TechNotes		June 30, 1995  Vol 1 No 7
Copyright (c) 1995 Dynamic Learning Systems.  All rights reserved worldwide.

Table of Contents
-------------------------
A.	Disclaimer and Cautions
B.	About TechNotes
C.	About Dynamic Learning Systems

1.	DOS and Windows
		The DriveSpace Squeeze
		Understanding Fragmentation

2.	Drives
		Getting Music from the CD-ROM Drive
		SCSI Performance Problems
		CD Storage in the Drive
		Big Drive, Big Trouble

3.	Manufacturers and Parts
		Epson Drivers

4.	Monitors
		Considering a Video Upgrade

5.	Motherboards, Ports, and Busses
		ISA Cards in a VLB Slot
		Computer Loosing Time
		Overclocking an AMD

6.	Viruses and Rogue Software
		Don't Be Fooled by PKZIP 3.0


Disclaimer and Cautions
------------------------------------
	This document is COPYRIGHTED under international law.  This document is provided as an educational service by Dynamic Learning Systems, and is intended to benefit all readers.  Although this document is copyrighted, you may print and re-transmit this document freely, so long as the document is used in its entirety, and credit is given to Dynamic Learning Systems.

	THIS DOCUMENT IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.  The reader assumes the entire risk as to the accuracy and the use of this document.  All PC service and maintenance involves some element of personal risk, as well as risk to the equipment involved.  If you are not comfortable following the information contained herein, refer the work to more qualified personnel.  ALWAYS BACKUP VITAL INFORMATION IF POSSIBLE BEFORE ATTEMPTING ANY TYPE OF SERVICE.


About TechNotes
------------------------
	TechNotes is a compilation of symptoms and solutions for various PC problems.  A new release of TechNotes is released every two weeks.  We welcome your contributions of symptoms, as well as solutions that you have found to your own PC problems.  We also encourage you to contribute enhanced or alternative solutions.  It is our hope to make TechNotes a first-rate tipsheet for PC and peripheral service.  The file name of each TechNote includes its release date.  For example, a file name TN040795 indicates a TechNote (TN) date of April (04) 7th (07), 1995 (95).

About Dynamic Learning Systems
----------------------------------------------
	Dynamic Learning Systems specializes in PC upgrade, maintenance, and troubleshooting topics for electronics/computer enthusiasts and technicians.  We publish The PC Toolbox newsletter.  If you have any questions or contributions for TechNotes, or wish to obtain subscription information for The PC Toolbox, feel free to contact us:

	Dynamic Learning Systems
	P.O. Box 805
	Marlboro, MA  01752  USA
	Fax: 508-898-9995
	CompuServe: 73652,3205
	Internet: sbigelow@cerfnet.com


SECTION 1.	DOS and Windows
============================

THE DRIVESPACE SQUEEZE

Q. A lot of people seem to be using DoubleSpace without problems, but some folks have warned me against using it since it can screw up files on the HDD.  I personally wound up with a bunch of cross-linked files after hastily installing some Windows applications on a drive was configured with DoubleSpace.  What versions should one stay away from (or remove or upgrade) when found on an HDD?

A. Microsoft's disk compression software has had a fairly short but colorful history.  Basically, DoubleSpace was developed as a joint R&D effort with the cooperation of Stac Electronics (the maker of Stacker), and initially released by Microsoft with MS-DOS 6.0.  Unfortunately, the version with MS-DOS 6.0 was indeed fraught with bugs that allowed improper writes to the drive - this often translated into damaged files.  
	Microsoft introduced some fixes and updated into the DoubleSpace version shipped with MS-DOS 6.2, but by then, Stac Electronics launched a lawsuit claiming an infringement of Stac's compression patent(s).  A judge ordered an injunction on DoubleSpace, so Microsoft quickly moved to MS-DOS 6.21 which omitted disk compression.
	Ultimately, Microsoft lost its battle with Stac Electronics, but did sign some licensing agreements which allowed Microsoft to resume shipping a modified disk compression utility which has been called DriveSpace - thus, we have MS-DOS 6.22.  Technically, DoubleSpace no longer exists as a product (and Microsoft does not even support it), but the name stuck, and many users frequently (and inaccurately) refer to DriveSpace as DoubleSpace.
	Today, DriveSpace appears to be a sound and reliable product.  While other compression utilities (i.e. Stacker) can tout more powerful performance and features, DriveSpace remains a remarkable value as an MS-DOS utility.

UNDERSTANDING FRAGMENTATION

Q. Can someone explain to me how a disk can keep getting fragmented?  The machine is an HP DX4-100 running Windows 3.11 and DOS 6.22.  Paradox for Windows and Microsoft office are the main applications used on this machine.

