All SCSI expert. Pease help

[Tanker135]

SCSI termination. This has been giving me the big headache. I though I have a good understanding of SCSI termination, but now I am confusing like hell.
I have a Gigabyte board (model GA-6BXDS) with dual channel UW SCSI with Adaptec built in chip set (AIC-7895). The manual is almost clear tell you how to set up in the BIOS for most of the case except in my case (pretty ODD, isn't).

This is what I connect into my computer
a. Plextor 4x12 recorder in channel A (50 pin)terminated in Plextor device.
b. Plextor UltraPlex 40 Wide in channel A (68 pin)also terminated in the device itself.
c. Two UW hard drives in channel B with the last drive terminated.

This is the spec and opitions in my SCSI board
1. Channel A has both UW (16 bit/68pin)and Narrow (8bit/50pin) connectors (one each).
2. Channel B has only one UW connector (16 bit).
3. The options in BIOS for channel A are LOW Byte, High Byte or Disable
4. The options in BIOS for channel B are Enable or DIsable.
5. Also after it passed the POST, you can press <Control -A> to get into SCSI set up utility to set further parameters for the SCSI devices. Every Adaptec SCSI has this set up utility. This has the option to set :Automatic, LOW=OFF/HIGH=OFF, LOW=OFF/HIGH=ON, LOW=ON/HIGH=OFF or LOW=ON/HIGH=ON. For some reason I cannot set to automatic.

My questions is what do I need to set up in questions 3, 4 and 5 for my case. Thanks all for the inputs.

 

[Peter]

I assume you are talking about the _termination_ options.

In general, you need to terminate every signal at both ends. With SCSI adapters, the additional signals of a &quot;Wide&quot; cable can be terminated separately.

For the wide-only channel, set the termination to Enabled if the adapter is at the end of the cable. Terminate the other end of the cable too.

For the other channel, you need to enable both the High and Low byte's termination if you use only one of the two connectors. If you use both the Wide and Narrow connectors, then the Narrow part doesn't end on the adapter and its termination must remain disabled, yet the Wide part ends on the adapter and must be terminated - set to &quot;High Byte only&quot; in that case.

Note that you may never use more than two of the adapter's connectors for one channel.

Regards, Peter

 

[Tanker135]

How about question number 5?
When ever I set for channel A, it set the same thing for channel B. I just don't know why. I have dual channel so it should be independent from the other, right??? I know I have a problem with termination since I put the ultraPlex in to replace my narrow one.

 

[Peter]

I can't answer that (5) in detail, since I've refrained from using Adaptec SCSI adapters quite a while ago. (The reason being exactly that - neverending driver and BIOS issues, and a track record of mysterious reliability problems.) Switched over to using genuine LSI Symbios adapters, or at least adapters with their SCSI chips on them (mostly Tekram brand). No more SCSI problems caused by the host adapter ever since.

Now that of course doesn't help you at all. You need to get yourself a main system BIOS update that incorporates a newer Adaptec SCSI BIOS as well.

Regards, Peter

 

[pjs]

See if there is an updated bios for your SCSI controller.

The scsi adapter channel that is connected to the plextors should have the high byte termination on and low byte termination off.

The scsi adapter channel that is connected to the wide hard drives should have both bytes termination on.

An alternative, perhaps as a last resort, would be to get a 68 pin to 50 pin adapter (wide to narrow adapter) and connect the recorder to it on the same cable that the wide plextor is on. The wide plextor would need to stay at the end of the wide cable and would need to keep its termiation on. This way, both the A and B channels would need to have both of the high and low byte termiation on.

Paul

 

[Peter]

Hello? Tanker's SCSI is onboard, not a separate controller card. Meaning there is no update to the SCSI BIOS unless the mainboard maker cares to produce a new system BIOS that also includes a newer SCSI BIOS.

With onboard Adaptecs, there also is no DIY approach to that, since Adaptec's publicly released SCSI BIOSes do not work for their onboard solutions.

Regards, Peter