SCSI adapter pinout required!

[KSP]

Hi All

Trying to repair an old workstation with new(ish) hard drives, but I need to make up a cable adapter to make it all fit together. The new drive has a SCSI 68 pin high density connector (the narrow trapezoidal one) and the workstation requires 50 pin low density (the rectangular one with the central keyway).
I can't just buy an off-the-shelf jobby because I need to manufacture it out of ribbon cable in order to squeeze it in a small chassis.

Can anyone provide me with an accurate and comprehendible pinout drawing for this conversion? Google didn't yield much, or maybe I was just searching for the wrong thing... Who knows.

The workstation is a HP Apollo (9000?) series 700 running some derivative of HP-UX. The original drives are dead and the adapter cables we were given are an absolute abortion held together with potting compound, and don't seem to work as the workstation detects no boot drives.

Any help would be greatly appreciated

[stj]

the 50pin is scsi, the 68pin is wide-scsi.

http://pinouts.ru/HD/info-scsi_pinout.shtml


btw, you can get adapters for what your doing that fit almost flush on the rear of the drive - i'v had some IBM drives that came with them!

[edp]

Search for "hp 5182-4551"

[stj]

http://www.ebay.com/itm/SCA-80-PIN-TO-SCSI-68-IDE-50-Adapter-SCSI-SCA-80-PIN-TO-68-50-PIN-SCSI-Adapter-/252284587727?hash=item3abd554ecf:g:zG0AAOSwwo1XevAp

no good, that's for SCA drives.

[KSP]

Thanks for the replies guys.

I should have stated that this isn't a home job, it's a system controller for, let's say, some top secret equipment 

It's company policy to buy from reputable dealers who will provide traceability certificates, so ebay is out of the question I'm afraid. I was trying to get away with not having to purchase anything. No purchasing means no traceability fuss, meaning DIY jobs are actually preferred (stupid, I know, as anything I make myself is likely to be extremely inferior). I basically wanted to to a pin to pin check of the horrible ones we were given, that's why I needed drawings

[rsjsouza]

You may also want to read some SCSI app notes to be sure these two standards are interchangeable - IIRC 50-pin connectors were for regular SCSI (8-bit) and 68-pin were used in Ultra-SCSI (8-bit, but faster) or Ultra-Wide SCSI (faster 16-bit). One that briefly talks about the differences is SLLA035 and another is this webpage from Adaptec.

[KSP]

I am the mere monkey who does as he is told 

Assumption quite often leads to disaster, but being handed a job to do, the assumption is that the clean-fingered brain boxes have already done the "will it work" part and I'm just supposed to do the jiggery pokery bit...

Some IT dude somewhere managed to recover some data off the old drive and clone it to the new drive, so I'm hoping he already did all of the compatibility figuring jargon.

But as I said, assumption is a cruel and unforgiving mistress. I will do my homework (thanks for the links), and deep down a part of me is hoping that someone earning twice as much as me (at least) was wrong and I get the satisfaction of breaking the news to him 

[helius]

There are a least 8 common parallel SCSI connectors. The different data rates are all compatible because the standard specifies auto-negotiation; the one thing that is never compatible with anything else is HVD (differential drivers at +/- 12V).
This vendor should be able to provide you a certification, although it's otiose for something like a cable adapter.
http://www.memoryx.com/ad68midc50m.html

[macboy]

You may also want to read some SCSI app notes to be sure these two standards are interchangeable - IIRC 50-pin connectors were for regular SCSI (8-bit) and 68-pin were used in Ultra-SCSI (8-bit, but faster) or Ultra-Wide SCSI (faster 16-bit). One that briefly talks about the differences is SLLA035 and another is this webpage from Adaptec.

The 50 pin are "narrow" or just plain SCSI, 8-bit bus.
The 68 pin are "wide", 16-bit bus.
Either can operate at normal (5 MHz), fast (10 MHz), or Ultra (20 MHz) synchronous speeds, or asynchronous. The 68 pin may also be differential (incompatible with everything else) or LVD (compatible with everything except old school differential). Differential is uncommon but LVD is very common. This was used starting with Ultra2, U160, and U320 (40, 80 and 160 MHz respectively, giving 80, 160, and 320 MB/s speeds). AFAIK, all U2/U160/U320 controllers and devices will fall back to normal Ultra speeds without LVD signalling if inter-connected with such devices. There is an issue of termination: Few if any LVD devices has internal termination and depend on a separate active terminator at the end of the cable. By contrast most single-ended (non LVD) devices have built-in selectable termination. Termination is NOT optional. I suspect that the OP's issue is caused not by the adapter but by the new drive's lack of built-in termination which the original drive almost definitely had.

[KSP]

Ah I hadn't considered the termination issue. That's certainly worth looking into, thanks!

[stj]

most drives have onboard terminators if you set the jumper to enable it.

[PaulAm]

Depending on when they were manufactured, the onboard terminators might have been removable resistor SIP or DIP networks, which might or might not be present.  If you see three sets of open socket pins, the terminator is not there.

An external terminator always works, but you might have space problems

Look for a data sheet on the drive you have; it should tell you what you need to know.