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Ask Dave
by Dave Hamilton

He from whom all Mac knowledge flows...

The Meaning Of SCSI, PC-Mac Networks, and Virus Protection
March 18th, 1999

Greetings once again, my friends. Every week you send me some fantastic questions, and this week was no exception. The questions I've answered here are some of the most common questions I've come across in all my years working with computers. If, however, there's a question that I HAVEN'T answered, please send it to [email protected] and I'll get to it right quick!


Gene writes, "Dear Dave: I have an external 2 gig hard drive for my 630CD Performa. It is designated as the startup drive and has the system folder on it. I used to turn it on first for 10 seconds then turn on the Performa and everything worked fine. Now, a year later (beyond the warranty of course), the only way I can get it to power up is to first turn on the Performa, then within a second, turn on the external drive and give it a good tap on the top. It's like if I turn it on and don't hit it I can hear it try to get going but it won't spin up to speed. Is this a power supply problem, "stiction," or something else? I have clean installed the system, run Norton a thousand times, and now my knuckles are getting sore..."

Gene, your second guess is the most likely cause of your problem: "Stiction." I see this often with my clients older machines. For those of you who have never heard this term, let me start at the beginning with my favorite analogy. Think of your hard drive as a record player. It's got a bunch of records stacked on top of each other, and "needles" that read and write to these records. These "records" have a lubricant on them to keep the needles moving smoothly. In time, this lubricant will get thicker and thicker, causing the needles to "stick" in place. What you're seeing is the beginning of the end of that hard drive. When you power up the drive, the "needles" are stuck on the "records" and keep the drive from spinning. A light tap from you jars them loose and once things get moving they're ok. There is no solution for this problem other than replacing the drive, and I recommend you do that IMMEDIATELY. This problem will only get worse, and the day will come when no amount of "tapping" will start up the drive.


Ahmed writes, "Dave, Hello: Appreciate your making the time and efforts to share your knowledge with us. Re: Your column on the Mac-PC network, I have a similar albeit reverse situation. I have a two PC network connected via 3-COM cards and a Asante 5-port hub. One of the PC's is connected to the Internet and the other runs off WinRoute, a proxy server. I also have a Mac (PowerBase) which I would like to get into the network. Is DAVE my only choice so far as needed software is concerned? or are there other options?"

Let's address this network in two parts: file/printer sharing, and Internet access. As far as File Sharing goes, you'll need to get your Mac to "talk" to the PC network. As you mentioned, DAVE from Thursby Software Systems, Inc. does this quite well, and is the solution I recommend. It uses TCP/IP to connect as a standard "Client for Microsoft Networks" and will let you attach to shared folders and printers on the PC side, as well as sharing your Mac resources for use on the PC's. One thing to keep in mind with the Mac is that, for the most part, it can only connect to Postscript printers across this type of network link, so if you have a non-Postscript inkjet printer, the Mac probably won't be able to see it.

As far as Internet access goes, you're already set up, software-wise. WinRoute is not picky as to what type of Operating System is running on the computer -- it only cares about protocols, specifically TCP/IP. Configure TCP/IP on your Macintosh in a fashion similar to the way you have your PC's configured. Set it up for proxy access or IP-masquerading (depending on how you have WinRoute configured) and it will work just fine.


Kent writes, "God am I lost. I have been looking around for the past few months at a lot of different external and internal hard drives. Some cheap and some not so cheap. My question is this. Which kind of SCSI should I use? I understand that my computer( 7300/180 ) comes with Standard SCSI and Fast SCSI. The Fast SCSI is for an extra internal drive. The Standard SCSI is not that fast and most drives that use it are kind of expensive. So now I realize I need to get a SCSI card. Now comes the hard part. Do I get ATA, IDE, Ultra DMA or XYZ? I see a lot of 18 GB drives for $500 and $600 bucks. Is it possible to get one card that will handle all of these or do i need to get one of these types of cards and then get that type of drive. Which is the most economical to get? I am totally lost
with this so any help would be appreciated."

