Communicationl buffer overflow error

[Danny Boy]

I am getting communication buffer overflow errors (Error #69) on a Compaq
laptop running XP Home Edition. I connect a digital ocilliscope through the
serial port and use software supplied by the manufacturer. The software is
written in Basic and returns an Error 69 when using anything over 4800 baud.
It works fine at 4800 baud but crashes at any speed above that. I have tried
myriad combination of FIFO buffer setting and flow control, but nothing
seems to work. This all worked fine on an old 386 Compaq but the problems
started when we moved the system to a new PII Compaq laptop.

TIA

 

[Guest]

It sounds like the oscilloscope software can not keep up with the incoming
data rate on the PII running XP. You probably do not have enough memory on
the PII to run XP properly. XP requires a LOT of memory.

Right click on the task bar at the bottom in an empty space and click on
Task Manager. Click on the Performance tab. Compare the Total Physical
Memory with Commit Charge. If Commit is larger than Physical then you are
running in virtual memory and may not be able to keep up.

You should have 256 meg memory at a minimum and 512 meg is better for you
type of application.

It probably ran fine on the 386 because Win 95 uses less memory and gives
more latitude to programs.

 

[Danny Boy]

Thanks for the reply,

I checked the Task Manager, as follows:

Physical Memory: Total - 457K; Available - 241K
Commit Charge: Total - 150K, Limit 1080K, Peak 165K

Also, the new Compaq has an AMD Athlon processor, not PII, my bad. The
oscilliscope software is a DOS based app that I run full screen with no
other apps running (other than all the normal Windows overhead).

I would love to get this thing speeded up. A 4000 data point transfer at
4800 baud is a real drag.....

 

[Alex Nichol]

I checked the Task Manager, as follows:

Physical Memory: Total - 457K; Available - 241K
Commit Charge: Total - 150K, Limit 1080K, Peak 165K

Also, the new Compaq has an AMD Athlon processor, not PII, my bad. The
oscilliscope software is a DOS based app that I run full screen with no
other apps running (other than all the normal Windows overhead).

You have plenty of Memory around; the trouble lies in the buffer built
into the software you are using, and it sounds as if things are just not
fast enough to get that under control. Access via COM ports is liable
to be a very CPU intensive matter, And a DOS app is running not via
true DOS interrupts and servicing, but in a 32 bit emulator, which is
more CPU intensive still. A thing you could try is to look for the
Process in Task Manager, right click, Priorities and set a higher one -
even up to Real Time. But I don't hold out much hope: you really need
a proper 32 bit capture program, or else set up to dual boot to a true
DOS
..

 

[Danny Boy]

Thanks for the reply. I kind if suspected it was more an issue with the
capture software, but it did run OK under Win98. My next thought was to set
up a dual boot to DOS, so I guess that's confirmation. Is there any
advantage to installing Win98 vs. DOS? I think I have DOS 5.0 and 6.2 laying
around here somewhere.