Link to home
Start Free TrialLog in
Avatar of marchant
marchant

asked on

memory and absolute decleration ?

Hi all

ok here go's Im currently accessing a ISA plug in card using memory read and write ... and it works fine ... no problems as long as the card address is in the c9000 range I can get direct comms by declearing a var absolute which works fine so there is no need to write a vxd ... what I want to know is

a: why ? lol

b: why only in that one address range ?
( any other range and the read write lines on the isa buss are not activated
)

and lastly ... there does not seem to be any system memory alocated to this adress ?

thanks stephen :)
Avatar of Madshi
Madshi

Oh well, there are some secrets in win9x. E.g. memory mapped files are always mapped to the same address in each process and so on. Things like that are not documented anywhere, because they might change in a future Windows version.
So if your program relies on the fact, that IO calls work fine at $C9000, you might have bad luck already with Windows Millennium. My only recommendation can therefore be: Choose the safe way and write a vxd  :-(.
If you absolutely don't want to, if you choose to use the undocumented $C9000 way, test your program at least under all variants of win9x, that is win95 (old version), win95osr2, win98, win98SE, winMillennium.

Ehm, sorry, I can't answer your questions directly, hope my comment helps a bit, nevertheless...   :-)

Regards, Madshi.
I have written many VXD's - plain fun - and well, yes if you want be sure you get real direct hardware access on non-NT windows platform's you actually need to write a VXD. That isnt actually a big problem a generic VXD that does expose direct memory access has maybe 10 lines of unique assembly code :) well there are 42+ CD you have to dig first :) well if interested I will be publishing all source code written by me and/or copyrighted to Silicon Studio Inc. this will include maybe 12 VXD's and some Pascal programs that talk to those VXD's.
Hi sistudio, that sounds quite interesting! If you publish those sources, I would love to get a copy, too. I'm not doing any VXD development right now, but who knows what will be in 2 weeks. So having some good VXD examples would be a good starting point then...   :-)

Regards, Madshi.

madshi@gmx.net
ASKER CERTIFIED SOLUTION
Avatar of sistudio041900
sistudio041900

Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
Thank you very much - that's kind!!   :-))
Avatar of marchant

ASKER

thanks sistudio it seems I have to go with the flow and start wriing vxd's

any other pointers would be apriteated
ie any good boks out there ?