microtech N400 Scsi external harddisk.

That sounds like a perfectly good external (narrow) SCSI enclosure with a Seagate drive inside. It could be an older 50 to 250 MB drive.

The last Mac with a built-in SCSI bus was the Beige G3. But Macs with PCI slots could use an add-on card for SCSI.

daniel,

Here is more about it. External SCSI was one of the greatest things Apple did for its early computers. Apple also charged a premiun price for their computers because they had top quality features like SCSI.

You can disregard the brand name Microtech. It is just a vendor name and vendor company names changed often. The real name to care about is Seagate. Good company. No big complaints to worry about like the Iomega Zip drive "Click of Death." Iomega makes some great products but they will never live down the consumer relations disaster when they were lest than helpful in dealing with a lot of angry customers. A batch of Iomega external SCSI zip drives destroyed data on tens of thousands of customer's zip disks. It was so ugly that state Attorney Generals sued the company to own up to its disaster.

So, on the good side of SCSI, what can you do with your external hard drive and enclosure? First and foremost, use it to make a backup copy of what ever operating system you like best. For example, I like system 7.5.3 better than 7.5.5 or 7.6. I will spare you the reasons why unless you post back and want to know. One quick reason, Apple no longer charges for downloads of 7.5.3.

If it is a larger drive like a 250, you can partition the drive so it will boot several different models of older Macs. We had backup systems of all our different models of Macs on one 4 gig external SCSI drive. Using a school external SCSI drive, our teenage son configured 21 apple computers in a new location in less time than the paid professional adult took to configure one new PC with Microsoft software. Volumes could be written about Microsoft and consumer relations regarding products.

Next, an external SCSI hd can be used to boot many different computers if you use a universal install on your hard drive. Often, people click on the Install button without exploring custom options. If you are installing a new OS on a Performa 200, the software installed might not include files needed by a Quadra 610 DOS or 840AV. Installing a universal system on your hard drive will eliminate the headaches of knowing if your drive will start several generations of Macs.

An example of how useful your hard drive is comes from an experience buying computers from government surplus auctions. People buying used PCs would have to find drivers for video cards, communication cards and any other type of card found in the machine they bought. That process could take them hours or days. Keep in mind, that was back when the internet did not exist as it does today. It was still one of Al Gore's little children, still in grade school.

With an external hard drive like yours, anyone buying a Mac at a government auction could test their purchase in less than sixty seconds. One customized Mac II booted in four seconds. By comparison, the stock version of the 'wicked fast' IIfx took six seconds to boot.

One final note, if you plan on experimenting with a lot of old Macs, set the SCSI id to one. The factory ID setting for internal Apple hard drives is 0. Your hard drive needs a different ID so that it will not conflict with the computer Id. You can take the cover off your enclosure and use it to test many hard drives on one computer. Each hard drive could have a different system for a different generation of processors Options abound.

So, your external drive is like gold when it comes to working on vintage Macs. If you want more information than that, post back. Enjoy.

Jim~

Daniel,

The six wires are nice but not vital. They go to a dial to make it easier to change SCSI ID settings. We can take picture of one of our drives or find a photo online. Meanwhile, here are the pin assignments so you can jump just one at a time and be using the drive. The jumper pins are typically labeled AO, A1 and A2.

No jumper will mean ID 0

First pair only is ID 1 A0 has a jumper.

Second pair jumped is ID 2 A1 has a jumper.

First and second pair jumped is ID 3 A 0 and 2 have jumpers

Third pair jumped is ID 4. A 2 has a jumper

First and third jumped is ID 5. A 1 and 4 have jumpers.

Second and third pair jumped is ID 6 A1 and 2 have jumpers

All three pairs jumped is ID 7 which is reserved as the CPU SCSI device ID for every mac motherboard.

Since all macs that shipped with internal SCSI hard drives had the drive set at zero, jumping any of the pins will give an ID other than 0. Be careful to not use ID 3 because all SCSI CD-ROM drives were shipped having ID three designated. ID 3 takes two jumpers so you cannot accidentally arrive at 3 with one jumper.

Install a jumper on any of the pins, then find, download and open SCSI Probe. SCSI Probe or Apple System Profiler will tell you which number you got. If you do one of the outer ones and get ID 1 then you started from the one end. If you get ID 4, then mark the drive with some tape and indicate that setting one is on the other end. The one in the middle should always give you ID 2, unless the drive has four pairs. Then jump one of the inner two and check SCSI Probe to see what number you got.

Jim~

it still is not simple to let all my scsi disks run (i have several 40Mb to 8OMb, mostly Quantum Pro Drive - and i encounter a lot of problems to let them work

The most common problem is not using a Terminator on the "unused" second port on the enclosure. Each drive (except the one inside the Mac) should have it termination removed or jumpered to OFF, and an external Terminator should be applied.

If you do not have one, try to buy one that has an LED on the Terminator -- the LED lights when power is supplied so that the Terminator can do its job.

7.5.3 vs. 7.5.5

Many system updates were incremental. System 7.5 was a nice improvement over 7.1 but as usual, it came with unfinished business. I am sure someone may have been pushing to get the newer system on the market. By the time 7.5.3 came out, most of the bugs had been worked out. New install disks were readily available to install straight to 7.5.3. System 7.5.5 had minor updates that most of us never needed. It was a two step install. More trouble than it was worth. Plus, the few drives that had 7.5.5 had issues. Who knows if the .5 updates were to blame. The fact that .3 was so trouble free for most of the CPUs it ran led us to quit while we were ahead.