TechNotes		August 25, 1995  Vol 1 No 11
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. Communications
		Upgrading the UART

2. DOS and Windows
		Understanding the Stack

3. Drives and Displays
		Discolored Displays
		Monitors and X-Rays
		The Missing Drive
		SCSI Without Drivers

4. Manufacturers and Parts
		The NEC Connection
		Finding Award Contacts
		FTP for AMI

5. Memory
		Working With SIMMs

6. Motherboards, Ports, and Busses
		Intel vs. AMD
		Getting Setup to Work

7. Printers
		A Sharp Stylus


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. Communications
=======================

UPGRADING THE UART

Q. I have some communication questions.  What is the normal transfer rate for a 14.4KB modem using the ZMODEM protocol.  I usually use SoftModem with the 19.2KB upgrade, and the rates reported are around 1600-1800 bps during file transfer.  My PC has an older UART chip.  Also, would adding an accelerated UART port (16550 or 16C550) increase the transfer rate?  If so, how would it integrate with the modem?

A. As it turns out, 1600-1700 bps is generally considered as a nominal transfer rate for a 14.4KB modem using ZMODEM as the transfer protocol, so it seems you're right on the money.  You may see this rate drop down if you encounter problems in the communication link.  The advantage of faster UARTS (such as the 16550) is that they typically provide a FIFO (First In First Out) buffer.  The FIFO buffer "buffers" the data flow entering the PC so that data transfers do not demand all of the processor's time - this is a vital function in multi-tasking environments such as Windows and Windows95.  The effect is less noticeable under DOS.
	As for integrating this faster UART, it depends on whether your modem is internal or external.  If the modem is external, you will need to upgrade (or install) a new serial board with a 16550 UART on-board (much cheaper than buying a new modem).  However, if the modem is an internal type, you will need to purchase a new modem containing the advanced UART.


SECTION 2. DOS and Windows
============================

UNDERSTANDING THE STACK

Q.  I have seen the STACKS= entry in CONFIG.SYS often enough, but I'm not sure why it's there or what it's used for.  Can you shed some light on this?

A. The STACKS= command (i.e. STACKS = 9,256) is a feature which allows you to reserve some conventional memory to "store" any interrupt requests until the CPU can get to them.  Most hardware devices in a PC generate interrupts; including your mouse, keyboard, CD-ROM, sound card, and so on.  Whenever you move your mouse, or rapidly press keys on the keyboard, an interrupt is generated for each event.  If your system CPU is busy enough and enough of these interrupts arrive to "swamp" it, you'll get the ever-famous "Stack Overflow" error message.  If this happens while you're in Windows, your PC will instantly reboot.
	In the example above, the STACKS command is reserving 9 stacks of 256 bytes each (approximately 2,304 total bytes of conventional memory).  If that is not enough, you can increase either parameter to arrive at a suitable setting which prevents your PC from rebooting in Windows.  If "9,256" doesn't fix the problem, try "12,256".  You can browse through MS-DOS help (i.e. "help stacks") which should provide valuable information for the maximum values for either of the two parameters.


SECTION 3. Drives and Displays
==========================

DISCOLORED DISPLAYS

Lately, my monitor has been showing discolored areas in the display.  I've considered degaussing the monitor, but I thought that the monitor has automatic degaussing.  Could the auto-degaussing function be defective?

An interesting question.  You have to remember that automatic degaussing is only effective when the monitor is first turned on.  If the monitor is left on all the time (especially in office or industrial environments), the auto-degaussing circuitry never has a chance to work.  Try turning the monitor off and on several times during the course of the day - see if that clears the problem.  If not, try degaussing the monitor manually.  If the problem re-occurs, check the monitor's internal degaussing circuit to see that it is connected and working.

MONITORS AND X-RAYS

I read in an article that the radiation from monitors can promote cancer in children and young adults.  The article suggests being at least 2 feet away from the screen, and NEVER stand behind one.  Is that valid with today's modern monitors?  I'm especially concerned about the "standing behind them" part since I work behind computers a lot.  Thanks for any info.

