goodin2@pro-charlotte.UUCP (Susan Goodin) (10/21/87)
TECH TIDBITS
SPECIAL ON-LINE SERVICES EDITION P
March through August, 1987 Apple II - Volume VI
APPLE II FAMILY
============================
Keyboard Compatibility
======================
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?
=====================================
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?
=================================
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
===========
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
========================
Interleave - Is it a Secret?
============================
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
=====================
Setting Back the Counter or "I'm Dreaming of Unscrupulous Used Car Salesmen"
============================================================================
Q: Is there a way to erase the count of the pages printed on a LaserWriter and
reset it to 0?
A: No. We know of no way to set the count on the LaserWriter to zero.
Resetting the counter, in any event, is illegal in most states, if not all.
FEATURE ARTICLE
ESD: Electrostatic Discharge - It Kills, It Maims, It Corrupts
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
-------------------------------------------------
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
--------------------------
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
---------------------------------
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?
----------------------------------------------
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.
GOOD NEWS DEPARTMENT
=================================
Overheard at Recent Training Session in Charlotte
=================================================
"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!
====================================
"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
================
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!"
Copyright, August 14,1987 Apple Computer, Inc., East Coast Technical Support.
Permission is hereby granted for the use of Tech Tidbits, in part or in whole,
in any non-commercial publication, or for use by any non-commercial group or
organization or Apple User Group with the following credit: Reprinted from
"Tech Tidbits" with the permission of Apple Computer, Inc., East Coast
Technical Support." Permission to use "Tech Tidbits", in part or in whole,
for
commercial use must first be obtained in writing.
Sue Goodin, Editor-In-Chief.
AppleLink Address: Goodin2
Distributed via ProLine by Goodin2.
Send all feedback to: crash!pnet01!pro-sol!pro-charlotte!goodin2
******************************************************************************
UUCP: [ ihnp4 cbosgd sdcsvax nosc ] !crash!pnet01!pro-sol!pro-charlotte!goodin2
ARPA: crash!pnet01!pro-sol!pro-charlotte!goodin2@nosc.mil
INET: pro-charlotte!goodin2@pro-sol.cts.compatth@dasys1.UUCP (Patt Haring) (10/25/87)
Sue Goodin: If you haven't started receiving a *ton* of email to thank you for posting TECH TIDBITS to comp.sys.apple, I'll be surprised. I'm enjoying the newsletters *very* much and find them chock full of valuable information. Thank you! -- Patt Haring UUCP: ..cmcl2!phri!dasys1!patth Big Electric Cat Compu$erve: 76566,2510 New York, NY, USA MCI Mail: 306-1255; GEnie: PHaring (212) 879-9031 FidoNet Mail: 1:107/132 or 107/222