Perrine@LOGICON.ARPA.UUCP (02/24/87)
On Friday 24 Feb, I "shot a query into the net" about the VAX 780 TBIA register and 4.2BSD moving a 1 there when the Architecture doc called for a 0. Here are some of the responses I received: >>From: john@basser.oz.AU (john%basser.oz@SEISMO.CSS.GOV) >>Yep. TBIA is a write-only read-zero register. The _act of writing_ it >>invalidates the translation buffer; what bit pattern you write doesn't >>matter at all -- the hardware totally ignores it. >> >>From: "Lew Doll" <led@j.cc.purdue.edu> >>It probably does not matter, since this register does not exist. It >>actually causes a branch in the microcode to a routine that invalidates >>each location, one at a time. >> >>From: Jason Venner <jason%violet.Berkeley.EDU@BERKELEY.EDU> >>This has been fixed in 4.3, with the most recent rev level, you must >>move a zero, previously a one worked correctly. Due to the response from the Berkeley person, and because we *are* running the latest HW/microcode rev, we will be rebuilding our 4.2 kernel to move the proper value to the TBIA register. I would advise others to consider doing the same. Tom Perrine ++ Logicon OSD ++ Perrine@LOGICON.ARPA