RE: DiVa data collection issue

Hello Ryan,

with regards to the DiVa collection issue, we also observe this problem on our LSRII system. I have added two screenshots from measuring the same 8 peak bead sample, the problem is clearly recognizable when lots of plots are opened (the "busy" worksheet vs. the "light" worksheet). 

In our hands, the problem always occurs when the CPU usage of the HP xw 4300 workstation goes up to 100%. Therefore, as a workaround, we watch the CPU usage via the XP task manager and make sure that it is well below 100% by avoiding to open too many workspace items.

Kind regards,
Steffen


Dr. Steffen Walter
Director T-Cell Analytics
Direct: +49 (0) 7071 565 125 40

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-----Ursprüngliche Nachricht-----
Von: Ryan Duggan [mailto:rduggan@bsd.uchicago.edu] 
Gesendet: Mittwoch, 30. April 2008 17:09
An: Cytometry Mailing List
Betreff: DiVa data collection issue


We've noticed a strange, but substantial quirk on our DiVa systems  
that we're wondering if others could corroborate.

The symptom presented itself as a large discrepancy in the number of  
Threshold events (# of events recognized by the instrument) versus the	
number of events Processed (# of events that actually get processed  
and saved in your file).  More specifically, the more events you  
collected (Threshold) the fewer events were actually saved  
(Processed).  Typically, the reason this occurs is because of  
coincidence aborts.  Since there is no dead time on DiVa instruments,  
the abort rate is usually only about 1%, assuming you have your window	
extension set properly.  But, what we were seeing is that the  
processed event count 'plus' the abort count, which should be nearly  
equal to the threshold count, was way off, as much as 50% of the  
threshold count.  After messing around for a while, the bottleneck  
ended up being the number of 'objects' being displayed on the  
worksheet.  I'm using the term objects to refer to either a dot within	
a dot plot, a region, or simply a plot itself.	The more of any of  
those object that the graphics card must process, the fewer the events	
it can process, therefore leading to a lot of data loss.  It should  
follow then that if you display fewer objects, the data loss will  
decrease, and that's exactly what happened.

We did one or two of the following to fix the problem:	1.  Close all  
but a couple of dot plots in the worksheet to monitor integrity of  
data.  2.  Change the "Events to Display" menu to a small number, e.g.	
5000 events.  3.  Do both.  As soon as this was done, Processed events	
was right back to "normal" levels.

This turns out to be a huge impact on overall yield for sorting as  
well because if it doesn't get processed, it doesn't get sorted.  I  
suspect this is the reason why we've typically seen better yield on  
our MoFlo than we do on our Aria.

I already knew that the sub par graphics card on these HPs caused the  
displaying of plots to lag after you collected your large files, but i	
didn't realize it was a bottleneck for data collection.  Has anyone  
gone ahead and installed a high powered, really fast, graphics card in	
there standard HP to improve this issue?  Can you send me info on what	
one(s) you've used?  I'm using an HP XW4400s, and have noticed this on	
an Aria and LSRII.  Do you think it's something other than the	
graphics processor?

Thanks,
Ryan


-----------------------------------------------
Ryan Duggan
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Flow Cytometry Facility
University of Chicago

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