Christopher J. Vogt
Fri, 3 Apr 1998 09:43:37 -0600
At 8:48 AM -0600 4/3/98, email@example.com wrote:
> Date: Fri, 3 Apr 1998 09:26 EST
> From: Chris Bitmead <chrisb@Ans.Com.Au>
> > It is an application under Unix. There was talk of extending it to
> > taking over the whole machine, but that has (so far) never been done.
> > Genera, on which it is based, is an entire operating system which runs
> > on (among others) the Ivory chip architecture which Open Genera's
> > emulates.
> To what extent is the Ivory chip specialized for running Lisp?
> What features does it have that make running Lisp fast?
>Most importantly, it carries the 8-bits of tag through the entire datapath and
>memory interface. The microengine can do tag comparison and dispatch in
>with an operation, so for example an add instruction can assume that the
>are both fixnums and start doing the addition at the same time that the tag
>comparison hardware is comparing the tags. If there is a mismatch, that
>causes the result not to be stored and a trap to be taken.
>The tags are not only used to identify datatypes, but also for internal
>i.e. the copying garbage collector has GC-FORWARD tags to serve as a
>for an object whose contents have been moved but for which there might
>references in virtual memory using the old addresses.
>CDR-coding, headers for compound structures, locatives, logic-variables,
>the instruction stream all use tag bits, and hence the tag checking
>is on the chip.
>The chip also has hardware support for ephemeral garbage collection, an
>to a co-processor, a way to do efficient burst mode transfers on the
>and a special limited mode (FEP mode) for running some much more stylized Lisp
>code the load the virtual image, etc.
Kalman, did anything ever get published on the I-machine architecture? I can't
seem to find anything.
Here are a couple of references I dug up about Genera and the 3600 architecture
that might be informative to those interested but unfamiliar with the Symbolics
Symbolics Architecture - IEEE Computer, January 1987
The Symbolics Genera Programming Environment - IEEE Software November 1987
Christopher (Chris) J. Vogt - Computer Consultant - Lisp, AI, Graphics, etc.