/usr/home vs /home

[Doug Hardie]

On 20 February 2012, at 22:20, Chip Camden wrote:

>>> I believe the 5MB removable were RL01.  They also had a 10MB removable
>>> RL02, which we used for software distribution.  We resold them to our
>>> customers at $170 each.
>> 
>> yes, this sound familiar. The RL02 came later.
>> 
>> I think that tapes were much more common for software distribution those days.
>> 
>> I still remember the responsiveness of RSX-11 even compared to FreeBSD under all circumstances. Real time is real time.
>> 
>> Erich
>>> 
> 
> Oh man -- we wrote process control software in Fortran-77 on RSX-11M to
> automate our software distribution processes.  That was the best!  DECNET
> to communicate between systems.

RSX-11D was slicker than greased lightning.  Used it for a number of systems.  The first 30 pages of the kernel source were the documentation.  The description of every table and the values for every field.  What each module did was documented at the top of the module.  I made numerous improvements to the kernel most of which were adopted by DEC.  However, it was nowhere near a fully featured OS.  It was quite bare bones.  Great for real-time requirements.  There was a guaranteed maximum time that interrupts were disabled and it was very small.  We interfaced a number of instruments to it and none of them ever saw any delays.  Most of them automatically fed data to the computer.  There was no triggering of that.  The instruments just pushed the data.

The RK05 had one removable platter in a plastic housing.  It used a voice coil movement mechanism that had to be aligned every week or you would lose your data.  It didn't hold much and was quite slow.  We used those at first but the system couldn't quite meet its performance requirements.  I still have one of those platters on my wall at home.  Departure present from the unit.  That particular platter had a head crash so the remaining oxide had to be sanded off to sanitize it.  The timing side is out with lettering on it now.  We used 4 RK05s in one rack and each was mounted as a separate disk.  The controller was single threaded so you couldn't get any performance improvement with creative disk assignments.

We switched to 5 platter drives RP04s which were extremely reliable and didn't need frequent maintenance.  They also ran much faster than the RK05s and held more than 10 times the data.