What is ISCAS85 benchmark?
I'm writing a paper on the history of the benchmark circuits, and so found this question. Here is the story.
The ISCAS'85 benchmarks were collected and published to help in comparing automatic test generation (ATPG) tools. They were presented at the 1985 International Symposium on Circuits &amp; Systems. At ISCAS'89 a set of sequential circuit benchmark circuits were presented to spur the development of sequential ATPG. (I was on the ISCAS'89 panel.) These are often used in combinational form, with all internal flops made into pseudo-primary inputs and outputs.
In 1999 I collected another set of benchmarks, a bit larger and more complex, and presented them in a panel at the International Test Conference. These are called the ITC'99 benchmarks. I also co-edited a special issue of IEEE Design &amp; Test of Computers (now just IEEE Design &amp; Test) on the benchmarks.
I was unaware they were also used for synthesis.
The circuits are available on line - Googling ISCAS85, ISCAS89 or ITC99 will lead to many writeups and papers. 
Scott Davidson