30 Nov
2017
30 Nov
'17
4:42 a.m.
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."