I wrote all the Icarus timing code in cgminer and all the code that adjusts it (and redesigned all of that in the Icarus code)
So yeah the following is correct
The current code defaults to 11.2 seconds (not 11.3s) before aborting the work and starting again
It gives a little lea way of 1 unit of time (1/10sec) in case there are any processing delays
However, 11.2s is calculated based on the Icarus mining at 2.6316ns per hash
(which of course means 5.2632ns per pair of hashes)
i.e. (2^32 * 2.6316 * 10^-9) - 0.1 = 11.20...
What it will also mean is: if you are hashing faster, and complete the nonce range without finding a valid nonce before 11.2s, then the icarus will be idle for "11.2 - however long it takes to complete the nonce range" each time that happens.
So the correct value in place of 2.6316ns, will ensure it isn't ever completing and waiting for new work.
It would only have to be 1% faster to end up waiting.
The second thing that the correct nanosecond value does, is help cgminer to calculate the correct MH/s value.
With the correct value, it knows how many hashes it has done when it aborts the work (at 11.2s in the current settings)
If it doesn't have the correct nanosecond value, it will report the MH/s incorrectly (hi or low depending on the speed of the bitstream)
The option: --icarus-timing short (or long) tells the code to work out the correct values and use them.
N.B. you will get a message on the screen each time it re-estimates the values, like:
Icarus %d Re-estimate: Hs=%e W=%e read_count=%d fullnonce=%.3fs
The first %d is just the Icarus ID number
The Hs=%e is the hash nanosecond time it has calculated (in place of 2.6316 * 10^-9)
The W=%e is the code overhead per work
The read_count=%d is the new replacement value for 11.2 (times ten)
The fullnonce=%.3fs is how long it actually takes to complete a full nonce range
You can also ask the API for the current values it is using:
java API stats
Once you have a new correct nanosecond value for your faster bitstream (lets say it was 2.2222ns), you simply start cgminer with the option:
Of course if you have any trouble with this, come visit FreeNode IRC #cgminer - I'm almost always logged into it as 'kanoi' (but not always available to help but I will see the messages later if I'm asleep or elsewhere)