Unfortunately, the only advice I can offer is to contact support@ironcladgames.com and talk to them about sending in sync logs. I personally know they want to get rid of the desync bugs, but they are very hard to track - so they should be very, very interested in yours because you desync every time. They should be able to tell you what to change in your user.setting so it spits out the logs the way they need them (there is a simple setting to output a log, but there are also others for checksum tick frequencies that I think they needed changed as well at one point).

Either way, talk to them and be sure to mention that your desyncs are 100% and see if they want the logs. They'll need them from you and all your friends you play with. Also mention if you're running the Entrenchment beta (which also has some sync bugs) or 1.12. A bunch of Entrenchment stuff got reported as well, I'm not sure what their progress is.

Let me know if they don't get back to you in a reasonable amount of time (1-2 days). They're pretty busy with all the Entrenchment stuff going on since they were off for the holidays, but there's an emergency button I might be able to push if you don't hear anything.

Alright, I got an update from Blair:

They found one definite sync bug, but they still need logs. These are the settings you need to have in your user.setting file:

CalculateCheckSumTickFrequency 50
CalculateCheckSumDetail 3
SaveCheckSumSnapShotsInGameTickFrequency 0
SaveCheckSumSnapShotsOnSave TRUE
IsCheckSumLoggingOn FALSE

You should then play the game and when a desync happens, *all* players grab the logs out of the Checksum folder and send them in to support@ironcladgames.com

They still need to check the logs to see if it's the same bug they caught or a new one. It's very important that everyone in the game sends in the logs, not just the desynched player.

Try disabling Alloy for Multiplayer. It seems to be causing all the starbase issues and as far as I know they work normally with it off.

Yes, and the next time it happens both of you should email the desynched game log to IC's support addy so they can inspect them. I forget now, the message you get does show you where it saved the log, no?

Two sync bugs have been fixed since the last reply of this thread. One I believe is in Sins 1.13/Entrenchment 2.5 and another was nabbed just this weekend and will be in an upcoming patch.

Well, the new one that was found sounds like it could actually take care of at least a big portion of the still-existing ones. You can check out Blair's latest dev blog that describes it, but in a nutshell: abilities also have "firing points" and there was a problem in the code that could make things go out of sync for abilities that have more than one (for example Marza's Missile Barrage randomly picks which missile racks to fire from with each missile). So two computers could pick different random firing points, but these are then used in other damage calculations and such so there's the potential to desync if the same firing points weren't picked.

He describes it better of course, so if you're curious take a peek

As far as I'm aware, it would affect both unfortunately.

Well what I find compelling is the fact that the OP is having the same problem also running on a Mac.  If it were as simple as poor use of a random number generator (from a code perspective) this behavior would likely be seen by many, many people playing multiplayer.

My guess is that they are seeding the random number generators in the same way, as to elicit the same sequence of random numbers on each client.  Going out on a limb here, but I wonder if its not due to some difference in behavior of the pseudo-random number generation algorithm on apple hardware.  Would have to dig through their code to be sure.  By the way, the developer blog - I haven't been able to find it - may have already shed some light on the type of bugs they've found/fixed.

Actually, the issue IS the poor use of random number generators - the issue is due to having TWO random number generators - a deterministic one and a non-deterministic one. The bugs come from using the non-deterministric one for something that must be in sync on all computers. The reason this is not more prevalent is that the more common times where a mistake was made and the wrong one was used have been fixed, so its the very rare ones that are hard to track down that are still in the mix...

Strange, because I've only had positive experiance with them -- and most people would agree!  What problem are you having with them?

Don't feed the troll, guys.

I'm not sure if this will help but my brother and I have been playing with pretty close to the exact same hardware (two iMacs and a MacBook Pro running Win XP on Boot Camp) and we still get the sync error every time.  I understand that the Laptop is going to have a different chipset but I would think it should still handle everything the same.  Are you saying that it's guaranteed that we will have issues as we are not using "standard PC" hardware?

Also, it seems to me that something must have changed with an update because we used to be able to play games without loosing sync.  Granted, we updated because the game would crash after a couple hours but at least we weren't wasting our time thinking we were still playing together.