1GHz PDP-11 (Re: Prints for an 11/70)

From: Richard Erlacher <edick_at_idcomm.com>
Date: Thu Dec 13 00:19:58 2001

I remember reading that a principal difference between a microcomputer, back in
the old days, and a minicomputer, was that the mini had an asynchronous bus.
That was, ISTR, a definition based largely on the DEC-realized version of the
minicomputer.

If it topped out at 7 MBps, it was probably because the bus handshake was
clocked with a CPU clock, in order to ensure the CPU would "see" the
transitions.

Dick

----- Original Message -----
From: "Dave McGuire" <mcguire_at_neurotica.com>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, December 12, 2001 10:55 PM
Subject: Re: 1GHz PDP-11 (Re: Prints for an 11/70)


> On December 12, Jeffrey S. Sharp wrote:
> > What little I've read about UNIBUS told me that UNIBUS has no set clock
> > rate, and that the speed of communication between two devices would be the
> > the highest rate that both devices could handle. If you've got nothing
> > but Sridhar-made fast devices on the bus, what stops you from having a
> > UNIBUS operating at say, 33MHz to 100MHz on average?
>
> I don't recall the specifics of Unibus...but its bandwidth is commonly
> stated as being about 7MB/sec. If that's the case, then it's unlikely
> that it's asynchronous. But perhaps it is asynchronous, and 7MB/sec
> was just the maximum.
>
> -Dave
>
> --
> Dave McGuire
> St. Petersburg, FL
>
>
Received on Thu Dec 13 2001 - 00:19:58 GMT