Workshop 5? You'll need to look in a museum. It was released back in 1998 or 1999 or something like that and probably stopped being supported around 2005. If ever it was available for download, it certainly isn't now. Are you sure that you have a specific need for WS 5? You can get the latest compiler (Oracle Solaris Studio 12 Update 2) for free, and it should be backwards compatible i.e., code written for and compiled with WS 5 should compile and/or link with Studio 12u2.