Q: Is it possible to use a MacSE keyboard with a IIgs?
A: Yes. Both keyboards use the ADB (Apple Desktop Bus), and can be used interchangeably. The SE keyboard will work on a new GS or on a //e upgraded to a IIgs.
So Now We're Talking About Shoelaces?
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Q: I've heard the phrase "bootstrap" in reference to the Macintosh, but I've never heard of it with reference to the // family until recently. I assume it's not a reference to shoelaces...what is a "bootstrap?"
A: Bootstrap refers to booting up, or starting up a computer which is accomplished by loading a program into memory from a storage medium such as a floppy disk or hard drive. Often a "boot" or "startup" is accomplished by first loading a small program which then reads a larger program into memory. The program is said to "pull itself up by its own bootstraps", hence the phrase.
Sparse Files - What Does it Mean?
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Q: I recently ran across the term "sparse files" and had never heard the term before. What is it, and what do I need to know about them?
A: A sparse file is one whose logical size is greater than its actual size on the disk. A sparse file contains one or more data blocks which contain nothing but zeroes. While those data blocks are considered to be part of the file, they are not actually allocated on the disk until the zeroes are overwritten by nonzeroes. You can obtain more information on Sparse files in a number of manuals and references, including your DOS 3.3 and ProDOS manuals.
IIgs Trivia
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Did you ever wonder why there is a screw hole on the back panel of the IIgs with no screw in it? Canadian laws require that there be a screw to secure the top cover in place - so it was included in the manufacturing specs to meet that requirement, but it is not used in the U.S. Of course, this provides parents, teachers and dealers with an effective deterrent to discourage unauthorized handling of peripherals installed in the GS!
* * * DISK DRIVES * * *
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Interleave - Is it a Secret?
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Q: What is "Interleave? I keep hearing about it with respect to HD's.
A: Interleave is the ratio of consecutive sectors to which a CPU can read or write. Your SCSI hard drive spins at a steady rate. Depending on what computer you have it hooked up to, the CPU may not be able to read or write to each sector, but only to every 2nd or 3rd sector, and this is where interleave comes in. For example, if you think of your hard drive as a Merry-go-round which never stops, and the data from the CPU as the customers trying to get aboard, you have a fair analogy. One Merry-go-round concession may have a slow ticket seller, and customers get through the line slowly, hopping up on the ride so that every third horse is taken. This would be a 3-1 interleave. The next concession has a faster ticket agent, and the people can get though fast enough to occupy every second horse: This is a 2-1 interleave.
You should always initialize from the type of Mac the drive will be connected to. If you will be using the drive with several Macs, initialize the hard disk for the slowest system. Listed below are the Interleaves for the Mac Plus, SE and II, and Apple II.
Computer Interleave "Speed"
Macintosh II 1:1 "Fast"
Macintosh SE 2:1 "Medium"
Macintosh Plus 3:1 "Slow"
Apple II 3:1 "Slow"
There is an excellent article on AppleLink in the Tech Info Library that you can read called "SCSI Hard Disk Drives: Using them on Different Macintoshes." You can locate this article by using the search word "Interleave."
* * * PRINTERS * * *
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Setting Back the Counter or "I'm Dreaming of Unscrupulous Used Car Salesmen"
1. Once a device or peripheral is safely installed in the computer, it is safe from ESD damage. T/F?
2. You can feel a discharge that is high enough to damage a part. T/F?
3. Air Ionizers will solve most static charge problems. T/F?
4. A component damaged by ESD will fail on a diagnostic test. T/F?
5. "I've been in the computer business for ten years, and I've never seen ESD damage." T/F?
6. You have to actually touch a component before there is a possibility of static discharge damaging the component. T/F?
The answer to all six questions above is FALSE.
ESD is a very major concern for Apple, and you will probably be hearing more and more about it from other areas of the industry as well. Today's high tech components are much more susceptible to ESD than the componentry of bygone years, and, as a result, we are much more aware of ESD related problems than in the past. The simple truth is that ESD may be one of the major causes for some of those "intermittent" problems that plague us all and which are so hard to diagnose. ESD has become more and more of a hazard as microcircuits have become smaller and more sensitive.
