PCSIM DMODE V OPERATION ON A REMOTE X SERVER.
ITEM: RTA000023200
Q: Has anything been done in PCSIM to improve the speed and decrease
the network load while running in a VGA mode to a remote X server,
as in:
pcsim -display other:0 -dmode V -refresh xxx
Has any work been done to do "bitmap deltas" or only write the
portion of the screen that has changed? What about reducing the
color map depth?
Or, is it still that if I run in -refresh 20 mode, would the math
still work out this way for network load:
640 * 480 * 8 * 50 (width by height by depth by screen/second =
bytes per second to run PCSIM)
A: It has not changed. Each line- or screen-generating action to the
remote display PCSIM session requires a refresh of the display
matrix (which is minimally the 640x480 you described in 3.2, or
by default, 720x480 pix). The network load is very large. The
developers of PCSIM were sensitive to this, so they made PCSIM
a real memory-only package (to save being paged out when it is
sleeping). This means that the 1.5MB video memory allocation of
PCSIM Release 2 can update the network from real memory. That is
not enough to get you PC-like video performance across the
network.
Your question about writing only the portion of the screen that has
changed (kind of like backing store in X-windows) is a point well
taken, but would require that the Xstation's (or other X server's)
own memory be used. This can't be done because of that video
memory element I described to you above. It's sometimes easy to
forget that we're dealing with a simulator and that what is going
on inside of the window, AIX and X are ignorant about. DOS (which
understands the windows content) is only communicating with the
video memory, and that must be where the simulator is. To off-
load this memory to the remote X server for efficiency would
require enhancing the communication between it and the simulator
executable that may sacrifice the speed it gained. Right now, it
can be done with IPCs and shared memory segments, but if it was
off-loaded, it wouldn't be as efficient.
It's really important for PCSIM users to understand how it is
intended to be used. It was never intended to replace networked
PC's, or establish a multi-user DOS environment, even though it
does provide some features that make multi-user environments possible.
PCSIM was intended to be used by people who need to run DOS programs
infrequently, but want to have quick and easy access to them at
their workstations. It is also considered to be a good tool for
users who want to transition from DOS to UNIX.
In spite of this level setting of expectation, PCSIM is packed with
new features. Here is a brief summary of the features:
1. Monochrome support of Code Page 437 on HFT, aixterm, and async
terminals.
2. VGA support is no longer limited to 720x480. (If you use a 6091,
hit the Motif maximize button on your PCSIM window and you've
got a full screen PCą. It looks great, but is a little slower
to paint.)
3. You can now run either the Microsoft Mouse program or the
IBM PS/2 mouse driver.
4. No change to parallel printer support -- simply define lpt1, 2,
or 3 (no more than 3) to any print queues your system uses, and
DOS will think that they are parallel printers.
5. No change to serial support -- exclusive mode.
6. Expanded Memory, LIM 4.0 and INTEL 80286, HIMEM.SYS (sorry, this
does not include protected mode).
7. INTEL 80287 Math Co-processor support. This allows the
simulator to use the RISC/6000's floating point processor like
a math co-processor. (Some of the initial benchmarks that were
run showed it to even be a little faster.)
8. You don't have to use a "Simulated DOS Partition" anymore. You
may now install DOS to an "Emulated Hard Drive" which is
essentially an AIX directory path. This means that programs may
now be run from the unaltered AIX path, and if permissions are
set properly, multiple users can run the same programs at the
same time. You can limit the simulator to handle the number
of sessions you specify.
9. The above change also means that you can export the file system
that contains DOS data and programs under NFS or AFS. If you
have several RISC/6000 workstations running PCSIM, accessing
the shared data or programs across the network would be much
faster than running PCSIM at a workstation because there is no
need to send the large video image packets across the network.
There is also the capability of using CDROM file systems if they
are properly mounted by AIX, and fall within the directory tree
used by DOS.
CAUTION:
PCSIM is still an 80286 simulator, not an 80386. It does not support
multi-tasking in Windows 3.0. It does not support OS/2. Because
it is a simulator, the machine that DOS uses is simulated, so DOS
can have no real understanding of its configuration. Because of
this, you can't talk to RISC/6000 adapters from DOS -- none of them.
The Simulator still can't be used for applications that are timing
dependent because of the drivers and converters that access the
serial ports it uses.
If your applications directly access fixed disk or diskette
controller hardware, they will not run on the Simulator.
You can't use just any CDROM format that other PC's will accept.
It has to be the format (ISO9660 and High Sierra) used by AIX.
And finally, remember that the performance is being limited by the
video display for the reasons that I described earlier. A lot of
users think the simulator as being slow. In reality, the program
runs quite fast, but the display (video) cannot keep up with the
speed of its processing.
Let me summarize all of this for you:
1. Improvements to speed or VGA-remote network load? No.
2. Can the screen be updated instead of redrawn? No.
3. Has the depth of the video matrix been reduced? No.
4. Does the network overrule changes you make to the refresh
flag? Yes.
5. What's new? See summary of new features above.
---------- ---------- ---------- --------- ---------- ----------
This item was created from library item Q580942 2VQCP
Additional search words:
$$A CHANGES DISPLAY DMODE DSPLY IMPROVEMENTS IX LOAD MAR92
MONOCHROME NETWORK NETWORKING NEW OPERATION PC PCSIM RATE REMOTE
RISCSIM RISCSYSTEM RJE SERVER SIMULATOR SOFTWARE SPEED TP VGA
XSTATION 2VQCP
WWQA: ITEM: RTA000023200 ITEM: RTA000023200
Dated: 01/1996 Category: RISCSIM
This HTML file was generated 99/06/24~12:43:08
Comments or suggestions?
Contact us