[TUHS] UNIX on S/370

Dave Horsfall dave at horsfall.org
Thu Nov 30 08:42:51 AEST 2017

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."

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