Firstly it's important to know why sync speed exists, basically when you use a shutter speed faster than the nominal "sync speed" the shutter starts to close at the bottom before it's fully open at the top. Thus at no single instant in time is the shutter fully open so if you fire a flash part of the image will be dark. For most DSLRs this speed is 1/250s.
There are a couple of ways to exceed the 1/250s with flash. You can make the shutter move faster so it exposes the whole frame at once even at high speeds, or you can use electronics shutter to turn the sensor on and off simulating an infinitely fast mechanical shutter.
I think whoever mentioned fast sync with old DSLRs was referring to electronic shutters, as these are no longer used on DSLRs (but are still found on compacts). Reasons for the demise of electronic shutters on DSLRs are varied and there's little consensus though issues with image quality and consistency are often cited.
Even if you're using a mechanical shutter you can sneak past the manufacturer stated sync speed by timing the flash very carefully. The "Hyper sync" function on new Pocket Wizards allows you to tune the flash delay for this purpose.
Here's a summary of the methods and speeds you can expect in practice:
- Fast focal plane shutter (available on some film SLRs) 1/350s
- Focal plane shutter + careful timing (with pocketwizards) 1/400s
- Leaf shutters (found in some medium and large format lenses) 1/800
- Electronic shutters (found in older mostly Nikon DSLRs) 1/1000s*
*Technically you can sync at any speed with an electronic shutter, however past 1/1000 the shutter duration is usually shorter than the flash duration so you start to lose power which halts your ability to overpower ambient.
The only models of DSLR I'm aware of with electronic shutters are:
- Nikon D1
- Nikon D1X
- Nikon D1H
- Nikon D70
- Nikon D70s
- Nikon D50
- Nikon D40
- Canon 1D
I'm sure someone here can fill any blanks from the other major manufacturers. It seems the only model from Canon with an electronic shutter is the original 1D, which is an ancient beast, though the newer 1D models can sync above 1/250s with mechanical shutters.
So in summary there are cameras with faster mechanical shutters / leaf shutters that can beat 1/250s but not by much. If you want crazy sync speeds electronic shutter is the way to go.