Collection of Tools & Utilities/Collection of Tools and Utilities.iso/system/csvs.zip/CSVS.DOC

Text File | 1987-04-20 | 29KB | 521 lines

                The Computer Shopper PC Clone Validation Test
                    By Andrew M. Fried & Kenneth McMillen

Introduction
------------
There has never been a better time to purchase an IBM clone microcomputer than
today.   Overseas  production and fierce competition have  made  the  computer
consumer master of the industry.

There  is  generally  one question facing most  prospective  buyers  of  clone
computers,  and  that  is  whether  or not the system  is,  in  fact,  a  true
compatible.

Beginning next month, Comupter Shopper will add another program to its list of
programs  used  to  test a systems compatibility with that of  the  PC.   This
program, called BIOSTEST, invokes almost all of the ROM BIOS calls and  checks
them for proper operation.

The purpose of this article is to discuss the various interrupts available  in
ROM BIOS and how they can be checked for compatiblity.


Interrupt 5 - Print Screen
--------------------------
When  the combination of the Shift-PrtScr keys are  simultaneously  depressed,
the  ROM  BIOS  generates  an interrupt type 5.   This  interrupt  causes  the
contents of the screen to be sent to LPT1:.

Our  test of this interrupt is simple and straightforward.  To begin  with,  a
ROM  BIOS  call is made to determine the current video mode.  Once  the  video
mode is known, the active screen memory is known.

The contents of the current screen are saved into a buffer so that they may be
restored  upon completion of the test.  In order to insure that there  is,  in
fact, something on the screen to print, a series of printable ASCII characters
are  generated  and displayed onto the active screen.   These  characters  are
printed sequentially from chr(32) up to chr(127).

BIOSTEST then generates an Interrupt 5.  It becomes the responsibility of  ROM
BIOS to transfer everything on the screen onto the printer.

Once the interrupt has finished, BIOSTEST restores the screen to its  original
condition and waits for you to press a key to continue.  In order to determine
whether or not the interrupt functioned properly, you must examine the printer
output to see if the pattern appears correct.


Interrupt 10 - Video I/O
------------------------
ROM-BIOS  has a set of routines which handle various video   functions.  These
routines set screen modes, move and find the  cursor's position, select active
graphic  pages,  up/down  scrolling, read/write  characters  with  attributes,
read/write  dots, and color selections. Some of them are practical if  program
speed  is not a problem. However if you wish to do some  fancy  graphics  that
are  quick  then using these routines are not  for you. Their  performance  is
slow as you will see with the dot  testing. The nicer functions are the screen
scrolling  and active  page selection. To take advantage of the  graphics  you
will need  a color monitor.

Before  the test begins it checks to see what type of monitor  you are  using.
If  you  are using a monochrome monitor the program  will only  do  the  tests
which  apply to a monochrome display.  There are sixteen functions  with  this
interrupt.  The test will  step through each one and ask you to press any  key
at  the  end of  each test to continue on to the next one. Some of  the  tests
will   display a pass or fail message while the rest of them require  you   to
look at the screen to verify certain conditions. Each of the  tests will  have
a header at the top of the screen to let you know  what is being tested.

The first test that is tried is the verification of a table  in ROM-BIOS  that
contains video initialization parameters. When  you boot your system or  power
it  on the built in diagnostics look  at the switch settings for  the  monitor
type  and set up the video  card with the correct parameters from this  table.
If  one of the  parameters do not match then the test fails. This table  needs
to  match 100% if you system is to be compatible.

The next test deals with setting screen modes. If you are  using a  monochrome
display  then there is only one mode. For the  color display there  are  seven
different modes. You should see  each of the seven modes set (40x25 BW,  40x25
color, 80x25 BW,  80x25 color, 320x200 color, 320x200 BW, and 640x200 BW).

Using  this next function you can set up your cursor type.  In the  monochrome
mode  your cursor is made up of thirteen lines  whereas in the color mode  you
have  just seven. If you use this  function it needs the starting  and  ending
line.  This test should  display a solid cursor, starting at cursor line  zero
and ending  at seven or thirteen.

The  next two tests position and read the cursor's location.  The  first  test
positions  the cursor at row four, column twelve  and prints the  letter  'X'.
You  need  to verify this by looking at  the screen. The other test  does  the
same  thing and then reads  the location of the cursor which should be at  row
four,  column  thirteen. On the screen you should see the blinking  cursor  at
this position. Press any key when you have finished with each  test.

Function  number  four of this interrupt reads the position of  a  light  pen.
This test was not included since most everyone does  not have a light pen.

Function number five selects the active page to display. To  fully utilize all
of  the memory on the video card IBM included  this function which  gives  you
multiple  pages  of text. In a 40x25  screen mode you have a  total  of  eight
pages of text that you  could flip through if your application takes advantage
of  this.   In an 80x25 mode you get just four since you are  using  twice  as
much  video  memory. This function works only with color displays.   The  test
will  first  use  the 80x25 mode and fill up all four  pages   with  the  page
number. Then the test will ask you to press any  key to flip through the  four
pages verifying that each screen  page is filled with the proper page  number.
If so then this test  passes.

The  next  two tests test the scrolling functions. The first   one  fills  the
screen with text and scrolls up a window of text.  The second on does the same
except it scrolls down a window of  text. If you see this happen then both  of
these tests pass. You  can also see what the character set will look like.

The  next  three tests deal with the character handling  routines.  The  first
will  display  a  test  pattern made up  of  all   the  attribute  capabilites
(underline,  color,  blinking...). The  test will read the  pattern  from  the
screen  and  if  it matches the  test passes. The next test  writes  the  test
pattern  on  the screen  and then it is read back to verify that  the  pattern
matches.  If   so then this test passes. The third test also writes  the  test
pattern  to the screen but without any of the attributes so what   you  should
see  is text displayed normally. A trade off with the  attributes is that  you
have  the underline capability only with  the monochrome and color  only  with
the color display.

Functions eleven, twelve, and thirteen are used for  graphics. Function eleven
sets  the  color palette. The test  should cycle through sixteen  colors.  You
will  need to verify  this. Function twelve handles writing dots or pixels  to
the  screen at a particular row and column. The test should draw a  box on the
screen. To verify that the test did this it will read  back all the dots which
make up the box, please be patient while  the test does this. If they are  all
read  back  successfully  then  the test  passes.  Function  thirteen  handles
reading  the  color  of   a dot at some position.  This  test  should  draw  a
different box  and if the test reads back each dot that the box is made up  of
then the test passes.

Function fourteen handles writing characters to the screen  and is similar  to
the functions describe above which handle  characters. This test uses the same
test  pattern  as used in the  above test. If the