Static, or stationary electricity, is electricity that is not moving. It is generated by the separation of two surfaces. One surface is left with a positive charge, and the other with a negative charge. Static electricity is harmless as long as it STAYS static (motionless), but unfortunately, an electrical charge (positive or negative) is unstable, and is always looking for an opposite charge to unite with. Remember those fabric softener commercials? The sock clinging to the sweater? The little "zap" you feel when you walk along a thick carpet and touch someone or reach for a doorknob? The balloon you rub on your clothing to "charge it up" so it will stick to a wall or some other surface? The crackling sound as you pull off a nylon sweater when you're wearing a polyester shirt underneath? The white styrofoam "fill" that clings to everything in sight that is used in packing cases? All of that is static discharge.
The type of static discharge that we are talking about is very small. Most of it you can't even feel. The smallest charge that you feel is 3,000 volts; the smallest charge you can see is 5,000 volts; the smallest charge you can hear is 10,000 volts. But some of the newest semiconductor devices are susceptible to as little as 10 - that's right - TEN volts.
ESD Can Cause Several Kinds of Component Failures
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1. UPSET FAILURE: This is a temporary foul-up that can be corrected by turning the device off and on again, or rebooting.
2. SOFT FAILURE: This failure causes intermittent malfunctioning of the equipment - the most frustrating situation for the customer and the most difficult troubleshooting challenge for the repair technician.
3. HARD FAILURE: A failure that makes the component nonfunctional and unrepairable.
Grounding the Service Area
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Just about the only way to keep static electricity from arcing out of control is to ground all conductive materials in the area. The simple act of shifting your weight from one foot to the other can generate static, so momentary "touch" grounding is not enough - you need continuous grounding such as that provided by a grounded wrist strap and a grounded workbench mat.
The Seven Rules of ESD Prevention
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1. Before working on any device containing a printed circuit, ground yourself and your equipment to an earth or building ground. Use a grounded conductive workbench mat and a grounded wriststrap and ground your equipment to the mat. Made sure you are NOT grounded when working on "live" equipment or when discharging a CRT! Use a Ground/Polarity tester to make sure that your outlets are properly grounded.
2. Don't touch anybody who is working on integrated circuits. If that person is properly grounded, your "zap" will probably not cause any damage, but play it safe and be sure.
3. Use static-shielding bags for boards and chips during storage, handling and transportation.
4. Handle all ICs by the body, NOT the leads.
5. Do not wear polyester clothing or bring plastic, vinyl or styrofoam into the work environment.
6. Never place components on any metal surface.
7. If possible, keep the humidity in the service area between 70% and 90% and use an ion generator.
My Service Area is Secure, So We're OK, Right?
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No. ANYONE who handles the computer, printed circuit board or chips needs to follow safe ESD procedures. This includes the salespeople who may pull out a product to show a customer; the manager who is checking on stock; the people who pack/unpack or otherwise handle products in the stockroom; the customer who wants to see the product. If at all possible, have a mat set up in the stockroom where components can be examined and handled safely. Set one up in your sales area on one of the counters with two wrist straps. One for the sales person, and one for the customer. It's a great way to begin educating your customers to the dangers of ESD! Actively disseminate information to your customers about the danger of ESD and educate them to the proper handling of sensitive components. While touching the power supply on an unplugged computer is not the best insurance against static damage, it is better than no precaution for the customer when he is plugging and unplugging boards in his home.
"Have you been through the MacII Seminar? You should go. The woman who teaches it, Lorna Lowder, is really dynamite. She knows her stuff and keeps things rolling. I wasn't even tempted to fall asleep like I sometimes do!"
Well, We THINK this is a Compliment!
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"Thanks! Somehow I knew that Apple would come through and cut through the red tape. You haven't disappointed me yet. In the words of Dr. Hunter S. Thompson, "When the going gets weird, the weird turn pro!" Keep up the good work and thanks, again."
* * * DEPARTMENT OF FUNNY STORIES * * *
Kids and 'Puters
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One couple was recently rewarded for their teaching efforts in a rather unexpected manner. Their toddler had learned to say "puter and printer" and the parents corrected each such utterance with "COMputer." Finally, the lesson was learned and the toddler proudly announced "COMputer and COMprinter!"
