Jack- a rotating drum blower has an opening in the outer drum housing to each side usually the inner drum rotates from side to side sending the snow either out one of the holes or up the chute. Because you don't have the resistance of the chute you can move more snow with the horsepower, but you also can't control where it goes
see :
Normand N86-282HTR Side Discharging Snow SnowEquipmentDealer.com - YouTube
Schulte Snow Blowers SDX-12, RDX-12 - YouTube
I did once enquire of pronovost whether they could or would make a rotating drum pull behind and they said they had never been asked. I think that most of their rear pull production gets used commercially and typically those are used on larger tractors on smaller drives. The reasons for the larger tractors that i see listed are not to be able to drive thru the snow but for faster transit times and to accommodate the greater weight of the rear pull when traveling at speed and lifting/lowering cycles of 100's to 1000's of times per day. Too the saving of seconds from greater horsepower and travel speed add up when clearing hundreds of drives.
As far as leaving frozen tracks i have never had an issue, can't see the stuff freezing in the time it takes the tractor to move 3 or 4 feet (half second or less) and the blowers weigh more so they may in fact scrape better.
regarding the rest of the thread i always find it interesting that those of us that have tried rear and front blowers and actually have rear pulls are dismissed or a blanket statement of that that can't work here or will leave frozen ruts is used
google "switching to a blowing service" its an over 100 page thread devoted to commercial snow removal with blowers, within that largely the weapon of choice is the rear pull- in this instance its used because its much faster than even plowing or smaller drives. Too, those contractors claim that they leave a much cleaner product, do less damage and allow them more frequent visits while charging less at a greater profit. Many of those folks (most) are based in areas where it snows more than 3 inches, the snow does not melt in between and the snow has moisture in it. In my use i clear my drive faster than i did with a blade (or front blower) , i get a better result and its so easy to use i clear my main drive more often. There is no way i would ever drive as fast with a rear push as i do with my pull.
I wonder if folks are stuck on the old style single stage rear pulls? B and d's comment about 9 N's seems to be about those.