Kent, you do not need to get a SCSI card just to run an external drive. Thanks to all the manufacturers of hardware out there, we have a mass of confusion surrounding SCSI standards and names. With SCSI we have TWO determining factors in deciding the speed and specifications of a drive: Transfer Speed and Data Path Width. "Fast" and "Standard" (and "Ultra") are Transfer Speeds. "Wide" and "Narrow" are Data Path Widths. Your computer supports both Fast and Standard SCSI, but BOTH are Narrow. It's not imperative that you match Transfer Speeds, but it IS important that you match Data Path Widths.

For example, as an external drive, your computer supports "Standard, Narrow" SCSI. This means that it will go 5MB/second maximum. If you put a "Standard, Narrow" SCSI drive out there (which is ALSO rated at 5MB/second) you'll probably get transfer rates of about 2MB/second (because "Standard" drives aren't built to be that fast). If, however, you put an "Ultra, Narrow" drive on there, you'll probably get transfer speeds much closer to 5MB/second since Ultra is rated up to 20MB/second. Of course, you won't be taking FULL advantage of your "Ultra" drive, but they're much more readily available than "Standard" drives, and are pretty cheap, too! If you put that Ultra, Narrow drive inside your machine, you might approach the theoretical maximum Transfer Rate of "Fast" SCSI, which is 10MB/second.

If your using it as a typical "home" machine, you'll probably have good luck adding Ultra SCSI drives to it (I know I did on all of mine here at home) and you don't need to add a card to the machine that supports Wide SCSI unless you're doing audio or video editing and require very high sustained transfer rates.


Joe writes, "Virex has been tracked down as the culprit in a file-copying problem that has cropped up on a computer owned by one of my clients. He is using Mac System 7.5.3 on a Motorola StarMax 300 Power Mac clone. In batch copies from my hard drive to a Zip disk, he is getting -35 and -37 error codes and messages such as "File could not be copied because it could not be found." The files do not appear to be corrupted. When he turns the Virex control panel off, copy problems disappear. Are there any known conflicts involving Virex 5.9.1 and any Mac-related control panels or system extensions?"

I'll be honest, Joe, and say that I haven't seen this particular problem with Virex on any of the machines I manage. In fact, I have found Virex to be the least "intrusive" of all the anti-virus applications for the Macintosh. That said, this brings up a good issue, to which you have already found the only 100%-reliable solution. That issue is in the way that all virus software works: virus software sits right in-between the files on your hard disk and you, the user. It activates before every read from the disk and every write to the disk to make sure what you're reading and/or writing is not infected with a virus. If it finds one, it will alert you and give you the option to remove it, as you would expect. Because of the fact that anti-virus software gets in the middle of EVERY file operation, however, it can interfere with many functions, system-wide. It sounds like the 7.5.3 Finder (or the Iomega Zip driver, quite possibly) is expecting to start getting data from the file immediately when it puts in it's read request for the copy operation. Since Virex activates when that request is initiated, it takes a little extra time for it to do it's virus check and then finally pass the data along to the system, and that pause is what's causing this error (it's reporting "File not found" because it requested it and didn't get it within a specific amount of time). As you've found, the only surefire way to fix this is to disable the Virus-protection software (which is why many software installers tell you to do the same).

In your situation, Joe, I would recommend upgrading to the latest version of IomegaWare for the Zip drive to see if this helps at all, but do expect that all anti-virus software (on both the Macintosh and PC) will cause some problems. That said, I have found Virex to be the best of the bunch.


As always, keep those questions coming to me. As long as you do that, I'll be here next week with your answers! Enjoy!

is President and CEO of The Mac Observer, Inc. He has worked in the computer industry as a consultant, trainer, network engineer, webmaster, and a programmer for most of the last 10 years. During that time he has worked on the Mac, all the various Windows flavors, Be, a few brands of Unix, and it is rumored he once saw an OS/2 machine in action. Before that he ran some of the earliest Bulletin Board systems, but most of the charges have since been dropped, and not even the FBI requests that he check in more than twice a year.

Ask Dave is here to answer all the Mac questions you have. Networking, system conflicts, hardware, you ask it, he can answer it. He is the person from whom all Mac knowledge flows....

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