User manual

Appendix
ComTec GmbH 7-11
7.6. Frequently Asked Questions
7.6.1. MPA-3 Performance
Q: About the 4K and 16K FIFO: Can you give me some firm ideas on how to recommend to customers
which they need? Is it based on a count rate issue; i.e. up to some count rate the basic 4K FIFO is ok,
then above that the customer should order the 16K. I need to offer some logical explanation on how to
select these options.
A: Please look in our web-page what we have about the MPA-3 system. Under "Performance" a pdf file
can be downloaded describing the throughput that can be achieved using a single- and dualprocessor
system with the three possible FIFO sizes. The essential numbers are contained in the following table:
ADC Conversions/sec without loss of data
single Pentium II 350 MHz Dual Processor
4k FIFO (standard)
with display
w/o display
590.000
2.526.000
3.730.000
3.905.000
16k FIFO (option)
with display
w/o display
1.092.000
3.570.000
3.800.000
4.000.000
List data to SCSI 1.600.000 1.600.000
List data to IDE (DMA mode
enabled in registry)
800.000 800.000
Q: How can the DMA mode for my IDE harddisk be enabled in the registry?
A: Windows 98 and 2000 should DMA mode enable automatically. But under Windows NT it is necessary
to have at least Service Pack 4 and to change some registry entries. Check the registry by running
regedit and look under HKEY_LOCAL_MACHINE...HARDWARE...DEVICEMAP...Scsi...Scsi Port 0. If you
see for the DWORD value DMAEnabled the value 0x0, DMA is not enabled. If you see a value 0x1, it is
already enabled. To enable it, look under
HKEY_LOCAL_MACHINE...SYSTEM...CurrentControlSet...Services...atapi
and add here a key named Parameters and under Parameters a key named Device0. Then add here a
new String Value named DriverParameter and set its value to "DMADetectionLevel=0x1". Then reboot the
system and look whether DMAEnabled is now 0x1. If it is still zero, you have probably an old BIOS,
motherboard, or harddisk. Without DMA mode enabled, the typical maximum value for ADC conversions
per sec and writng a listfile to IDE harddisk is only 120.000 instead of 800.000.
Q: MPA-3 Performance Chart: When I look at the performance chart in careful detail, I have several
questions: A. Exactly how much is the throughput affected by fewer parameters. For example, most of our
applications involve 2, 3, or 4 parameters only.
A: If you have 4 ADCs instead of 16, you can in principle use a throughput per ADC by a factor of 4
higher before you see a count rate limit.
Q: B. Exactly what does he mean by "ADC Conversions/sec without loss of data"?
A: At this measurement we observed the FIFO full flag with a scope at the PCI board to explore the limit
of the throughput without loss. Above this limit still even more data per time are taken, but with some loss.
Q: Clearly, the ADC's are NOT included in this measurement, right? So what is ADC "conversions"? I
thought it simply means the number of digital data words that the MPA-3 could accept per second