On Wed, 6 Sep 1995, Brad Walker wrote:

> David S. Miller wrote:
> > At the very least, non-availability of documentation.  Also the
> > non-disclosured nature of the sun4m architecture specification
> > although most of what is in there can be easily reverse engineered and
> > learned through trial and error but this takes time.
> > 
> Hum.. I've found a bunch of documentation in the public domain:
> 
[list of docs snipped]
> 
> All of the above can be gotten by calling. There might be a simple charge
> of $50 or so. But, that's to be understood. The above documentation 
> can get you going in the right direction quickly.

Yes, these can all "get you going"--but they're not enough to make it 
all the way through. I have pretty much all of these things, and they
do cover a lot of ground. But they don't cover many of Sun's fancy
enhancements to the plain Sparc8 architecture--like the IOMMU or IOCACHE.
The IOMMU, for example, is partially documented in the MicroSPARC
processor manual, but its register set doesn't correspond to the 
IOMMU in the SS10/SS20 except for the first two or three registers,
as far as I can tell from poking the machine. I have seen no 
documentation on the iocache anywhere, except in a SunOS header file that
was unusually brief and uninformative. All I know is that there's a "c"
bit in an iopte. There are other similar gaps in the public material.

--Aaron