Hello David!
14 Mar 97 21:28, David Noon wrote to James Mckenzie:
 DN> Hi James,
 DN> Since you roused my curiosity, I decided to write a little test
 DN> program that would access 40MB of DPMI storage. It worked perfectly,
 DN> allocating and _committing_ all 40MB without incident beyond bloating
 DN> the swap file a bit.
Did you use the DOS/4GW executeable to do this?
 DN> I still don't understand this. DPMI is memory, not file.
DOS/4GW allows the DOS environment to access more than the normally available 
640KB for executeable and data files.  The earlier versions (<1.94) used a 
method that was not compatible with OS/2's VDM structure.  The later versions 
started to use DPMI, but were limited to 32MB of combined executeable and 
data file in memory.
 JM>  DN>> The limit should be determined by the DPMI server, not the
 JM>  DN>> client. In a VDM the server should be OS/2's VMM, not
 JM>  DN>> DOS/4GW.
 JM>>
 JM>> You are correct according to the way things SHOULD work,
 JM>> but remember, DOS/4GW was written to run under pure DOS, not an
 JM>> OS/2 VDM.
 DN> A DPMI client is obliged to obey the DPMI conventions. These are not
 DN> dependent on pure DOS. Indeed, using DPMI makes DOS very impure, since
 DN> a DPMI server switches the CPU from real mode to protected mode.
True, David.  However, the interface presented by DOS/4GW is not which a 
"true" DPMI interface would present.  It has its limitations.  BTW, this all 
come from the version I received with Watcom 10.0. (1.97?)
 DN> The DPMI server should provide the standard interface too. The VMM in
 DN> an OS/2 VDM does precisely this. So does DOS/4GW server, when it is
 DN> active. It isn't active in a VDM. Only the client code from DOS/4GW is
 DN> active in a VDM.
Again, true.  But DOS/4GW is designed to setup its own DPMI environmet. 
Remember, DOS does not setup DPMI like OS/2 and several other OS's do.
However, OS/2 can provide up to 512MB of DPMI space.  The limitation is not 
on OS/2, but rather the DOS/4GW stub that was provided with Watcom.  DOS/4GW 
Professional can access up to and including all of the space that OS/2 can 
provide.  However, I think at that point it would be better to have a native 
OS/2 version of the executible.
James
... Computers are irrelevant- Windows has been assimilated.
--- GoldED/2 2.50+
(1:309/63)
---------------