Mail Archives: opendos/1997/03/11/11:07:19
Hi!
On Mon, 10th Mar 1997 17:53, Jon Visick asked many questions:
I hope, I can answer some of them...
> How does Opendos multitasking compare to DESQview?
Since I don't run DESQview (unfortuately, it's *very* rare here),
I can't give you a direct comparison.
Here are some facts: NWDOS/OpenDOS multitasking is preemptive,
not cooperative, as both Windows 3.xx/95 are. Since DESQview runs
on XTs also, DESQView's multitasking should also be only cooperative.
Maybe this has changed with newer version of QEMM and/or DESQView/X???
(Some DV experts in the list???) So, in theory, NWDOS/OpenDOS
multitasking kernel is very sophisticated (it emulates a Windows
kernel in some respects), in practice there is still a lot to do at
the user level to make it convenient as DESQView.
> Is there cut and paste?
Currently not. There had been cut+paste with DR DOS 6.0 TASKMAX as
a task switcher, but this has been stripped off from Novell's TASKMGR
for unknown reasons. Looking at Caldera's multitasker docs, it
should not be a big problem, to reintroduce these functions, since
the kernel offers a wide range of queues, that can be used for such
purposes.
> Support for graphical applications and high-resolution screen
> modes?
Yes, if you use standard VGA resolutions. You can use the full
capabilities of your video hardware, if you use only one graphical
application at a time, do not switch the foreground application,
and don't backfill video memory address space (MEMMAX +v). Note,
that there is only one foreground application, not a windowing
system, and depending on your applications, you may need to set
ClearScreen= option in the TASKMGR.INI file. In practice, there are
some problems, since the current implementation only virtualizes a
standard VGA. Monitor switching on dual monitor systems (e.g.
HGC+VGA), and several non-standard high text modes are not supported
and may lead to strange results. It should be possible to write VxD
drivers to improve virtualization of better hardware in the future.
> How big is the memory "footprint" when multitasking?
This depends on the programs loaded before you start TASKMGR,
since each task (called domain in Caldera's docs) has shared
and instanced memory regions. You should calculate 1MB/task
(as for Windows 3.xx).
The real-mode stub of the multitasking TASKMGR is ca. 5KB-8KB.
> Does the multitasking system recognize "DESQview-aware"
> applications written to give up their time slice?
It uses several standard methods to communicate with idle
applications. Special DESQview API's are not supported.
For details, have a look at the multitasker docs from Caldera UK.
> Does it allow for controlling applications which do not give up
> their time slice on their own?
Yes, it's preemptive multitasking! That's one of the major advantages
compared to Windows 3.xx/95.
> How customizable is the multitasking system: can you specify
> conventional and extended/expanded memory limits for each program,
> for example?
Yes and no. This depends on starting TASKMGR as a multitasker or
task switcher. Have a look at the TASKMGR.INI settings. On API
level, you can better fine tune the system, but currently, there
are no user level tools to do this on a application by application
basis...
> (2) Is Opendos compatible with QEMM?
Yes, I think since 7.01+...
> Or does it have built-in memory management of similar quality?
Yes, NWDOS/OpenDOS EMM386 does not provide Squeeze and Stealth
options, but in many configurations, you can force EMM386 to do
very similar things manually. Some people reported problems with
QEMM, where EMM386 worked ok for them, some reported it vice versa.
Note, that DESQVIEW/X needs QEMM, and cannot run with EMM386, while
DESQView will run with EMM386, but cannot use advanced multitasking
capabilities.
> I'd be hard pressed to give up the
> significant amount of driver space in upper memory provided by QEMM's
> Stealth technology, not to mention the 637K of available conventional that
> can be had with QEMM's ability to move files, buffers and most of DOS and
> 4dos to upper memory.
Using some tricks, you can get this (and even more) with EMM386,
too. NWDOS/OpenDOS' EMM386 is very sophisticated compared to poor
MS-DOS/PC-DOS. NWDOS/OpenDOS does not load high FILES and FCBS, but
you can use QEMM tools instead. They run fine with EMM386. Have a
look at my NWDOSTIP.TXT file (from MPDOSTIP.ZIP) for details on how
to get the most out of the memory managers and fine tune your system.
Bye,
Matthias
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