kw_odonian

Question Re. Adaptec 2940uw And Quantum Atlas 10k3

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Call me confused or dumb, but I can't figure out if my old but trusty Adaptec 2940UW will be able to use a Quantum Atlas 10k III drive correctly. They're both 68 pin physical connectors, but the Quantum drive is U160 - can it still be hooked up to this model of adapter? Any help would be appreciated, thanks.

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It will work just fine with the 2940UW. Enjoy ;).

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It will work just fine. The SCSI adapter is limited to 40 MB/s. Although your Atlas can exceed that, I doubt it will affect your computing experience.

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For some reason I had a brain lapse and thought the 2940UW supported Ultra2 transfer rates. Ron_Jeremy is correct, the drives maximum transfer rate will be slightly limited.

As he notes this should not affect performance significantly. The device will also automatically revert from LVD to SE mode so you don't have to worry about that.

If you are genuinely concerned that it may not perform well, U160 controllers are very inexpensive these days. It shouldn't cost you much to pick one up.

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For some reason I had a brain lapse and thought the 2940UW supported Ultra2 transfer rates.

If I recall there was either an Adaptec (or was it Compaq) card that was designed for Ultra2. It was cheaper for people who wanted a cheap card for their SCSI burners.

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The device will also automatically revert from LVD to SE mode so you don't have to worry about that.

Gilbo, I don't think there's any reason for his drive to revert (or use) SE mode. It should be fine running the full 16-bit wide mode. Anyway, this is a fantastic little U160 card for cheap cheap cheap. I've never had any problems with it :)

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Ron_Jeremy,

I think you are getting confused between Single Ended/Low Voltage Differential and narrow/wide...

Narrow SCSI was 8 bit and half the transfer rate than Wide SCSI (16bit)

SE mode :(5 volts)

LVD : 3.3 volts

SE modes :

SCSI 1 was narrow 5 MB/s

fast SCSI was narrow 10 MB/s

fast wide SCSI was 20 MB/s

ultra wide SCSI was 40 MB/s

LVD modes :

Ultra2 narrow 40 MB/s

ultra2 wide 80 MB/s

Ulltra3 or ultra160

narrow 80 MB/s

wide 160 MB/s

Ultra320 wide 320 MB/s

Serial Attached SCSI starts at 3 Gb/s

(by convention B = byte, b = bit)

Hope this helps !

MEJV

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Oh, one more thing about this topic, typical LVD capable drives don't have SE terminators embedded. But they are compatible with SE buses...

Make sure the cable is terminated because I doubt the Atlas 10kIII has any termination at all.

Good luck

MEJV

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Hmm, maybe I did confuse LVD/SE with wide/narrow. My Bad. Anyway, I guess I don't understand why the drive will be reverting to SE mode? I dunno, it's late & I'm tired.

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Re. termination in case the drive drops to SE mode, I have an older SCSI drive with termination I can put at the end of the chain if the Atlas doesn't have termination (haven't purchased it yet, but will do so). That should work, right?

Thanks everyone, for your fast and helpful replies. This board rocks. :-)

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Anyway, I guess I don't understand why the drive will be reverting to SE mode?

The 40MB/s 16-bit, 20Mhz standard that is the highest speed the 2940UW supports is an SE standard. There is a 40MB/s LVD standard, it is narrow Ultra2 (technically it's just Ultra2, but most people think of of Ultra2 as the 80MB/s standard which is 16-bit Ultra2). All Ultra2 (and later standards) use LVD signal transmission. You were confusing 8-bit, narrow, and 16-bit, wide, cable-widths with electronic signalling methods (SE and LVD). There are wide SE devices and narrow LVD devices (although I think all CD-Rom drives ever used the latter protocal).

Ultrawide was the last, and fastest SE standard implemented. Afterwards, the LVD standards took over, beginning with Ultra2.

kw_odonian, mejv is right about needing termination. As long as it's an SE terminator it will work. Also, it will certainly drop to SE mode. Don't worry, you don't have to jumper it; it will do everything by itself.

Enjoy your disk ;).

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You were confusing 8-bit, narrow, and 16-bit, wide, cable-widths with electronic signalling methods (SE and LVD).  There are wide SE devices and narrow LVD devices (although I think all CD-Rom drives ever used the latter protocal).

Gilbo, you're dead on balls accurate. Thanks for clearing that up :)

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Oh, I meant to say, "I think that only CD-Roms ever used the latter protocal (the 40MB/s narrow-LVD/Ultra2 protocal).

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Kind of late to chime in, but seeing as how this drive is one of my products...

The Atlas 10K III will work just fine with a 2940UW. As indicated above, it will be limited to only 40MB/S transfers (UltraSCSI is 20MHz, Wide is 16 bits, 20MHz/Wide is 40MB/S). In this configuration, the drive is running Single Ended SCSI, not LVD. The drive does NOT provide on-board termination, you need to add an appropriate terminator and termpwr.

You want a 2940U2W for Ultra2 and/or a 29160 for Ultra160.

Single Ended and LVD terminators are not interchangable.

Some versions of the Altas 10K III shipped as Ultra320. Depending on when/where you bought yours, you might even want a Ultra320 controller (though you will realize little in additional gains since the dominant limiting factor is the drive's media transfer rate, which is much lower than even 160MB/S).

All Atlas HDDs "sniff the bus" at power on and automatically configure themselves for the fastest rate supported by the configuration they're attached to.

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