Miscellaneous Ramblings

SuperMac S900 Hard Drive Woes Continued

2000.12.19 - Charles W. Moore

In our last episode, your humble servant was left dejectedly contemplating his SuperMac S900, which doggedly refused to boot normally from its Seagate ST32550N hard drive despite protracted efforts by his filial tech adviser.

In the intervening month or so, there has been some progress but no resolution. Following publication of the previous installment of this ongoing saga, I received emails from several readers offering suggestions. You can read them below; thanks to everyone who took the time to write. Special thanks must go to a reader named Lisa, who forwarded a veritable tech info library on Umax SCSI issues, some of which is reproduced below.

I also want to thank Jason C. at Seagate Tech Support, who responded to my query with another compendium of information, which is also excerpted below.

One Friday afternoon, I decided to devote a couple of hours to trying some of the above mentioned suggestions. As it turned out, I was still at it at midnight.

Happily, the big S900 is not too bad to get inside, although to remove the CD-ROM drive it is necessary to remove both sides of the case. It is a testament to the Umax designers that you can remove both side panels and the front panel of the tower by removing just one thumb screw and then pressing a few plastic tabs.

I popped out the CD-ROM drive and the hard drive, then compared their SCSI configuration with the image on Seagate ST32550N Web page and the instructions from Lisa.

The hard drive had originally been set that the default SCSI ID 0 with no jumpers at all on the termination power setting pins. After my son's last battle with the SuperMac, the hard drive had ended up being set at SCSI ID 1 and the CD-ROM drive at ID 0.

This time I decided to return the hard drive's ID to the conventional 0 and the CD-ROM drive to ID 3, as suggested by Lisa. I also put a jumper on the SCSI terminator power pins positioned to take termination power from the SCSI bus, as suggested by Jason C. at Seagate.

At this point, with both the CD-ROM drive and the hard drive laying on the table attached to their SCSI ribbon cable umbilicals, I hit the start button and was rewarded with happy booting sounds from the hard drive. "Ah, it's fixed," I thought hopefully. I pulled the plug, reinstalled the drives in their proper bays, and hooked the SuperMac back up to its monitor and peripherals.

It booted nicely and restarted smoothly several times - until I let it sit for an hour or so, after which it again refused to boot. At this point I was still running Mac OS 9.0.4, and I decided that it might be worthwhile to return closer to the S900's roots. I booted from a CD, then restarted from OS 9.0.4 on the hard drive, which worked fine, as usual, on the restart. I then transferred the installers for Mac OS 8, and the 8.1 update from a Zip disk, then restarted again from the CD, trashed OS 9.0.4, and installed a fresh copy of OS 8.1.

Eureka! The S900 booted nicely from OS 8.1 and continued to do so for the next several days, although there was of course no support for my USB keyboard and mouse. I thought my problems were finally solved, at least sort of, until I got around to putting the case sides back on the machine, which had been running naked since my a jumper adjustments.

Coincidentally or not, at that point the refusal to boot from the hard drive returned. Fine, I decided, at least I'll get USB support back, which I did by dragging a copy of my backup OS 8.5.1 from one of the hard drive partitions on my PowerBook's hard drive onto the Seagate. It still wouldn't boot from cold, but I was able to install Apple's USB Card Support Software Version 1.2 and use my favorite input peripherals again.

And that's pretty much the status quo. In order to get the machine started up, I have developed the following drill: Hit the start button. One of two things will happen; either a "happy Mac" icon will appear, quickly replaced by a blank floppy disk icon; or get a dialogue saying "this disk is unreadable" accompanied by a futile restart button.

In either case, what I do next is insert a bootable CD in the CD-ROM drive, which will then spin up, but not boot. I hit the reset button and immediately press the manual CD - eject button on the drive, which spits out the CD.

At that point, the machine will start to boot from the system on the hard drive, but it will hang before, or more likely just as, the extensions begin loading. I press the reset button yet again, and eight times out of ten the S900 will finally boot from its hard drive normally and give no more trouble until it has been shut off again for an hour or more, after which one must repeat the above process.

