SCSI questions

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SCSI questions

Are there any clear limitations on what kind of SCSI drives I can use with my Quadra 950 as long as I use an adapter to "adjust" the number of pins? I'm planning on buying some 18GB drives and they are either labeled as simply 80pin, U160 (isn't that 68pin?), or SCA (isn't that always 80pin?). Does it really matter as long as I get the adapter (80 to 50pin or 68 to 50pin)?

Thanks

IC

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As long as the adaptors you b

As long as the adaptors you buy are high-quality, no it doesn't matter.

That said, usally when people are talking about adapting SCA drives for use in non-SCA machines, they're talking about doing it in order to save money, so they're using the cheapest SCA->Whatever adaptor they can find... which results in a lot of heartache for people trying to adapt from SCA.

Also, here's the Lowdown on SCSI pin counts:

50-pin drives are self explainatory. These have some form of Narrow SCSI which the Mac will like on its own.

68-pin drives are some form of Wide SCSI, like Wide, Fast/Wide, UltraWide, Ultra2Wide, U160, or U320. These drives use a 16-bit data bus to transfer half a word in each clock cycle, as opposed to the 8-bit bus that Narrow SCSI uses. Almost all (I believe you have to support this in order to support the full SCSI spec, actually) wide drives can be used on Narrow SCSI busses by terminating the upper byte. The drive can sense this and will go into a narrow-scsi compatibility mode. It usually works to just leave the upper byte floating, and that's how really cheap 68->50 pin adaptors work, but it's not particularly reliable, especially if you're using more than one 68->50 pin adaptor on your SCSI chain.

80-pin SCSI isn't actually a SCSI flavor at all, it's really just a format that SCSI drives can come in. It stands for Sun Connector Architechture and is why most RAID cabinets and also the internal drives in Sun computers don't need any configuration: Those 80 pins provide not only 68-pin SCSI, but also drive power and most of the necessary jumpers, especially the SCSI ID jumpers. That way, you can just take a couple dozen SCA drives, slap 'em into place in your big RAID tower, and be chugging along without spending an hour making sure you don't have a SCSI ID conflict. Smile

80-pin drives aren't required to be 68-pin SCSI, IIRC, so a rare SCA drive that doesn't support Wide might exist. All the same cautions apply to attaching an SCA drive to a 50-pin bus as attaching a 68-pin drive, except that it's even more common for cheap adaptors to cause heartache to those trying to save money.

Go ahead and put those SCA drives into your 950, but make sure you've got a fair bit of time laid out for getting them up and running. Hopefully it'll just work out fine, but you might have to debug something, possibly including replacing some of your adaptors if they're not working well.

Another thing to note is that all modern SCSI drives lack support for termination. I don't remember if the 950's SCSI cable has a terminator at the end or not, but this is important. If the cable doesn't have a built-in terminator, make sure to include at least one native 50-pin drive at one end to provide termination, or attach a SCSI terminator there.

So far, I've been pretty lucky. I've got an 18GB 7200RPM Fujitsu Ultra2Wide drive in my SE/30. I've got a two-connector SCSI cable with a terminator attached to the other connector, and the drive resides on a cheapie, non-terminating 68->50 pin adaptor. It's been very reliable for me despite using that cheapie adaptor. Large file transfers are not any faster, of course, due to the speed limitation of the SE/30 SCSI chipset, but small file transfers are like lightning due to the awesome seek time of the fast drive. You'll love having a fast disk in your 950, since its SCSI chipset is so much better.

To really get your mileage out of the drive, get a SiliconExpress IV or JackHammer NuBus card to get a 20MB/s Fast/Wide SCSI bus in that 950--the disk will be able to start to hit its stride on such a fast bus. The Apple Workgroup Server 95 PDS card might work for you, too, but I don't know if it's supported in System Software or if it requires A/UX. Might be something to check out.

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Ahhha

Thanks a lot TylerS. This has been the best compact SCSI explanation that I have ever seen (and I have looked quite a bit).
I didn't realize that all 80pin drives were actually SCA drives. As a matter of fact I have two 1GB Conner drivers that I bought ~5years ago with adapter for a PowerPC project and they always worked fine. As a matter of fact I have one of those hooked up to the 950 with the system on it. But I think the 950 has an active termination on the internal SCSI bus but not the external one so the termination may not be a problem but I'll keep this in mind.
I'm actually running A/UX on my 950 and would love to find the AWS 95 PDS card but thsoe seem to be hard to come by. I have been looking for a JackHammer card on eBay but without luck. I'll start looking for a SiloconExpress although I'm not sure it will work with A/UX.

Thanks again, this really helped.

IceCap

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One exception...

... that I know of... If you come across a drive that is marked "LVD" -- Low Voltage Differential -- you NEED a matching SCSI interface on the machine. I know firsthand that it's difficult to get these drives to work on non-LVD interfaces, and if you can get them to work, it's only a matter of time (very little time) before the drive goes south, never to return.

I had a pile of very decent 9GB LVD drives that came out of an old RAID tower that had been upgraded with newer & bigger drives, and thought I'd be able to use them as replacement SCSI drives for desktop machines. Nope. The only way I could get them to work reliably was to add a SCSI card that supported LVD drives. The cards themselves were more expensive than new SCSI drives, and I'm not so sure that there is such a card for a 68K Nubus machine.

