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  #1 (permalink)  
Old 9th January, 2003, 05:28 PM
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One SCSI issue - only 40MBps

So, here`s what I`ve got:
- Segate Cheetah ST39204LC SCSI drive
- 80-68pin converter
- LSI22915A SCSI controller - similar to Adaptec 39160
- 68-pin 5-position Ultra 160 SCSI Cable with an active Terminator
- one 32-bit PCI slot

And here`s what I get:
When the computer boots up and the controller searches for drives, it finds the Cheetah, but it shows max sync 40MB/ss.

In the BIOS the settings for this disk are set to max - 160MB/s.

I`ve tried:
To put the disk in SE mode so that it could get at least 80MB/s. Didn`t work.
Switching the PCI slot. Didn`t work either.
Switching the disc. Tried with another Cheetah that supports u2w. Nope.
Using a different cable. Used a non-terminated 68-pin 3-position Ultra 160 cable. Didn`t work.

I`ve had an Adaptec 29140 for about a year on this computer. And now I bought a controller capable of 160MB/s and got the same results .


What to do?




here`s some info about the disc if helps
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Old 9th January, 2003, 07:38 PM
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In Ultra2 SE mode, the Cheetah 18XL will only run 40MB/sec. The drive itself supports LVD and SE, so you should be ok there.

A couple of questions - does your adapter support LVD? The DIFFSNS line has to be connected at the adapter in order to support this. DIFFSNS is pin 46 on the SCA connector. If this is set wrong, the drive will assume it is on a SE system

The only other thing I could think of is that the J2 option select header has a jumper position for SE, this will also force the drive into SE mode.

Áedán
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Old 9th January, 2003, 10:26 PM
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That`s it. The adapter is without LVD support. Too bad I have three of these adaptors and I intend to use them all for u2w drives. Don`t want to pay 75$ for new ones. Kinda broke for some months now... Any way of soldering it, and if, what exactly to do?
Thanx for the answer dude.
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Old 10th January, 2003, 12:36 PM
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Remembering stuff I've half forgotten here...

It is possible that the adapter supports LVD, but isn't high enough quality to support Ultra160. Let me explain a bit further.

Part of the SCSI negotation phase is something called Domain Validation. It's actually part of the Ultra160 spec. It's job is to ensure that if a device supports Ultra160, the cabling/adapters do as well.

Once the drive has indicated it supports Ultra160 (During the scan of the SCSI bus at boot time), the adapter will write information to the drive's internal buffer at Ultra160. The adapter then reads this information back to ensure that it was received correctly. If the data was garbled, or other errors occured, the adapter then drops down a speed and tries again. It will continue doing this until it finds the highest reliable speed possible over the cabling.

It's possible that your adapters can't handle more than 40MByte/sec due to their design!Hence, I'd be wary of trying to mod the adapter, especially for transfer speeds you're trying to do.

Incidently, I found a company that was offering Ultra320 to 68pin LVD compatible adapters - more details at mcpb.com. I have never used this company so I have no idea about their quality or reliability!

Áedán
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Old 10th January, 2003, 03:09 PM
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Done some research. The adapter is definetily not LVD capable.
This is how a LVD capable adapter looks:
http://www.mcpb.com/assets/auto_gene...g_475a0000.gif

Can`t find a good picture of how mine looks, but I`ll describe it. If you look at the top connection line that goes very near the top line of those 68 pins. It takes a small turn and goes through the 7th pin from the right and then back and straight. Well, on my adapter, it doesn`t. It goes a full straight line all the way. That must be it.
I`ve read some of my disc`s manual and it says that the drive will choose whether to operate in SE or in LVD mode depending on the J2 jumper(which can limit the drive to SE only mode, and mine is off) and depending on the: "voltage state of the I/O DIFFSNS line."

If I am going to solder, what exactly to connect?

I know that it`s quite risky, but I can`t stand it. Bought such a great controller and have 3 SCSI`s (two waiting to be installed) and I will have to run them at 40MB/s.

Btw, the offer at http://www.mcpb.com is very nice. If this won`t work, I guess I`ll be forced to order the adaptors there in the near future.
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Old 10th January, 2003, 07:00 PM
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Found the picture of my adapter. 100% only uw capaple. Here`s the pic.
http://www.weirdstuff.com/objects/ca...ge/img2913.jpg


So, what to solder?
The pin and ground or the pin and 5V? My guess would be 5V, but I`m not doing anything without an expert`s opinion.=)
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Old 10th January, 2003, 07:48 PM
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Quote:
Originally posted by burekar
Found the picture of my adapter. 100% only uw capaple. So, what to solder?

The pin and ground or the pin and 5V? My guess would be 5V, but I`m not doing anything without an expert`s opinion.=)
Pin 16 on the Ultra160 connector is Diff sense. Pin 46 on the SCA connector is Diff sense. These two need to be connected together. They should not be connected to anything else. Remember, this *is* done at your own risk, so you should verify the information I have given you.

The way diff sense works is that each device on the bus connects it to either a pull up or pull down. If any one device pulls the line down to ground, the whole bus switches to SE to prevent damage to electronics. If no device pulls it down, then the bus assumes it's running in LVD.

That's why you don't want to connect the diff sense to ground or 5V - you run the risk that one device will end up in LVD mode, and the rest in SE mode. If that happens, the LVD electronics will become toast.

If the bus still fails it's domain validation check, it will not run at full speed! That reminds me - your terminator is LVD as well, yes?

Áedán
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Last edited by Áedán; 10th January, 2003 at 07:51 PM.
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Old 10th January, 2003, 09:09 PM
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Question

Yes, the terminator is LVD compliant.
Any ideas where to get a pin layout picture for both U160 and SCA on the net? I`m not 100% which pin is 16 and which is 46.
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Old 10th January, 2003, 10:15 PM
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I'm not sure actually. Most of the connectors I've used have had pin 1 marked on them.

Áedán
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Old 11th January, 2003, 02:29 PM
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Ok, I`ve soldered it. Nothing happened. Just the same as it was.

I`ve been wondering why is pin7(Return for DB(1)) on the LVD compatible adapters connected to the main connection that goes to 5V and ground.

Most probably I`ll risk 20$ and order one LVD adapter. We`ll see if it`ll work then.

Real thanx for your help Aidan.
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Old 11th January, 2003, 05:12 PM
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Quote:
Originally posted by burekar
Most probably I`ll risk 20$ and order one LVD adapter. We`ll see if it`ll work then.
Remember that all devices on the bus have to be LVD capable, otherwise the bus will remain SE. It's an all or nothing thing!

Hence, when you test, you need to make sure there's nothing there that's acting SE, which means just the host adapter, the LVD adapter and drive, and the terminator.

Áedán
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Old 24th January, 2003, 04:12 PM
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Ok, just to report how it ended.
I saw a super offer on Ebay for a Quantum Atlas III 10k 18.1GB, bought it and ordered one SCA-160U adapter in the same package from the seller.
Got it, plugged the converter in the Cheetah and works perfectly at 160MB/s. The Cheetah combined with the Atlas that has 8MB cache...
IDE only for storage from now on, because this flyes. Never thought that it will be such a difference.
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Old 24th January, 2003, 04:41 PM
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Glad to hear that you're sorted now!

Áedán
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