A. To really understand fragmentation, you need to have a feel for the way DOS stores files on a disk.  During DOS formatting, the disk is divided into groups of sectors (called clusters).  When a file is saved, the first cluster is recorded in the file allocation table (or FAT), then that cluster points to the next subsequent cluster, and so on - sort of like the links in a chain.  In this way, a file of virtually any size can be stored on a drive using a minimum of 'housekeeping' space.  Now, when that file is erased, DOS does not actually destroy the data, but rather marks each of the clusters involved in that file as 'free'.  That is why you can 'erase' files much faster than it takes to load them.  When a new file is saved, DOS recognizes those formerly-used clusters as free, and proceeds to store data in them.
	So far, so good.  The aspect of fragmentation comes in because DOS does not care where the clusters composing a file are located - any free clusters will do.  As files are added and erased, DOS will fill the empty clusters wherever they are available.  Thus over time, new files tend to become 'spread out' over a disk.  Spreadsheets and word processors produce many new (and often large) files.  As they are added and erased, fragmentation will eventually occur.  Ultimately, fragmentation is a natural (and unwanted) side-effect of DOS.  The best way to combat fragmentation is to run a good defragmenting utility periodically.


SECTION 2.	Drives
==================

GETTING MUSIC FROM THE CD-ROM DRIVE

Q. My problem is that when I play audio CDs, nothing will play out of my Labtec speakers.  When I play Microsoft Encarta or Bookshelf, sound will play just fine out of the speakers - likewise, .WAV files play fine.  Still, audio CDs will not.  Any ideas?

A. Normally, CD audio signals are not processed as data.  To hear CD audio, there is a 4-pin audio cable that runs from the rear of your CD-ROM drive to your sound card (in addition to the SCSI or other interface cable).  Audio signals passed along this 'audio cable' are mixed into the sound card's output, while the sounds that are produced from computer programs are processed through the sound card from the CPU.  To use audio CDs on a CD-ROM drive, you must have this second cable.  Although once rare, you can now obtain these CD-Audio cables readily from your local computer superstore.

SCSI PERFORMANCE PROBLEMS

Q. I recently managed to get an older SCSI adapter board working, and I have connected a 600MB HDD.  The thing is, the drive is S-L-O-W.  It used to service a UNIX workstation, so I don't think the drive is at fault, but something is wrong in the way the card is talking to the drive (or to the computer).  Sure, it's an old 8-bit adapter, but drive performance is just too slow to blame the adapter.  I mean, copying a few MB can take over an hour!  Any thoughts?

A. From the symptoms you describe, you are experiencing SCSI 'bounce back' - a condition exhibited when no SCSI bus terminators are used on an active SCSI bus.  All versions of SCSI (SCSI-I, SCSI-II, Fast SCSI-II, Fast/Wide SCSI-II, and so on) require termination on each end of the bus.  Termination is a series of resistors that absorb each bit signal to ground in en effort to balance the cable's electrical characteristics, preventing reflection of that data back out onto the bus.  'Bounce back' occurs when termination is missing from one (or both) ends of the SCSI bus.  Essentially what happens in 'bounce back' is that SCSI bus signal traffic actually reflects off of the non-terminated end of the SCSI cable back onto oncoming bus traffic.  While the physics of this phenomenon is a bit complicated, the net result is a data or control signal error caused by the 'collision' of oncoming and reflected data.
  The SCSI adapter's ASPI driver (residing in memory) senses this, and generates a re-transmission sequence (thus re-transmitting the data).  If the data reaches its destination OK, then the ASPI driver moves on to the next piece of data.  If, on the other hand, the 'bounce back' happens again, the ASPI driver tries again and keeps trying over and over until a timeout period is reached.  If no timeout is specified, the re-transmission attempts will continue indefinitely.  This problem results in unbearably slow data throughput.
  What I would recommend is to check your HDD and adapter board for little yellow resistor packs next to the SCSI bus connector.  These resistor packs look either like integrated circuits which are (typically) yellow in color, or little multi-legged resistors that are also typically yellow in color.  In most circumstances, there are three of these yellow terminators ganged side-by-side next to each other just behind the SCSI connector itself (but I wouldn't be surprised if you find a variation on the theme).  If, while looking around your hard drive's SCSI connector, you find three side-by-side empty sockets which look like they can fit an IC or a multi-legged component in them, and that drive is at one extreme end of the SCSI bus (i.e.: it's the last device at one end of the SCSI chain), you've probably just discovered your problem - no termination on at least one end of your SCSI bus.  You then need to obtain and install terminating packs in the drive.

CD STORAGE IN THE DRIVE

Q. Do you know if the CD would be damaged if you left it in the drive for six months?

A. Technically, it is harmless to leave a CD in the drive.  However, it is not uncommon for accumulations of dust to gather on the CD (even the reflective underside), and eventually cause occasional read errors.  It might be helpful to periodically remove the CD and dust it off.