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What about size?

What about the maximum size the 950 can recognize? I was planning on a 18GB drives but will it be able to recognize 36GB drives?

Thanks

IC

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The 950 will recognize as lar

The 950 will recognize as large of a drive as you care to put into it.

The OS you use will dictate how well it can use those drives, though. If you were running 7.5, an 18GB drive breaks up into 4 4gb partitions and a smallie. a 32GB drive would break into about 9 partitons.

Linux (or maybe A/UX) will take HUGE partitions, so there's the scoop.

The drive in my SE/30 is a LVD drive, but I've had good luck with it.

I think that the proper sacrifice goes a long way towards appeasing the SCSI Gods.

Jon
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It's HVD you want to worry ab

It's HVD you want to worry about. LVD drives can usually be jumpered or are able to auto switch down toa SE mode. Most non-LVD or HCD SCSI is SE. Using HVD drives on a non-HVD bus could burn out the SCSI bus.

JDW
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Re: As long as the adaptors you b

As long as the adaptors you buy are high-quality...

Tyler, do you have example URLs that point to vendors of such high quality SCSI adapters?

For example, this EBAY auction is showing an adapter I've been considering.

It's a 68-pin Wide to 50-pin Narrow SCSI adapter from mcpricebreakers. I've been pondering it so as to put one of my unused Cheetah ST34501W (4.5GB) 10krpm drives in my SE/30. Right now I am using a 7200rpm IBM DGHS-04 (4.5GB) drive. Don't know if there would be any difference in speed though, based on the limitations of the SE/30 chipset. But I would appreciate hearing your thoughts on the "quality" of SCSI adapters and what you're recommendations would be.

Thanks.

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Wow. That one looks a lot bet

Wow. That one looks a lot better than the ones I've used. Smile

I'm an admitted hypocrite when it comes to SCSI adaptors. I always advise everyone to use the best ones they can find, but I use the cheapest ones I can find. Smile My internet server is running off an 80-pin Cheetah 10K.3 (Cheetah 18XL) with a really crappy 80->68 adaptor. Works great!

Really, it doesn't matter which one you use, so long as you've got the guns to troubleshoot any problems you have. If you want it to be bulletproof, you've gotta use good adaptors.

That adaptor looks great to me. Smile

JDW
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Thanks for the feedback, Tyle

Thanks for the feedback, Tyler.

How loud is that Cheetah of yours, but the way! My 4LP is a painful, high-pitched whine. But I've heard the 9 an 18 series are quieter, even at the same 10krpm.

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harddrive decibels

My experience with harddrive noise, ATA and SCSI, is that it really depends on the individual drive and the condition it is in. I've had identical drives with great differences in decibels. Usually, the louder drives are on their way out, but I once had an Atlas IV SCSI drive that was one of the smoothest, sweetest drives I've had, but it made such a shrill sound that I couldn't even stand to be in the room with it for very long. I had to sell it. The buyer seemed happy with it. They say the older you are the less able you are to hear high pitched whines. Maybe that buyer was ancient. I just read how some shop owners who don't want teenagers hanging around their shops have installed devices which put out a faint high pitched sound which annoys teenagers but is inaudible to older people, and they thereby weed-out their clientelle. Pretty clever.

JDW
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SE/30 Quiet Drive Discussion

I have a Seagate ST3120026A 120GB 3.5" drive installed in my G4 Cube. It is so quiet I can't even hear it. Even rapid head movement is hard to hear. But for my old SCSI drives, there is a noticeable whine. While it is true that people over the age of 24 have attenuation in the inner ear for frequencies above 16kHz, the whine I speak of is probably between 8kHz and 20kHz, which means most anyone could detect it regardless of age. If you happen to have a newer quiet IDE drive like my ST3120026A and also an older 10krpm Cheetah, sit them side by side and compare. The ST3120026A will take you to heaven and the Cheetah will whine and dine you to death.

I have simply been told that some of the newer 10krpm Cheetahs are quieter than the older models, but I am curious how "quiet" is defined in that case. My definition of "quiet" is the ST3120026A. I suppose I could just get one of those drives and an IDE to SCSI converter for my SE/30, but it's kind of a waste. I would either need to partition the thing to death or make a couple small partitions and then allow MacOS to ignore everything above 4GB.

Of course, the ultimate would be a flash drive. Manabu Sakai at ARTMIX sells one, but the man refuses to tell me if the speed is roughly the same as a normal hard drive. He obviously knows, but he won't tell. He just goes off on a disertation about theoretical speeds and then says, "buy one and I'll return your money if your not satisfied." Funny, but I'm not satisfied with the answers I've received even before I buy! At any rate, I do wish there was an alternative to ARTMIX for a 50-pin SCSI compatible flash solution. Thoughts?

