Modbus Address mapping vs Manually specifying address registers at the OPC Path

Ignition
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I have a device (MOXA Gateway) from which I’m subscribing to some tags. Due to non-software issues (long cable lengths, interference etc. - let’s say they won’t be fixed) the device doesn’t respond to all requests and I have an overload factor >> 100% when I scan all tags at 3s rate. I changed some tags to 5seconds scan rate and others to 10secs and that helped bring the OF down. Increasing the Concurrent connections to 2 also helped.
However, some tags still report bad quality in some scans.

So I tried address mapping and that reduced the overload factor much more. So I’m wondering if address mapping is better for performance ?

The registers are quite spread out some requiring conversions to int32, some to float, some to unsigned int.

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No, addressing mapping doesn't change performance at all.

If you're actually seeing any performance difference something else changed - how many tags, how many requests, whether they get grouped, etc...

Maybe you can look at Wireshark captures to figure it out.

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Is this related to Span Gaps?

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Not exactly. I had span gaps turned off in both methods.
On that note, enabling span gaps reduces the number of requests and the OF but there are too many bad tags.