You may be referring to the double unit dining cars. These were originally built for high volume trains like the Broadway Limited, Panama Limited and other trains. These were two full cars of that always ran as a pair with one car being the traditional dining car with kitchen and tables and the other car with tables only. The cars were connected by automatic doors so wait staff could move in between. Amtrak last used them on the Silver Service offering Buffet Style meals. One car had the buffet line and the other car had tables. Passengers helped themselves on the buffet line and then were seated. This was the only meal service offered on the Silver Trains in the late 1980s/early 1990s in one of the previous cost cutting attempts. The idea for this type of service came from the original pre-Amtrak Autotrain which offered buffet meals to customers. The buffet service did not go over that well on the Silver trains and the food offering was not that great. It was a far cry from the excellent meals served on the prior New York-Florida trains such as the Florida Special, Champions, Sliver Meteor and Silver Star and that service continued the first 10 years on Amtrak until Congress decided to "fix" the dining car deficit.
Ok, that's what I heard about from Mr. Haldeman when we talked...he mentioned that service was great in the early days (when they were still using a lot of the SAL/ACL/SCL equipment, I believe) and then it nosedived in the 80s with what you mentioned. He mentioned that, as a sleeper passenger, your one "big perk" at the time was that you got your buffet tray brought to you. As to the buffet/table cars...that feels extremely tragic, having those old twin units used for such substandard service.