Re: Changing the rom size ?

[markus@infoscape.com]

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Arne Bernin writes:
 > I just want to know if there is a way to build an image.rom-file in the
 > size, I want to have it. If the image netboot builds is 16KB big, how can I
 > get it in 32 KB or even 64 KB. Is there a place in a Makefile, where I can
 > define the Eprom size ?

You do not really have to change the size of the image. There are two
situations, where you might use EPROMs that are bigger than the image:

 - you bought a 27256 or 27512 EPROM (having a size of 32kB or 64kB
   respectively) and you jumpered your network card to map the entire
   space into memory. In this case, you just burn the 16kB image into
   the lower part of the EPROM and pad the rest of the file with 0xFF
   bytes (or some other arbitrary value).

 - you bought a 27256 or 27512 EPROM, but your card only supports
   smaller EPROMs, or you decided to deliberately jumper it to a
   smaller EPROM size. In this case, you concatenate several copies of
   the image file so that you end up with a new image file that has
   the same size as your EPROM chip. This will work, because all 27xxx
   28pin EPROMs are pin compatible. By copying the image multiple
   times, you make sure that the computer always retrieves the same
   data, regardless of whether the extra adress bits are pulled high
   or low.

In general, it is a good idea to map as little memory as
neccessary. This allows more space for other extension cards and
leaves room for use by DOS. That is, why you should consider using
compressed images. Everything that I wrote about 16kB images also
holds true for 8kB and 32kB images.


Markus


P.S.: This seems to have evolved into a frequently asked question,
      maybe it should be put up on the WWW page(s) and/or included in
      the documentation files.

--
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!

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