NI5112/5122 digitizers performances in a pxi system

[Roberto_N.]

I�ve to configure a PXI based signal processing system, composed of:
-PXI chassis + 8186 Controller,
-N.2 NI5112 8-bit digitizers (or N.2 NI5122 14-bit digitzers).

I want to configure a four channels acquisition system, performing a continuous data acquisition in Labview environment, and I need of some confirmations about transfer rate limitations.

I�d like to know the theoretical maximum (continuous) transfer rate between the four channels and the controller (with 8-bit 5112 configuration or with 14-bit 5122 one).
For simplicity we can think that without data storage and processing.

I know that the PXI bus performs a rate of 133 Mbytes/sec, so in a configuration of N.4 acquisition channels, we obtain 133/
4 = 33 Mbytes/sec for every channel.
This is simply 33 Msample/sec in a 8-bit NI5112 configuration, while becomes 33/2 = 16.5 Msample/sec in a 14-bit NI5122 one.

Is that right?
Are there other bottle necks (related to the acquisition cards or to the controller)?
Thank you in advance.

[Luigi_B.]

Hi

yes your calculation is right even if these are pure theoretical values becouse they would depend on your PC performance and other data traffic present on the PCI bus due to other boards (like video, ethernet etc.).
Between the two options the 5122 will be better for a longer time frame acquisition due to the higher onboard memory that will offer a maximum of 256MByte/Ch instead of 32MByte/Ch (128Msample 14 bit/Ch vs 32Msample 8 bit/Ch) and also for the SMC architecture that will offer advanced timing & synchronization features even if the higher resolution (14bits) will decrease the potential transfer rate in a continuos acquisition.
If you want to learn more about the SMC architecture and its advantages you can look the link here attached.

http://zone.
ni.com/devzone/conceptd.nsf/webmain/63CA1E64DA2AAA3486256DE90003F124?opendocument

Hope this help
Luigi