To my mind, this is far more effective than FP flash. And you are not wasting flash energy on a series of pulses, either. So, you can get high-speed flash with any flash. Which, as it happens, is totally golden for us. Beyond that speed, the computer just grabs a progressively smaller slice of time from the CCD and "fakes" higher shutter speeds electronically. This helps to protect the CCD from dust and damage. "Electronic shutters also have auxilliary mechanical shutters that actually open and close up to, say, 1/125th of a second. This arrangement first appeared on the D1 and provides one very useful side effect: flash sync speeds are increased substantially (arbitrarily limited to 1/500 on the D50, just like the D1 and D70 series)"
"All shutter speeds up to 1/90 are handled mechanically on the D50, all faster shutter speeds are handled electronically (e.g., the shutter opens for 1/90 and the sensor turns on and off to create the shutter speed effect). Its a bit counter-intuitive that you need a longer flash duration to use a higher shutter speed, but its true. You can read about it in Thom Hogan's site: Some Nikons (D70, D50 and some others) use an hybrid shutter, where the mechanical shutter maximum speed is 1/90 and faster speeds are achieved by the sensor, and that why you get 1/4000 flash sync with any non dedicated flash unit. This became obvious as the image got darker as the shutter time got shorter. The studio strobes actually have a fairly long duration, compared to the electronic flashes you normally find. Turn that off, or use a flash that can't do that)
(careful though, modern SLR flash system often have something called "high-speed sync", where the flash will actually flash multiple times in short succession. You'll only get part of the frame exposed properly. You can try this by setting the shutter speed to something shorter than the sync time and using a flash. This is why SLRs have a flash sync speed, usually 1/125 or /250 or so: That is the shortest exposure time where it will still expose the entire frame. The shorter the shutter time, the thinner that line. There is then no moment that the entire frame is exposed, just a thin line that slides across it. Curtain shutters, such as in SLRs, reach their fast shutter speeds by sliding both curtains across the film plane at the same time.
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