I realize this thread is several months old now, and given that Tempest development is officially over, it's not like we're going to see any more fixes; but I wanted to throw my proverbial two cents on the pile here, if only to commiserate with those of you have noticed just how shoddy the Tempest's internal clock can be, and to counter (no pun intended) the "expected behavior" argument.
As some of you know, I've been touring professionally for a long time (28 years and counting in fact), and I often choose to run the various electronic components of my live rig without MIDI sync, because I find it liberating, less rigid, and ultimately more engaging. Hell, sometimes the material simply won't allow for it, and actually requires the tempo be flexible. Sufficed to say, I've done this before. Anyway...
Recently, I've had reason to run the Tempest unsynced (if that's a word) alongside several other sequencers and drum machines, and ya... Bottom line is, the stability of its internal clock is truly deplorable—measurably worse today than it was in the early days of the operating system—so much so that it's basically unusable now when running free against other clock sources.
In the studio last night with a colleague, we had a lot of gear with us, so we decided to run a practical, real-world test:
We manually synced up four Elektron boxes {MachineDrum, Analog Four, Analog RYTM, and an Octatrack} with the Tempest—No MIDI cables involved, just our ears and impeccable rhythmic sensibilities (wink)—and just for shit's and giggles, also hit play on several budget drum machines and groove-boxes as well {Alesis SR-18, Korg Electribe 2, and a lowly Roland SP-404SX}. I kid you not, at 78 BPM the Tempest was already starting to flam against the other boxes just 4 bars in, and didn't make it 8 bars before it was so far out of sync that it had to be stopped and restarted. The other machines, on the other hand, made it nearly 40 minutes before the trough got too wide!
For good measure (again, no pun intended), we slaved the Tempest to the SR-18, and did the test again... We were easily able to jam with the other boxes, unsynced, for 20 - 40 minutes on average without having to reset. Take from that what you will.
So, will "any two devices which are not synchronized eventually drift out of time due to inherent differences in their respective clock stabilities"? Yes, of course. But not like this. The Tempest seems to run almost a 10th of a BPM slow, depending on tempo. That's not acceptable by any standard.
Cheers!