Ralph,
Here is the information that I was sent:
Salsco 6" hydraulic feed wood chippers all have extra wide openings so that you don't have to do any trimming. The Model 826PTO is hydraulic feed, 6" high x 12" wide opening at the infeed. This unit does not require hydraulic oil from your tractor, it is fully self contained, and sells for $8124.00.
The Model 627XT is the hydraulic feed version of the Model 627. It is a dual feed unit, with flow control to control the infeed rate. It will require oil from your tractor, and it sells for $5374.00.
Speed Sensing, which monitors the RPM of the Impeller, is available as an option for both units. $763.00.
If you are planning on chipping 6" round wood continually, and maybe even going a little larger, you might want to consider the model 6210XT - 10" Round Wood Capacity, which, is the dual hydraulic feed version of the Model 6210. It also requires oil from your tractor, and sells for $7872.00. Speed Sensing is also available for this unit at $763.00
I ordered the 627XT, and is supposed to be in this coming Thursday, and I'll let you know more after I have had a chance to play with it.
Les