SCSI Question/Wide Ultra, 50 Pins?

[paulcs]

I have the opportunity to pickup a 18.3 GB UW IBM SCSI drive for about $300.00. The price is right, and the drive could go well with a system I've built with an old Adaptec 2940 UW controller.

The odd thing is, it has a 50 pin interface, instead of the 68 pin interface I'm used to with UW drives. Is this a cause for concern?

Paul
paulcs@flashcom.net

[Brian R.]

The 2940 card should have a 50-pin connector. Use a cable with 50 pins on both ends and this connector. If you have an OEM card with no 50-pin connector, there are 68 - 50 pin adapters for this purpose.

For the 50-pin cable place the HD as SCSI ID 0 on the end of the cable and any CD-ROM as SCSI ID 2 or 3 on an intermediate connector. Go to the IBM website for termination advise. Don't terminate with a jumper unless you can't boot (actually I have had to enable active termination in general).
http://www.storage.ibm.com/techsup/hddtech/hddtech.htm

Also, there may be a jumper connection which enables spin-up (Auto Start). If there is, jumper it otherwise the drive will wait for a spin-up signal from the controller (and never get it).

[This message has been edited by Brian R. (edited 07 June 2000).]

[paulcs]

Thanks Brian. I should of been a little clearer. I've setup a couple of SCSI-only systems before. (In fact, the system I'm working on now is piled onto an Adaptec U2W controller.) I was just wondering if there was a downside to the Wide Ultra 50 pin connector. Am I losing anything, peformance-wise, compared to a drive with a 68 pin interface?

Paul
paulcs@flashcom.net

[Brian R.]

As a general rule, the SCSI 2 drives (50-pin) are slower (spindle speed and access time) than the more modern UW SCSI 3 drives and thus a little slower. For example, I think the SCSI 3 UW were the first IBM drives to have 10k rpm spindle speeds (6.5 and 7.5 ms seek). I'll bet the drive you have is slower than that for specs, but probably only a little. You will see the difference in Windows load time, but not significantly anywhere else (depending of course on your normal applications).

The burst transfer rate is 20 MB/s for the 50-pin drives and 40 MB/s for the 68-pin drives (I may be over-generalizing). This is the major difference. I think the average overall transfer rates in the real world are within 10% of each other (as an estimate).

I would find out just how old the drive is. If it is really old, then the difference in speed may be alot more than I am guessing. Anything less than 5400 RPM for spindle speed will be noticably slower (as a criterion for age).

[This message has been edited by Brian R. (edited 07 June 2000).]

[This message has been edited by Brian R. (edited 07 June 2000).]

[paulcs]

It's a 7200 RPM drive.

The odd thing is IBM is claiming this is an 'ultra wide' drive, which is typically associated with the 68 pin interface. What differentiates it from the 'Ultra' format, which I thought supported the 20 MB/s?

If I buy this drive, I smell yet another adapter in my future. I have a 68 to 50 pin adapter that suppresses high byte. If I were to terminate with a CD ROM, I guess I would need a 50-50 pin adapter with high byte suppression capabilities.

Paul
paulcs@flashcom.net

[Brian R.]

I haven't had the pleasure of using adapters on a SCSI chain, so I can't give advice other than don't do it unless you are forced to. I don't understand why they call it UW either, but I would read the IBM site information. They have a great reference section.

[Chucky Cheese]

paulcs,

do you have the model number?? there might be a "designator" to give a hint. like my cheetahs...st39103lw tell me they have a form factor of 3...capacity is 9.103 gb and that the interface is lvd wide.

from what i know about scsi is that that drive sounds like a narrow device...the only other option is that they built that drive with the 50 pin adapter as part of the drive...which is stupid because then it could never negotiate at 16 bits.

belive your initial assesment...its' a narrow device. i wouldn't put it on a wide bus until you ran adaptects' scsi interragator on it, just so you know.

U2W SCSI RULZ!!!!!!!!!

chucky

[paulcs]

The information on the vendor's site is contradictory (although, if their stock numbers are to be believed, they sold almost 200 today). I really think it must be a narrow device. $306.00 is still a good price, however. I'll have to think about it.

Thanks to both of you.

Paul
paulcs@flashcom.net

[Jake]

U2W SCSI RULZ!!!!!!!!!

You said it, baby! Preach the word!
I love my Cheetah/2940U2W setup.

Paul, I'd choose an UW/lvd/160 (68-pin) drive if I was you (or you could buy a 9.1Gb drive). They might cost a little more but they are worth it. Just thinking about the problems you COULD have if trying to mix devices on the chain with an adaptor. It seems to me like a "band-aid" sollution.

Regards,

Jake

[Brian R.]

I bet the HD will work fine on the 50-pin chain off of the 2940. Don't worry about speed (IMHO). HD speed is one of the most overemphasized portions of desktop performance. Servers are another matter. Consider how much of your time is spent accessing your HD. Virtually none. The greatest amount of time is spent with memory access or processor calculation or video display (depending on the application).

Don't fall into the trap of spending more for the fastest HD. Not worth it. Spend the money on processor or video speed. That's where you spend your time. If you access your swapfile often, the fix is to buy more memory, not a faster HD.

[This message has been edited by Brian R. (edited 07 June 2000).]

[SCompRacer]

Gee whiz, Brian R., after you do all the other stuff, faster hard drives are all thats left to do....

