Addon for the documentation

[markus@infoscape.com]

--pgp-sign-Multipart_Tue_Jul__1_16:31:42_1997-1
Content-Type: multipart/mixed;
 boundary="Multipart_Tue_Jul__1_16:31:42_1997-1"
Content-Transfer-Encoding: 7bit

--Multipart_Tue_Jul__1_16:31:42_1997-1
Content-Type: text/plain; charset=US-ASCII

This is a suggested addition to the current documentation; Ken and/or
Gero, please include it in one of the next releases and put it up on
the Web. Feel free to edit this text as required.


--Multipart_Tue_Jul__1_16:31:42_1997-1
Content-Type: text/plain; charset=US-ASCII


There are a couple of common problems with getting an EPROM recognized
by the   PC. First of   all, you should try  to   make sure, that your
network  card, the actual EPROM  chip and the image  file all agree on
the same size. This means, if your image is
  -  8192 bytes long, you need a 2764 EPROM chip and have to configure
     the card to 8kB
  -  16384 bytes  long,   you need a  27128   EPROM chip  and  have to
     configure the card to 16kB
  -  32768  bytes  long, you  need  a  27256 EPROM  chip  and have  to
     configure the card to 8kB.

Some  older cards do not  support 32kB chips, so might  want to try to
get a smaller image  file. You should almost always  be able to create
an image file that fits  into 16kB; if  you use compression and do not
enable all of the features, then you will even be able to build images
that fit into 8kB. As a general rule, it is preferable to have smaller
images,  because  this will  leave  more buffers for DOS;  under Linux
there is (usually) no noticeable difference.

Sometimes, you might be unable to  actually get hold  of an EPROM with
the required size. Nowadays, 27256 EPROMs seem  to be the most popular
and anything smaller  than  this might be  hard  to find. As  the 27xx
series  of chips  was designed to    be backwards compatible,  you can
almost always replace a 27256 for one of the smaller chips. If you are
extremely unlucky, this might not work, with your equipment, but it is
at least worth a  try if you  cannot otherwise  get any 2764  or 27128
chips.

There are a couple of  things to watch  out for, though, if you intend
to substitute  the  EPROM with one  of  the bigger models.  The bigger
EPROMs have  one or  two additional address  lines. Depending   on the
layout of your network card,  these  additional lines might be  pulled
high, low or left floating. Thus the best solution is, to create a new
image that has exactly the same size as the EPROM by attaching several
copies  of the original image  file to each  other. E.g. if you had an
image called "ne.rom"  that was 16kB,  but you want to  burn it into a
32kB EPROM you would do "cat ne.rom ne.rom > ne-27256.rom".

You  should now configure the  ethernet card as  if you  were using an
EPROM that is exactly  the same size as the  original image. So in the
above example, you  would configure your  card for an 27128 EPROM even
though you actually plug in a 27256 chip.

After burning  the EPROM and  configuring the network card, you should
be all set to boot from the card. If this does  not work though, there
are a couple of suggestions for locating possible problems.

Use your EPROM burner to  read out the contents of  the EPROM and make
sure,  that it  actually   contains the data   that  you  want it   to
have. Compare the data against the original image file.

Start DOS and launch the "debug" application. Try  to locate the EPROM
and try to read its contents. Typing '?' will give you a brief summary
of  the commands. Usually, the EPROM  will be  mapped somewhere in the
address range from 0xC8000 to 0xE8000. DOS uses segmented adresses, so
you   will    have  to   specify  these     numbers  as  C800:0000  to
E800:0000.  Please note, that the  first number contains _four_ rather
than _five_  digits. Just strip of  the  last digit, if  your ethernet
program uses the five digit notation.

E.g.  if you  expect the  image to be  mapped at D000,  you would type
"d D000:0000".  You should now see  a hexdump that corresponds  to the
first few  bytes of the ROM  image file. You can  use the UNIX command
"od  -tx1 ne.rom" to verify  that the values  are actually correct. If
you do not find the EPROM image anywhere,  then you should test if you
are  using the  "debug"  command  correctly; verify  the   contents at
address C000:0000.  This is, where graphics cards put their ROM image;
you can probably read some kind  of copyright message within the first
few lines  of the memory dump.   After successfully locating the start
of  the  boot image, you  can   now check that it    is mapped all the
way. Assuming  that  you  have a 16kB  image   that starts at  address
D000:0000,  the last used address would  be D3FF:000F. As the last few
bytes of the  image might be  unused, you might want  to check from --
say -- D300:0000  to D400:0000.   You do  this by typing  "d D300:0000
1000".

If you  do not find the  image at all, or if  there are errors  in the
data, then  the first thing  to  check are  your  BIOS settings.  Some
motherboards can map  RAM into the  space where you  would want to map
your EPROM.  Make sure that this is  not happening.  Also, even though
you ideally want  the EPROM to  be cached,  some  motherboards seem to
have  problems with this  configuration. It  might  be worth  a try to
disable caching for this memory range. If you believe that all of your
BIOS settings are correct, then the next  thing to check is that there
are no  other   extension cards   that try  to  use  the  same  memory
space. Some network cards come with test programs that try to discover
those problems, but this  does not always  work reliably. If in doubt,
remove  all other unneeded  extension  cards and  see if  that makes a
difference.   If you  use  a network card, that  can  be accessed in a
memory mapped mode (e.g. WD80x3 cards), then make sure that you do not
map  the    RAM buffer  into    the  same  space as   the   EPROM data
(incidentally,  make sure that the  RAM buffer is  never cached by the
motherboard).  Some cards  can be run  both in NE2000 and WD80x3 mode;
these cards  have   been reported to  not   map any   EPROM data  when
configured in WD80x3 compatibility mode.  With most  cards you need to
explicitly  enable  mapping of the  EPROM,   so double-check that this
feature is turned on. If all of this fails, try  to get a faster EPROM
chip. Usually,  EPROM chips that are at  least as fast as 150ns should
be OK; chips  that only do 250ns will  probably have difficulties with
some motherboard designs.

If you discover that  none of these suggestions  were helpful  in your
particular case,  then try to collect  as much information  as you can
and report to the mailing list and/or the authors. We will try to help
you directly and then update this document accordingly.


--Multipart_Tue_Jul__1_16:31:42_1997-1
Content-Type: text/plain; charset=US-ASCII

--
Markus Gutschke                         Internet: markus@infoscape.com
Infoscape, Inc                          Phone:    +1-415-537-3778
657 Mission Street, Suite 200
San Francisco, CA 94105

Disclaimer: The above message represents my personal opinion; It does
            not constitute an offical statement by Infoscape!

--Multipart_Tue_Jul__1_16:31:42_1997-1--

--pgp-sign-Multipart_Tue_Jul__1_16:31:42_1997-1
Content-Type: application/pgp-signature
Content-Transfer-Encoding: 7bit

-----BEGIN PGP MESSAGE-----
Version: 2.6.2

iQCVAwUBM7mTYhqJqDLErwMxAQHJOwP/QsJdT3xHzAtqk35VVbBbaPCS1hcE8+lw
Y5VNro/buFwZBfn1vUZ014W7HWavmmFEREip/OLuU6gYTAns7xuracv6CAScbXdi
qpKIOeTdq786hMMKeYiB0/CcXPPC3D1zTKsf+NotF8SjjkjpmW7DTdoq1wUnaqYO
6M1sP4b5OH4=
=CkON
-----END PGP MESSAGE-----

--pgp-sign-Multipart_Tue_Jul__1_16:31:42_1997-1--