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Solid state SCSI drive vendor

Solid state SCSI drive vendors...

http://www.memtech.com/memtech_3.5-inch-ide-scsi-solid-state-flash-drives-products.html#memtech-sc3500-side-winder-3.5-inch-scsi-solid-state-flash-drive

http://www.adtron.com/products/S35fa.html

http://www.bitmicro.com/products_edisk_35_scsiw.php

http://www.m-systems.com/site/en-US/Products/IDESCSIFFD/IDESCSIFFD/SCSI_Selection_Guide.htm

Jon
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http://www.bitmicro.com/produ

http://www.bitmicro.com/products_edisk_25_scsin.php

'ello PowerBook drive! Too bad I'm sure they cost more than it's worth thinking about. If someone made a simple, cheap, 128MB-2GB drop in 2.5" SCSI drive, they'd have a quick burst of old PowerBook users buying them up.

JDW
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Gentlemen, Thank you for t

Gentlemen,

Thank you for the numerous links. Sadly, these drives don't appear to be consumer devices as there are no prices or dealer links shown. Indeed, two of the links have a photo in the upper left to make it clear the products on the site are exclusively for medical applications.

The question I have is, do any of you classic Mac owners out there currently have a flash drive installed and working in your classic Mac? If so, what is the link to the drive you have (to the vendor)? And how is "real world performance" (i.e., how fast does it "feel") relative to a normal 7200rpm hard drive?

Thanks!

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Drives

WOW , this thread is taking me way back..
JackHammer controllers, LVD Drives, SCA drives ( make toast in your Mac)...
Flash Drives in an old mac? I love the concept.
Read and Write speeds look great, no internal moving parts,
no noise...cool
Apple just recently invested heavy into 30 GIG Flash Drives.
For Powerbooks, ? Ipods? or DAW's?
Like I said, Cool Idea !
This is all " Future Shock" to me as new macs can use 5 GIGS of RAM, and my 1st Mac had a 50 mb HD.
I say go for it...

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Note

I would suspect that a flash drive would work similar to using a
" RAM Disk" much faster than a HD could ever be.
David

JDW
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I "suspected" the same. But

I "suspected" the same. But in coversations with Manabu Sakai (ARTMIX) about his 50-pin CF drive solution for the SE/30, he went off on tangents arguing about DMA, throughput, speed limit of the SE/30 SCSI interface, etc. Manabu's discussion with me hinted that a flash solution (even one of the fastest CF cards like the EXTREME III) would be slower than a normal hard disk. To clarify, I asked Manabu flat out about his own personal testing. I asked if he could "feel" any performance difference between a normal fast hard disk (7200rpm) and a fast CF card (using his 50-pin SCSI interface). Anyone who has used a computer knows what "feel" means (boot times, double-clicking the main drive in the Finder, speeds to boot commn apps, etc). He refused to tell me this though, nor did he volunteer any benchmark information. Manabu then offered to sell me his device with a money back guarantee, but I turned him down.

Although I've purchased from Manabu before, I am always made uneasy when my direct questions go unanswered. Manabu may be a good engineer, but he is certainly no salesman or PR man! Hence my post here to see if I could discover other user's experiences with flash (not speculation about performance, but real world experience). I'm sure Manabu Sakai has sold at least one of his flash drive solutions, so if any of you own one and use it in a classic Mac (especially an SE/30), please chime in!!

Thanks.

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perhaps get a scsi-ide adapte

perhaps get a scsi-ide adapter and use a large n quiet seagate drive?

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hahaha

hahaha

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Cheetah 10k.3

It's super quiet. Not as quiet as my WD800 IDE drive, but way way way quieter than my 1st Gen Cheetahs (ST34501Ws).

Most hard drives' data sheets list acoustic noise in "Bels (typical)". I'm sure there's the usual jiggery-pokery with manufacturer's testing being BS, but I'm also pretty sure they're all cheating by about the same amount. Smile

So, if you know how loud one drive is, you can use the numbers from that drives' datasheet to compare a known quantity with the unknown other hard drives.

A flash drive? I used one in a PB5300 for a while. It wasn't any kind of special "super fast" CF card, just a normal cheapie one. The access time is way better than anything other than the fastest-spindled hard drives, but the sustained read/write speeds were nothing to write home about.

If you're looking to upgrade from a modern 10k or 15k hard drive, don't even think about it. The access times are actually pretty close, with the edge probably going to the hard drive. If you're upgrading from the Apple 20MB drive you use with your Plus, you'll think your computer died and went to heaven. For something inbetween, like a couple-gigs Quantum Fireball, you'd probably still be good going to flash.

That's just my unscientific feelings about it. I haven't done any testing or anything. I can say from testing and experience that in an SE/30, you'll notice the access time way more than the sustained transfer rate.

The SE/30 maxes out at about 1.25MB/s, which is really slow. Almost any drive can saturate the SE/30 SCSI bus. A drive with a fast seek time will make it feel much more responsive, though. Check out my latest article on LEM to see some serious benchmark numbers on the "Low access time makes old Macs faster" front.

JDW
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Thanks for the detailed reply

Thanks for the detailed reply, Tyler!

So it would seem to be a draw in terms of overall performance among 10k+rpm HD's and flash drives in the SE/30.

I went to both the links you provided but Flaming Tinkerbell didn't take me to it. Not yet posted?

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