Well, there's a little bit of truth and fiction here.  When an electron traveling at high velocity (such as the electrons in CRT electron beams) slams against the CRT screen, it liberates radioactive particles.  This has been known and understood since the TV picture tubes of the 1950s.  CRT manufacturers have responded to this by adding lead to CRT glass - especially the front screen.  Under the strict emissions standards currently (i.e. MPR-II) in place, CRTs emit very little radiation from the front screen.  Emissions from the sides and rear of the CRT are also quite low.  The greater danger is in large CRTs which require 30kV or more to excite the electrons.  Over-voltage conditions can allow excessive liberation of X-rays, and over time, there can be a cumulative danger.  You may even have noticed the supplemental X-ray shields around the CRT bell of larger monitors.  As a rule, limit exposure by keeping any radiation shielding in place during operation, and run the monitor only as long as necessary to accomplish your repair or alignment.
	On another note, there's at least one study out that says monitors emit large amounts of positive ions.  Large concentrations of positive ions have been known to cause depression in those who work with computers for prolonged periods of time (i.e. stuck in a cramped office in front of the monitor all day).  If you find yourself stressed this way, improve ventilation in the area, or think about installing a negative ion generator.

THE MISSING DRIVE

Q. I just had a hard drive crash, and had to remove my c: drive.  I turned my D: drive into my C:, and wrote new CONFIG.SYS and AUTOEXEC.BAT files.  I have done this before, so I think I know what I am doing, but when the machine boots, it waits up to 15 minutes between loading MS-DOS and running the boot files.  Someone suggested that I had put in the wrong CMOS settings for the new drive.  Could this be the problem?  Thanks.

A. It does sound as if you might have forgotten to update (or save your changes to) the CMOS setup.  Not only do you have to change the parameters from D: to C:, but you have to mark the D: drive as "not installed".  If CMOS thinks there is still a drive D:, it will attempt to search for it during boot up - of course, if the drive is not there, the system will hang until a timeout occurs, then the system will just continue on.  Try double-checking your CMOS setup data.

SCSI WITHOUT DRIVERS

Q. I am led to believe that a SCSI card of mine can be installed and will work under DOS or Windows without drivers, and that it also has floppy controller support.  If this is so, would you know how DOS/Windows will recognize the card without drivers?  How are the IDs set?  How do you turn on/off floppy control?

A. First, just about all SCSI controllers use an on-board BIOS that provides the instructions which allow SCSI hard drives to work without drivers (depending on your particular SCSI adapter, you may still require a driver to recognize the adapter board itself, but not the hard drives).  When using any other SCSI devices (i.e. SCSI scanners or SCSI CD-ROMs), you will need drivers to run each of those devices.  Of course, you still have to physically set the ID for each device on the SCSI bus.  Floppy controller circuitry can typically be disables or enabled through a jumper on the SCSI adapter.


SECTION 4. Manufacturers & Parts
=============================

THE NEC CONNECTION

Q. Could you please tell me how or where I can find the ftp site address for NEC?  I am having problems galore with this NEC CD-ROM that I bought recently, and I want to find out if NEC has any upgraded drivers.

A. As it turns out, we do have an ftp site on record for NEC.  Try searching for new drivers at ftp.nectech.com.

FINDING AWARD CONTACTS

Q. Do you know if Award has an ftp site?  If not, is there any other contact information you can share with us?

A. While we could not locate an ftp site, you can try Award by phone at 415-968-4433, by fax at 415-968-0274, or by BBS at 415-968-0249.

FTP FOR AMI 

Q. Does American Megatrends, Inc. have a WWW page (or any other internet presence) where I can obtain specifications and other technical information about their motherboards?  I appreciate your help.

A. As far as we can tell, AMI maintains an ftp site where you can download files and documents.  Try them at ftp://american.megatrends.com


SECTION 5. Memory
================

WORKING WITH SIMMS

Q. I presently have 4MB SIMMS and want to upgrade to 8 MB total.  If I add four 1MB SIMMs, does it matter if they are 9 or 3-chip SIMMs?  How about the speed issues? 