The other two times out of ten, even goosing it with the CD (what ever that does) doesn't work, and I end up booting from OS 8.1 on a Zip disk using the command-shift-option-delete key combination. Again, once successfully booted from the Zip disk, it will happily reboot from its hard drive. It also boots from a floppy with no hesitation at any time.

If I were using the S900 has my everyday computer, this would be less onerous, as I could just leave it in sleep mode 24/7 (although my wife complains about the fan noise at night when I have tried this). However, it is my backup machine, and therefore one that I need to start up only once every few days or so.

My next planned step will be to pick up a small SCSI hard drive on the cheap and see if that will work as a "boot disk." Other World Computing has some 500 MB Quantum Fireballs with Apple ROMs for $21.95.

My current hypotheses are that there is either still some undiscovered weirdness in the SCSI configuration, or something either defective or incompatible about the Seagate ST32550N Drive. I'll keep you posted.

The Letters

From Chris:


I was reading your article about the SCSI drive problems and some of your problems sounded familiar. Don't know for sure if ya got the same problem, but I had the same problems with inability to remount my hard drive after the computer sat overnight and such. Kept reformatting things and everything would be just fine. Restart a few times, everything works fine so I'd confidently go to bed. Get up in the morning, and it wouldn't fire up. Norton had a tendency to lose the drive sometimes, too.

This drove me crazy for like two weeks until I checked the internal SCSI ribbon for continuity. Kind of a pain, because there's so many pins to check. It turned out that about half of the cable was showing little or no continuity. I don't really know why it worked at all. After changing out the cable, everything's been fine.

Like I said before, it might not be the same thing causing your problem, but you might want to check it out.

Good luck,

Hi Chris;

When the problem first cropped up, we tried three different internal SCSI ribbon cables, with no difference in results.

Also, the other hard drive we tried boots up fine on the same cable.

Thanks for the suggestion, though.


From Lisa:
Dear Charles,

Re: your SCSI probs. I can attest it's a real pain. I have one of those 9 gig Seagates from hell, it's so big I had to build a SCSI tower just to hold the monster....so I will tell you some things to check on, and at the bottom are some crib notes from an obscure website I found w/lots of Umax info. I hate to send a book, but its complicated. More than it should be.

First thing...driver conflicts. HDT [FWB Hard Disk Toolkit] tries to take over everything, whether it can drive it or not (like the CD), and causes hangs. If you use Intech drivers for CD and HDs, you won't have drivers hanging your SCSI chain anymore. HDT came with my drives, too, but its worth the time, money, and trouble it takes to get rid of it and CDT. I don't use this for a driver 'cause I don't think its OS 9 compatible, but if it scans the chain, it'll will tell you where the problem is...DiskWorks™ v3.4.1. I betcha it says the CD.

1-Make the CD-ROM last on the chain...I set mine at ID 3 and enable term...check the parity and test jumpers cause they were set wrong on some Umax CD-ROMs. The CD-ROM itself could be causing problems. If none of this helps, try a different one and see.

The three pairs to the left set the SCSI ID and should have jumpers on the first two. Still reading from the left there should be a jumper over the fourth pair too to enable parity. Do not enable the fifth pair for termination if a hard disk or other device is connected lower down the same cable. The seventh set of pins from the left (second from the right) enable a Test function. The drive will not work normally when a jumper is installed here. Make sure that test jumper isn't on.

One thing to keep in mind, however, is that the J700, S900, and S910 all have two independent SCSI busses. Apple PCI Macs (e.g., 9500) have a problem with any SCSI devices on ID 5 - use ID 4 instead. And I noticed they still don't like having the same ID number even if they are on separate chains.

Then you get into this messy thing about term power from/to the bus.

Umax says...

Sometimes when a SCSI device that supplies its own termination power is powered down, the Macintosh will still start up because the SCSI bus signal is clean enough for the startup process to take place. However, there is no assurance that the bus signals will stay clean and uncorrupted, since the SCSI bus is not properly terminated in this situation.

SCSI devices that use the termination power provided by the Macintosh do not have to be powered on for the SCSI bus to be properly terminated. The termination power from the Macintosh provides the correct termination to the SCSI bus.

