Robots again

From: Captain Napalm <spc_at_armigeron.com>
Date: Mon Mar 16 15:53:28 1998

It was thus said that the Great Tim Shoppa once stated:
>
> > [Hmm... TOPS/PC...]
> >
> > Hmm... Port TOPS to the PC/Alpha/Etc...
> > Kinda above me, but if someone did an ITS or TOPS port to the PC or VAX,
> > I'd run it as soon as I could get it installed!
>
> It wouldn't be easy. Unix is available on so many different systems
> because it's a "lowest-common-denominator" OS, and requires very little
> hardware support. Porting a OS like TOPS, ITS, or VMS is much harder
> because most hardware simply doesn't have the requisite features to implement
> things which are basic to the OS.
>
> VMS has been ported to the Alpha, but it needed PALcode support to ensure
> that things like queue element insertions/removals could be done without
> interruption.

  Well, that's because on the VAX (to bring classic computers into this) had
an ENQUEUE and DEQUEUE (I think those are the mnemonics) instructions which
handled double linked lists (of which queues and stacks can be built out
of).

  Why the need for PALcode to do that on the Alpha is a bit odd - all you
really need is an instruction that does an atomic "test and set" to ensure
atomicity (hmmm, it could be that instruction they added, although it seems
strange because DEC Unix supports multiple CPUs and you NEED that for
multiple CPUs).

  I must admit that some of the features of old OSes (like VMS, TOPS-x0 and
ITS) are neat and it's a shame that it's taken some 30 years for some of
them to make a comeback.

  -spc (IMHO - the two worst things to happen to this industry are
        Unix and Microsoft. Both promote the lowest common demoninator
        oddly enough)
Received on Mon Mar 16 1998 - 15:53:28 GMT