Basically, I don't wish to be forced to use Dell-laptops with serial ports in my work and want to know someting about this hardware interrupt the serial ports can generate and the most likely port a mac has that can do the same job, wich I think is Thunderbolt, see ScoobyMcDoo's post. But as I said, this is another discussion, one I have to have with some hydrographers sometime.
Unless you're planning to write a device-driver that interfaces to Thunderbolt, I don't see how Thunderbolt is relevant, even if it did have a hardware interrupt.
If you are planning to write a device-driver, you will need to know an awful lot about low-level kernel details, programming languages, and time-critical scheduling. Even then, the likelihood that a Thunderbolt interrupt will work just like an old-style serial-port interrupt is virtually nil.
If you already know all that for the Mac OS X kernel, then good. I suspect, however, that you don't, otherwise it's unlikely you'd have asked about a Thunderbolt interrupt at all. I think you picked "hardware interrupt" as some kind of misguided requirement, without actually understanding everything else that servicing an interrupt entails.
And if you're planning to write a device-driver, that's not likely to be something hydrographers can answer questions about. They might be able to tell you what kind of computers they buy, but I doubt that many of them write device-drivers.
Assuming you had a clear definition of what's really required at the hardware level (and I honestly doubt that, given what you've posted so far), the most sensible thing would be to remove Thunderbolt or any other Mac-based interrupt entirely.
Instead, program an external microcontroller to collect both the GPS serial message and whatever time-critical measurement is being delivered (you haven't said what that measurement is, nor how it's provided). Even something like an Arduino Uno might be able to do that, without a huge amount of programming. If it's really time-critical into the microseconds range, then you'll end up using something like a timer input-capture and possibly writing code in C rather than Arduino's unique brand of C++. The results collected by the microcontroller could then be sent to the Mac (or any other computer) over USB or any other relevant interface, without the need for time-critical drivers in the host computer.
FWIW, I'm currently working on a hardware project using an Arduino Mega for prototyping, that involves precision timing, microSD storage, and wifi communication, so I'm not just talking hypotheticals here.
EDIT
It's quite possible that your only choice is to buy a computer with a classical serial port that uses hardware interrupts. The software that runs on the computer may require those components, and there is no alternative.
Since you haven't said anything about the software, that's just a guess, but it wouldn't be the first time that some task-specific software needed specific PC hardware in order to run.
If the software does need a serial port with classical hardware interrupt, then you and your fellow hydrographers won't be able to buy any of the newer Ultrabook models, either, which lack a classical serial-port. And some other sub-compacts or netbooks might also be unusable. That's just the way it goes with task-specific software sometimes.
