MXI-4 Selector Switch?

[Ben999_]

Hi, I'm wondering if anyone has had any experience with using a standard DB9 selector switch (such as the one shown here - http://www.l-com.com/item.aspx?id=3237) to switch between two copper MXI-4 connected systems. The purpose of this is to allow two PC's, each with their own MXI-4 controller cards to access resources in the same PXI chassis without swapping cables. Only one PC would be powered at any time. The selector is a straight-thru connection, so the wiring should not be an issue, but the high speed MXI is a concern since it operates at a much faster rate than RS232 serial. Essentially a weaker, potentially less shielded link would be present in the path from the PC to the PXi chassis for a portion of the cable with this setup. I'm hoping to find out if anyone has tried this and what the results were.

Thanks,

Ben

[Robert__R]

Ben,

I haven't tried this, but I'll comment anyway.  🙂

The impedance of the switch will be way off and may cause trouble with the link.  It's hard to say how bad it will be without testing the switch.  If you have the hardware it shouldn't hurt to try it, though.

MXI-4's error correction is pretty robust, so any data that makes it through will be good.  Depending on how bad the connection is the results could vary from flawless performance to a non-functional setup.  The more interesting cases are in the middle.  When an error is detected, several packets will have to be retransmitted.  If there are many errors this could get to the state where data moves slowly and/or takes a long time to get through (possible timeouts if severe enough).  Packets with errors will experience increased latency, which may or may not matter.  

Of course the results can also vary by day, temperature, or phases of the moon.  You're also increasing the length of the cable, which could have an adverse effect as well.  If you try it I'd be interested to hear how it goes.

- Robert