BIG DRIVE, BIG TROUBLE

Q. I just bought a WD 850MB hard drive, and for the last [many] hours, I have been having nothing but problems.  I have an EIDE controller which correctly detects my hard drive's size and geometry, but I cannot get it installed (I do not have a second hard disk).  I can get it to work with OnTrack's Disk Manager utility, but my BIOS will accept the large drive.  I can boot to A: and then use FDISK to partition the disk, but when it reboots it tells me there is no operating system.  What am I doing wrong?

A. Although your hardware may accurately detect the drive's geometry, you should still make sure to configure the EIDE drive with the LBA (Logical Block Addressing) setting in CMOS.  This is really the only way your controller will be able to take full advantage of the drive's size.  Remember that when using LBA, any geometry numbers shown may appear impossibly off - that's normal.  Once LBA is invoked, you should FDISK and reformat the drive again.


SECTION 3.	Manufacturers & Parts
=============================

EPSON DRIVERS

Q. I really need a printer driver for my Epson Action Printer 2250.  Is there an Internet site where I can download updated Epson drivers?

A. SimTel is a mirror site that carries many Epson drivers.  You can FTP files from the SimTel site at ftp://oak.oakland.edu


SECTION 4.	Monitors
====================

CONSIDERING A VIDEO UPGRADE

Q.  I am running a VLB 486 2-66, but I have an EIDE VLB HDD controller I/O card and an ISA video card (a Triton 8900CL).  My question is this: Is it worth investing in a VLB video card?  I wonder if there is any noticeable difference to the naked eye.  I am considering a 1MB VLB video board, but I really am not fond of changing all the drivers if it isn't going to buy me much performance.

A. A well-designed VL bus video board will make a substantial improvement in your video performance.  Conservatively speaking, you can expect to see a 15-20% improvement in VL bus video performance over an ISA video system.  With a well-written video driver, the improvement will be even greater.  See for yourself - Load one the Windows README files into Windows Write and make it full screen (maximize it).  Then just hold the DOWN-ARROW key and watch the text 'creep' up the screen.  Now go to your local computer store with a similar PC and a VL bus video board running and try the same thing.  The difference should be very noticeable - especially at higher resolutions and color depths (i.e. 800x600x256 and up).


SECTION 5.	Motherboards and Busses
===================================

ISA CARDS IN A VLB SLOT

Q. Can anyone tell me if you can use a ISA card in a VLB slot?

A. Since the first few portions of a VL bus slot are essentially ISA bus connectors, you should have no trouble using an 8-bit (XT) or 16-bit (AT) ISA card in a VL bus slot (although that would be a tragic loss of system potential).  However, you can not use VLB cards in an ISA bus.

COMPUTER LOOSING TIME

Q. I have a perplexing problem with my PC - the computer's clock is off by about 30 minutes every day.  I keep setting the time back to what it should be, but by next day, the computer is off by another 30 minutes.. What should I be looking for?

A. There are actually several things that you should check here.  The most likely fault is a weak CMOS backup battery.  Often, a weakening battery will allow time to slip, but still manage to sustain other CMOS parameters.  Try replacing the CMOS backup battery.  Also check any motherboard jumpers related to the CMOS battery to be sure that they are all set correctly.
  Another possible cause of time problems is related to newer 'green' motherboards which employ power-saving features.  Some power-saving functions inadvertently slow clock speeds which may be used by the RTC (real-time clock).  Check the documentation for your motherboard and see if there are ant power-saving functions - if so, try disabling them.  If the problem disappears, you may have to modify the motherboard's power-saving protocol to avoid the time loss.

OVERCLOCKING AN AMD

Q. Will an AMD 486DX40 run properly at 50 MHz?  If so, what precautions are needed?

A. Running a CPU at a frequency faster than its rated speed is a technique known as 'overclocking'.  Unfortunately, it rarely works.  You see, CPUs are sorted for speed by the manufacturer.  AMD has already tested the CPU at higher speeds, but it either failed outright, or proved unreliable - but it worked just fine at 40MHz.  The truth is that the CPU might work at a higher speed, but there is no way to tell.  Problem symptoms may range from occasional lockups to not working at all.  Overclocking also generated large amounts of heat, so the CPU must be properly secured to an adequate heat sink - otherwise it may burn out.  As a rule, don't overclock a CPU.


SECTION 6.	Viruses and Rogue Software
===================================

DON'T BE FOOLED BY PKZIP 3.0

Q. I recently came across a copy of PKZIP 3.0 on a local BBS, but as soon as I tried to use it, files began to disappear from my HDD.  Is this a bug in 3.0?

A. WARNING - you've been duped by a classic Trojan Horse.  There IS no PKZIP 3.0.  The software floating around cyberspace calling itself PKZIP 3.0 will begin deleting files from your hard drive when you try to install it.  PKWARE representatives have confirmed that the latest release of PKZIP is 2.04g.  If you encounter a version calling itself 3.0, report it to the sysop or on-line representative immediately.

