SCSI Problem

[pleclair]

Ok, I got here a system running on a Asus P2B-DS motherboard, Atlas 10k hard drive, scsi dat, scsi zip, scsi cdrom and an external scsi yamaha 6/4/24. The trouble is I plugged the 10k on the U2 68pin channel, the zip, dat, cdrom on 50pin, and the yamaha on the ultra wide 68pin external bracket. (which is plugged onto the 68pin uw connector). If i don't plug the yamaha drive, everything works fine. If i plug it, the atlas won't be detected by the 7890 bios. The atlas is terminated, the last device on the 50pin chain is also terminated, and the external yamaha is also terminated. So there should be no problem. Everything has it's own id. There seems to be an issue with the yamaha cdr and the atlas 10k, anyone could help me on that one?

[Target]

Forgive me if this is waaaay off base as I am not familiar with the 7890 controller, but I recall reading about this on the adaptec site when looking into using their 2940 UW controller with a setup similar to what you describe.

Sounds to me like you simply have one too many devices terminated on the wide channel side of the card (the atlas and the yamaha), OR, the scsi card itself is terminated in its bios, and in order to use the external connection, you have to disable the SCSI controller termination in the card bios in order for it to pass data out to the external device.

Clear as mud right? If not, check out the Adaptec site for setup instructions using the 2940 UW. It may even be the same controller you have as I also vaguely recall the 2940 being part of a 78xx series of controler family that they produce.

[Banti]

One problem w/2940u2w is that you must pick 2 of the three plugs to use. I do not know if we (I also have a p2b-ds mobo) have this limitation as well. Sorry, about my lack of knowledge... I only use the 50pin plug.


Good Luck,
Banti

[Target]

I went ahead and dug up my manuals for the Adaptec 2940-UW scsi controller, on the off chance that your 7890 is part of the same 7800 family from Adaptec that the 2940 UW is.

Anyway, though the manual does not go into detail, or provide any reasoning behind it, it did say:

CAUTION: Do not connect scsi devices to all three connectors of an AHA-2940 Ultra wide adapter.

[Target]

Found the reasoning for the warning I quoted in previous message.

Here is what the Adaptec site says:

(Q) Can I use all three adapters on my 2940 at the same time?

(A) No. The internal 50 pin connector is a parallel branch of the lower 8 bits of the wide bus. Using all the connectors creates a "Y" connection instead of the point-to-point bus configuration required for proper operation.


Makes sense, and probably applies to many SCSI cards using the same three adapter configuration. Bummer for the setup you wanted to use eh? Also proves that my first reply was "off base"......DOH! I hate it when I put my foot in my mouth <lmao>. Hope it didn't screw you up.

[This message has been edited by Target (edited 01-12-2000).]

[Bleeding Edge]

Hi, Pleclair.

If the motherboard’s scsi controller chip is equivalent to the 2940U2W, all connections can be used at the same time, however, on the 2940UW, only two connectors may be used.

-From here on, I am assuming the controller is the same as the 2940U2W.-

First off, if you are booting from the SCSI hard drive, it should be set to ID 0. Since the highest priority is 7 (for the controller) the priority of the remaining ID numbers are, in descending order, 6-0 and 15-8. If the SCSI hard drive is not the boot drive, ID 6 should be used. And the remaining SCSI devices should be assigned ID # 5-1 in descending order of importance.

ALL end devices should be terminated.

If the problem is an issue of an outdated SCSI Bios (the MB bios may be intergraded into the system Bios in this case) you need an update. If it is a driver issue, an update is also in order.

However, the problem is your most likely the external cable that is being used for the CD-RW. You are probably using a 68pin to 50pin cable, or, a 68pin to 50pin converter along with a 50pin to 50pin cable, correct?

About SCSI cables and Adaptec controllers-
Most converter cables do not properly terminate the
unused pins. This may cause the cable sensing termination circuit on
the controller to incorrectly terminate the adapter. This could cause
problems such as intermittent or no device detection, system hangs, or
data corruption.

So the solution is to purchase a 68pin –50pin Adaptec cable or one that has proper termination of the “high pins”.
OR
Purchase the ACK-68P-50P-E. This is an Adaptec 68-50pin converter for use with a 50pin to 50pin SCSI cable.

AGAIN, 68-pin to 50-pin external converters are available from other manufacturers, but only converters that actively terminate the High Byte should be used. 68-pin to 50-pin cables are also available through other manufacturers, but most of these cables do not terminate the High Byte, and should therefore not be used.

~Of course, this all assumes that the external Yamaha has a normal 50pin connection.~


[This message has been edited by Bleeding Edge (edited 01-12-2000).]