This situation can be confused by the fact that some drives have both "TP" and "TE" jumpers. With such a drive, TP will pass any termination power through to the next device on the chain but will not actually terminate anything; it merely maintains the integrity of the termination signal down the line for whatever eventually will terminate the signal/chain. (We at Umax Computer Corporation can't really think of any reason why one would want to defeat the termination signal at any point along the chain - at least not in a Mac OS system - so the intended value of such a TP jumper is obscure.) In order to actually terminate a device which has both TE and TP jumpers, one must jumper both the TP and the TE positions on that device. Otherwise, with no Termination Power present, Termination Enable has nothing to enable.

In other words, TP should always be enabled. Why didn't they just say so?

So if your drive is in the middle of the chain, you want TP enabled so the signal Passes thru, but not TE, which would End it. See? Ensure the Start Delay jumper is not set. No Delay Motor Start, no Enable Motor Start. Only set the Termination jumper if it's the last physical drive. Set the jumper for Terminate Power from the SCSI Bus.

Most Macintosh computers with SCSI drives provide internal termination power except.... The Mac Plus, Portable, 100-series PowerBooks, 500-series PowerBooks, the PowerBook 1400, and Macs using ATA (IDE) drives do not supply SCSI termination power. See, it's a mess, isn't it?

This IMC place has more info on Umax stuff, but I can't get it to come up right now, so I will include some in case its gone for good.... I have found more info searching Google for "Pulsar" than for Umax. Search for "Gossamer" for beige G3s brings up some amazing stuff in Japan. Those Japanese boys make us look like a bunch of girls. It doesn't bother me, 'cause I'm used to it. Next time you get mad at that Umax, look at that 600 MHz G3 sitting in a Umax S900 running in Japan. If that ICM site doesn't work anymore, let me know and I'll send you all I have on it.



From Support@SEAGATE:
There are several issues why a drive might not boot on your Macintosh type of machine. Software, hardware and firmware problems to name the top three.

First, lets review the hardware configuration to verify the drive is properly setup correctly.

Remember, the following rules apply in general to all types of SCSI systems including Macintosh systems. These steps below should be followed and are the correct way the drive should be configured.
  1. Every SCSI device needs a unique SCSI ID. Verify all devices have a unique SCSI ID.
  2. Every SCSI bus needs termination at both ends of the cable. The SCSI card usually supplies one end of the cable with termination automatically, and the user is responsible for termination at the other end. Most UltraWide and Ultra narrow systems have the last device physically on the cable supply termination by changing the configuration jumper on the drive.
      The ST32550N is an Ultra narrow 50 pin device and has termination settings on the drive. Please see the following link:
      Please see the following link for more information on what is termination:
  3. Every SCSI bus needs termination power. Termination power supplies the active terminator on the drive or the cable, the power needed to terminate the bus. Most SCSI controller cards supply termination power to the bus and the drive does not need to supply. On some Seagate drives such as the ST32250N termination power will need to be configured for "termination power from SCSI bus".
SOFTWARE:Seagate's technical support department is an excellent source for assistance with installation and troubleshooting of your Seagate hard drive. Seagate drives are manufactured to a specific standard (SCSI, ATA,MFM, etc.), not to a specific hardware platform or operating system. If you need assistance with the installation, upgrade, or troubleshooting support for your system or operating system, please contact your system or OS manufacturer or vendor for information specific to your configuration.

The following is an extract from Apple's Tech Info Library:

"Drive Setup: Non-Apple Hard Drive Support

The Drive Setup application is qualified for those hard drives which were shipped by Apple in Apple Macintosh/Power Macintosh computers. While DriveSetup may initialize non-Apple hard drives, Apple is unable to fully test or support issues that may arise from these hard drives. For non-Apple hard drives, Apple recommends that customers use third-party formatting utilities
http://til.info.apple.com/tech info.nsf/artnum/n30572)."

If you are having a problem completely setting up your drive, you will have to use a third-party utility.

To date, the following companies have reported their respective driver versions to be compatible with Mac OS 9 and below:
1. Unfortunately, firmware can not be changed. If this drive is not an Apple compatible drive or a general distribution drive, it may not be able to work. For example a drive that was made for a SUN or UNIX machine will have incompatible firmware on the drive. This firmware can not be changed by Seagate, and you will not be able to use this drive.

Jason C.
Seagate Technical Support