I have used adapters on SCSI with no trouble. Just make sure you get the proper adapter that terminates the high byte when going from 68 to 50 pin though. Did this with a scanner on the 68 pin case out of the UW chain on a P2B-LS. Was last on the chain with other UW devices, no loss of performance at all.
Better off to put your HD on the 50 pin chain though as terminated adapters can be pricey, and the 2940 card has a 50 pin.

The adapter deal would be good if you wanted to use the external output on the SCSI card. You can only use two of the three connectors on the 2940 UW card if I remember correctly. But the hard drive with the terminated adapter would have to be on the end of the chain with the drive itself terminated.

Of course you would never want to do this on a U2W chain.....

This is another great site for SCSI info, http://www.adaptec.com/support/index.html
at bottom of page under other installation tips.

------------------
ASUS P3B-F * P III 500 * 256MB Micron ECC RAM * Two Cheetah LVD's * Barracuda UW * DiamondMAX IDE * Plextor Ultraplex 40max/Plexwriter 12/4/32 * Hitachi IDE DVD * 2940U2W * SB Live * 3Com 905B-TX NIC * 3Com Courier V. Ext. * Hollywood + * Win 98SE, Win 2000 *


[This message has been edited by SCompRacer (edited 07 June 2000).]

[Brian R.]

I agree there's nothing left after the other stuff, I just think upgrading a HD is a poor return for your dollar. High tech mechanical hardware (like HDs) are much more expensive than high-tech electronics, at least today. I just don't get much satisfaction from a slightly faster HD, at least when compared with a fast video card or processor. There's always a 50% faster processor than what I have.

By the way, I have used all three of my connectors simultaneously on my 2940. No problem. Is this supposedly a violation of SCSI protocol?

I have an external scanner on my 68-pin external connection (not at the end of the chain). I used a cable with 68-pin and 50-pin connectors and terminated with a Syquest drive. Do you think I'm loosing something here? Performance of the drive is adequate, but I don't know what to expect from the scanner.

(I can see I'll have to consult you if I ever need to use an adapter)

Ok, I'll bite, why not with an U2W SCSI chain?

------------------
650e PIII @ 806 Mhz w/stock heatsink/fan, ABIT BE6, 256 MB Mushkin PC133 + G400 MAX, CL SB Live with Sennheiser HD-600 headphones, Sennheiser DSP360 Dolby processor, and Shure FP22 headphone amplifier, IBM Deskstar 13 GB ATA66 HD, Adaptec AHA2940 w/uw SCSI, IBM Ultrastar 9ZX 9.1GB 10K UW SCSI HD, WD Enterprise 4360 4.3GB 7.2k UW SCSI HD, Pioneer 303s SCSI DVD, Plexwriter 8/4/32A, Win2K, in a modified Supermicro SC750A case, and a partridge in a pear tree.

[This message has been edited by Brian R. (edited 07 June 2000).]

[paulcs]

My problem is I just can't go bananas upgrading this particular system: a dual PIII 500 (Katmai)/W2K-based system with a rather expensive Asus motherboard. I don't think the motherboard is Coppermine compatible, so upgrading CPU's would be a really expensive proposition. Not only would I have to buy two new CPU's, but I'd have to by a new dual motherboard.

I'm not sure this is the best time to be in the market for a dual-CPU motherboard either. Frankly, I'm a little ticked off with Asus about this (and a whole helluva lot of good that does me).

I use the machine mostly for testing purposes and running Seti clients, two at a time. I needed the IDE drive, and I thought the darn thing was just screaming for a SCSI drive. Of course, given the machine's primary purpose, I suspect our team would benefit more from the CPU/motherboard upgrade.

Paul
paulcs@flashcom.net

[SCompRacer]

Regarding the 2940UW card, I was pretty sure the documentation provided by Adaptec said you should not use all three at the same time. Has been a long time and I have no documentation so I am relying on memory. If you are using it with no problems I must be mistaken.

If you stick a non U2 device on the U2 chain, it defaults to single ended devices and you lose the Ultra advantage.

50 pin SCSI are narrow, or 8 bit devices with low byte and control. 68 pin are wide, or 16 bit devices, with low byte/control and high byte. The high byte is supposed to be terminated to allow connection of a narrow device, or your other wide devices can freak out on you as a SCSI rule is you must terminate the end of the bus.

Only way I figure you dont have a problem is you have no UW 68 pin devices on this chain. True?

As far as my SCSI drives go, I came from a world of high performance and just had to have them. Do I really need them? Nope. But performance is the sum of all it's parts. And like racing, some of the small gains cost big bucks.

[Brian R.]

On the SCSI chains I have the scanner/Syquest (external), CDROM (50-pin) on the 50-pin internal connector, and two 68-pin SCSI 3 HDs on the 68-pin connector.

Yeah, I know about the increasing cost of performance. Computers are just another my-dick-is-bigger-than-your-dick thing (for some people) like hot-rods were when I was growing up. Cars are a bunch more expensive and very prone to breaking. Computers are alot safer. I like a fast computer, but not at any cost. Your rational for getting the HD is certainly justified, I'm not putting anyone down for their opinion. I just advise people against the next generation of faster HDs when other options exist.

[This message has been edited by Brian R. (edited 08 June 2000).]