I need scsi termination advice

[gulliver]

How should I add termination to a BlizzardPPC scsi? Can anyone provide an ebay link to a proper scsi terminator to use with this setup?

This is how the scsi chain will be set:

BlizzardPPC scsi -> 50pin to 80 pin adapter -> 80 pin scsi hard drive (36GB)

So how do I properly terminate it?

[rkauer]

Grab a 50pin SCSI cable with built-in termination, or use an adaptor 50-to-68 and grab a 3x connector with built-in termination.

Set the HD to provide termination power and set it to termination enabled, too. Hope you don't go into trouble using a narrow SCSI controller (Blizzard PPC is narrow) with the wide device (80pin, or SCA, is wide SCSI).

[gulliver]

@rkauer
Thank you for your answer

Can you please point me a 3x connector with built-in termination on Ebay?
I am not planning to use other cable than the default BlizzardPPC one.

Is there a problem using SCA ultrawide hard drives with the BlizzardPPC besides the pin convertion?
Ultrawide hard drives are a hell of a lot cheaper and easier to find for me.

[rkauer]

Since SCA is always 16/32 bits you'll have termination problems. I know 68-pin (SCSI-2) are hard to grab, but they worth the effort.

I was gifted 5 SCSI disks from an IT friend. 4.5, 9 & 18Gb disks. All 68-pins. The 18Gb still is on mine A2000.

I used an SCA80 drive once, it only gave me headaches. That on a A2000 GVP controller with 50 to 68 adaptor, then a rounded 68-pin cable with 5 connectors + active LDV termination and finally the 68-to-SCA80 adaptor. Worked (kind of). But lots of writing errors due bad termination.

So, to spare your sanity, use 50 or 68 pin SCSI only.

So, the best approach is having a 5x SCSI cable (they are very common and cheap) and simply cut out the unnecessary connectors with a sharp scissor.

[Calgor]

http://www.scsita.org/aboutscsi/SCSI...utorial.html#6

You need to terminate the extra lines (upper byte termination) of the wide (80 pin 16 bit) drive if connecting to a narrow (50 pin 8 bit) bus. Else you will have write errors if the drive is over 4GB, which surely it is.

Would be easiest to get a 50 to 80 pin adapter which terminates the extra bytes. The adapter would probably be the device providing the termination power to itself as there is apparently no term power line on the 80 pin connector as it is designed for hotswapping.

But in addition to terminating the upper bytes at the 50-80 pin adapter point, I think the wide bus needs termination at the end of the chain (i.e. your 80 pin drive). And I have read that SCA drives do not provide it. So therefore the adapter should also terminate all lines - which would mean the adapter may only work at the end of the chain. Problem is the description of these adapters never mentions if they do. I did not consider 80 pin drives as 68 pin is easier as the drive can terminate the chain if it is on the end as you can set a jumper on it. I will assume that these adapters do not provide this extra termination as it means they would need to be on end of chain reducing their flexibility.

If the BlizzardPPC SCSI terminates its own end of the chain just like the Blizzard SCSI Kit then that end of the chain is already terminated.

I would suggest a 50 pin cable with 3 connectors connected to the following:

BlizzardPPC (self-termination) ---50-80 adapter with upper byte term (and 80pin drive connected) --- active 50pin terminator

The 50-80pin adapter needs to provide term power to the 50 pin cable (these adapters never say if they do this) and both upper byte termination and supply power to itself. I assume the blizzardppc does not provide term power? (my scsi kit did not successfully provide it and it is not documented if it does in its manual)

Can anyone confirm my advice? I do not use 80 pin drives myself.

@Rkauer

I believe that if your 50 to 68 pin adapter was not upper byte terminated that would have been causing the data errors.

EDIT: I think you would also need to set the jumper on the 80pin drive to operate in SE mode.

[gulliver]

Thanks. Now I fully understand the way I should set up and end my scsi chain.

[Calgor]

The only point of contention I see there is if anything on the chain (blizzard PPC scsi or 50-80 pin adapter) would be supplying term power to the active terminator on the end.

68 pin drive is much easier as the 50-68 adapters usually easier as the 68 pin drive can usually provide term power and on top of that have a jumper to terminator the end of the chain. Term power might also be able to be supplied by some 50-68 adapters.

Comparative scsi chain with 68 pin drive and 50 pin scsi cable with 2 connectors:

BlizzardPPC (self-termination) ---50-68 adapter with upper byte term (and 68pin drive connected with term power and termination jumpers both set)

Good luck and hopefully someone can chime in and confirm for the 80 pin hookup as it is quite complex.

[rkauer]

My suggestion is:

Cable terminator - BlizzPPC with no termination and with 50>68 adaptor - 68pin HD with both termination and termination power enabled

Both the HD and the cable terminators are 32bit, so no problem here. Blizzard PPC without termination since it only terminates the lower bits. So all you need is an Adaptec 68-pin cable with active terminator and the 50-to-68 adaptor.

[Calgor]

Isn't narrow (50) scsi 8 bit, and wide (68/80) scsi 16 bit? Where does the 32bit come in?

EDIT: I see there are some references to 32 bit SCSI around so you can have 32 IDs, wasn't aware of that!

[rkauer]

32 SCSI addresses only when using dual SCSI controllers (they are a few on the market, they have two SCSI headers).

The SCA80 (80 connectors, which around 10 are power) is 16 or 32 bit wide SCSI, pending on the HD model (there is no other wide SCSI devices that I know).

On the Amiga scene there is no hardware for 32bit wide-SCSI, IIRC.