From mboxrd@z Thu Jan 1 00:00:00 1970 From: dave@horsfall.org (Dave Horsfall) Date: Thu, 30 Nov 2017 09:42:51 +1100 (EST) Subject: [TUHS] UNIX on S/370 In-Reply-To: <20171121024111.GO9146@mcvoy.com> References: <201711200350.vAK3omwQ013495@freefriends.org> <20171120195618.GK9146@mcvoy.com> <05af01d36259$5e0873e0$1a195ba0$@ronnatalie.com> <20171120234515.GB9093@mcvoy.com> <20171121024111.GO9146@mcvoy.com> Message-ID: On Mon, 20 Nov 2017, Larry McVoy wrote: > So tape I can see being more weird, but isn't raw disk just "don't put > it in buffer cache"? DMA too, hence the process is locked in core. I think the read/write had to be a multiple of 512 bytes as well (I lost my Edition 6 manuals along with my treasured -- and original! -- Lions books in a house move). > From what I've been able to gather early tape in Unix was dicey, > something about the driver doing seek. Was there more to it than that? IIRC, the driver kept track of the current block under the head, and issued forward/backward skips accordingly; I have no idea whether SimH gets that right (as opposed to doing a random seek). (It bloody well worked, Mr Minnich, OK?) -- Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."