USB-232 has hyperthreading support?

[menchar]

I have a couple of questions in re the NI USB / rs-232 converters.

Is there a performance advantage Vs. a PCI-8430?  While the 8430 claims hyper-threading and multi-processor support, I don't see the same claim made for the USB / rs-232 converters.  Other than conservation of PCI slots, why would you want to use a USB / rs-232 converter?  Especially a USB 1.1 device (Vs. USB 2.0).  Plus, now I have a box dangling from the PC.  We've had trouble with non-NI USB / rs-232 converters on hyperthreading PC's.

How can the USB / rs-232 converter provide null modem capability for devices that need it?  How can it automatically figure out that a connected device needs, for example, CTS or RTS or DSR or DTR or DCD asserted?  A "null modem" cable often doesn't simply swap TD and RD.  There's no such thing as a "standard" null modem cable that I know of - there are any number of variations.   Does the USB/rs-232 swap around the sense of the other rs-232 lines as well as RD and TD?

And what about using a 25 pin Vs. a 9 pin connector on the device - does the USB/rs-232 converter somehow know the difference?  You'd have to have a patch cable anyway if you're going to a 25 pin connector.

Thanks,

Bob

[MissyS]

Hi,

The entire NI-Serial driver is symmetric multi-processor (SMP) safe. Since the NI-Serial driver leverages multiple threads to perform operations we do see a increase in performance on multiprocess or hyperthreaded machines. We do rigerous testing on multiple hyperthreaded processor systems. Since the USB-RS232 uses this driver, hyperthreading is supported on the USB-RS232 as well.

An advantage of a USB-RS232 device is portability. Like you said, it is good for conserving PCI slots and for computers that do not have PCI slots, like laptops.

You can configure the type of hardware handshaking or flow control in your VISA serial configuration or by property nodes. This can also be done in Measurement & Automation Explorer.

Using either the 25 or 9 pin connectors will not change your configuration because the lines will be wired into the correct pins on the serial port. There will be no difference to the serial port.

Regards,

[menchar]

Miss Missy-

Thanks for the info, I appreciate it.

While the serial driver may be thread-safe, there seems to be a deeper issue in re hyperthreading.  

Why does NI specifically claim hyperthreading support only for the PCI 843x cards?   

We've had to disable hyperthreading on a multi-processor PC with WindowsXP in order to get ordinary com ports to work on an app built with CVI 7.1.

"Hardware" flow control almost always means the CTS / RTS lines.  DCD, DSR, DTR often must be asserted (or not) in order for a device to work.  I don't see that the USB/rs-232 converter can automagically figure this out.  How can it anticipate what type of null-modem functions might be implemented in a cable?   I can see where it can figure out where RD and TD and maybe signal common are pin-wise - and then figure out if the connected device is DTE or DCE - and then anticipate where the rs-232 functions are on the other pins, but I still don't see how it could work with just any cable.

Thanks, Missy, for you help.

Bob

[Dennis_Knutson]

I've not worked with NI's PCI serial boards but I have worked with several other PCI and USB->Serial devices and none of them will automatically detect anything. You can write a program to detect baud rate, handshaking, etc. but the program would probably have to be pretty specific to the instrument you're trying to connect to. Auto-switching between DTE and DCE is something I've not heard of either. I have a couple fo expensive test instruments that enable to do that switching but it is something I have to command and not something the instrument will do on itself. Just like when you use Hyperterminal, the com settings is something you usually have to know in advance and the cable type is something that has to be selected to mathc the type of instrument you are connecting to. The typical serial board does not have any capability to switch the TX and RX pins.