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Re: 32 kB ROM on 3c509b


On Thu, 25 Sep 2003 03:31:22 +0200, Florian Zumbiehl wrote:
> when trying to use a 32 kB ROM on a 3com 509b I noticed that only 16 kB of
> the ROM were accessible. A bit of research showed that the ROM on these
> cards is paged in 16 k chunks.
> Do you think that it is (easily) possible to change netboot so that it can
> be used with such a paged ROM?

Of course this is possible. I also do have the documentation for the
3C509B, and actually this page switching already works for older
3C905B (which do have a bug which requires switching) and also for
Intel cards with a 595 chipset (which can only access 8kB in one
chunk). It is fairly easy to implement a flash routine into makerom
which allows page-switching (the 3C509B allows using Flash EPROMs - for
normal EPROMs there is currently no provision for supporting page
switching). All necessary functions are already there, so it's just
a matter of calling a couple of subroutines. However, I don't have
the necessary hardware to test it, so it never got into the distri-
bution. I do have a 3C509B, but unfortunately it lacks a ROM socket.


Gero Kuhlmann             Tollenbrink 18      Groote Gracht 33       30659 Hannover      26723 Emden                        04921/997561

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