A. As far as mixing 3-chip and 9-chip SIMMs, I've seen no problems so far - although if you examine some cheap 3-chip SIMMs, you may see one chip rated faster than the other two - these may cause speed problems if one or more of the chips are too slow for the wait states of your motherboard.
	Where speed is concerned, you should choose SIMMs that are at least as fast as those recommended with your motherboard or system manual (486 and faster PCs often use 70nS SIMMs or faster).  Now, mixing SIMMs of different speeds will typically not cause a problem so long as all of the SIMMs are fast enough to accommodate the system.  If you do choose to mix SIMM speeds, try to place the slowest SIMMs in Bank 0.  This forces the computer to run all the SIMMs at that speed, so no SIMM is forced to run faster than its rated speed.  For example, you can put 70nS SIMMs in the first bank and 60nS ones in the second, and all of your RAM would
run at 70nS.
	A few motherboards can run each bank at different speeds, so this may not always apply.  In this case, all you have to worry about is mixing speeds within the same bank - but just put the slowest SIMM in the first slot, which should make sure the entire bank run at the same (slower) speed.  This would give you a slightly slower system, but most 486 and later systems experience intermittent crashes and memory errors if you try to run SIMMs above their rated speed.  Since SIMMs used in 386 systems are often slower than the SIMMs used in 486 and later systems, a batch of SIMMs that run in a 386 may cause crashes when moved to a 486.


SECTION 6. Motherboards and Busses
===============================

INTEL VS. AMD

Q. Can you explain any differences between the Intel i486DX4/100 and the AMD 486DX4/100.  A friend recently told me that there are some software compatibility problems, but I'm not sure that is true.

A. On the surface, the most noticeable difference between the Intel and Advanced Micro Devices (AMD) processors is that the Intel I486 uses a 16KB internal cache, while the AMD 486 uses an 8KB internal cache.  However, AMD has made extensive efforts to make their line of Intel-compatible microprocessors as functionally compatible as possible with the Intel line.  While there are some features of the Intel processors that are not available in the AMD units, software VERY rarely takes advantage of those features, to instances of software incompatibility are exceedingly rare.

GETTING SETUP TO WORK

Q. I recently purchased a Tandy 3000 PC at a garage sale.  Unfortunately, it has no documentation, and I cannot figure out how to get into the BIOS.  The BIOS is a Phoenix ver1.03.02.  Any ideas about this one?

A. The CMOS setup for a PC is accessed in two ways: through a setup utility on diskette, and (in later systems) a setup utility in the BIOS itself.  When the system first powers up, check the screen display - if setup is available through BIOS, you should see a message on the display indicating the necessary key sequence (i.e. F1 or CTRL+ALT+ESC).  If there is no such message, try holding down a key during power-up - this will trigger a "key stuck" error which sometimes will start a BIOS setup utility.  Now, if neither of these tactics work, chances are that you need a diskette containing the setup utility.  
	Try downloading a generic utility SETUP.EXE from ftp://ftp.firmware.com/ftp/utils/setup.exe.  This utility can be used on systems with BIOS dates before 1987 that cannot be accessed by using regular key sequences on boot up.  I've used SETUP.EXE successfully on many of the 286's or 8088's that I have worked on.  If you would like to check with Phoenix Technologies directly, you can visit their home page at http://www.ptltd.com/phoenix.html.


Section 7. Printers
===============

A SHARP STYLUS

Q. I've been hearing a lot about the Epson Stylus color printer - and it's great output on special paper.  Is the special paper required for all output?  Also, how much do the ink cartridges cost, and how does this printer compare to other color ink jets?

A. Well, we did some investigation on the Epson, and we can tell you that like most ink jet printers, special paper is NOT needed.  The problem is that ink tends to "bleed" into the fibers of ordinary paper, so special "ink jet" papers put a bit of clay into the paper to absorb the ink and prevent bleeding - this results in superior print.  The Stylus can print at 180x180dpi on plain paper, but for higher resolutions (360x360dpi), you should use ink jet paper.  At 720x720dpi, you must use coated paper or the fine detail of your image will be lost in the paper fibers.  Both color and B&W capability are available in all resolutions.
	As far as price and print quality, there are two cartridges: black, and color.  They cost about as much as the HP ink jet cartridges ($15-$25 US).  In 720dpi mode on coated paper, the Stylus print quality is unparalleled among ink jets.  In 360dpi mode, its quality is comparable to HP and Canon ink jets.


