

1 NVR OK

2 LCG OK

HR - 8 PLN FB - V1.1
3 DZ OK

4 CACHE OK

5 MEM OK

24MB = S0/1=8MB, S2/3=8MB, S4/5=8MB
6 FPU OK

7 IT OK

8 SYS OK

9 NI OK

10 SCSI OK

3-RZ23L 6-INITR
11 AUD OK




I note that LUN 4 isn't shown in the second list and assume that's
normal, but I haven't booted my VLC to see if it's working.

The long list of A/x/y without DKA200/DKA300 is what I recollect when
the internal disk is not set correctly (dip shunts). Are you using the
original one, or your new non-DEC one? What do you get with the
original and no external disk? Do you have a SCSI terminator (though
it doesn't seem crucial)? I also got an spurious A/4/1 when my cable
wasn't in correctly, so it _could_ be a cable problem. Have you
checked all the connections on your generic cable? Without testing
every pin on mine, it looks as if it should be 50-50 ... 1-1.

BTW your ?? against NI is because the AIU connector isn't terminated.
If you won't be networking the VLC, you need a terminator. I have
loadsa these if you want one.

Chris


Yes, that is indeed your memory installed and working, thanks!

I should have said that without the external unit the machine works fine. I
am able to run VMS from the non-DEC hard disk I installed recently.
Furthermore, if I connect the CD-ROM that is in the external box directly to
the SCSI cable inside the VLC then that works fine too. So, individually,
all the devices I want to use with the VLC work when connected internally.
It is when I connect the CD-ROM externally using the particular SCSI cable
under suspicion that things do not work (just as a reminder, the same
external CD-ROM connects fine to a 3100 when I use the cable that connects
the 3100 to its expansion storage, but that cable has a 68-pin connector at
one end so I can't try it with the VLC). I have tried the cable with and
without a terminator on the other port of the external box.

Of course, I can't connect both devices internally because there are not
enough connectors and not enough space either; I could rig something up but
I have read that the PSU would probably not be up to the job in any case.

I was not aware of the TEST SCSI command, I have been unable to locate an
electronic copy of the VLC's manual (any suggestions?). Here is the output
of the command:

test scsi

?? 120 10 SCSI 0034


84 FAIL

I have tested the cable with my multi-meter and all the pins seem ok. I am
suspicious of the connectors themselves though as much of the body is
plastic and the fit does not feel secure when connecting them to the ports
on the external box and the VLC.

I am aware of the network issue, I have a transceiver that I will be using
to connect the VLC to my LAN, I'll do this when I have fixed the current
problem and have sited the VLC in its new permanent home. What is the effect
of not terminating the AUI port if you are not (yet) networking?

Thanks

Rob

.