Not according to this: https://en.wikipedia.org/wiki/Sun-3

The 3/50 was indeed a "pizza box" according to this, but Brad Spencer's images 7A and 7B he purports these are 3/50 boards: http://anduin.eldar.org/~brad/sunstuff/ - and those are definitely VME form-factor. Although, it's possible it uses only that "custom/private" third connector on the VME backplane?

On 3/28/2017 11:38 AM, Dan Cross wrote:

I *think* the 3/50 had a VME bus. As I recall, it was basically a single VME board mounted inside of a pizzabox case.

On Tue, Mar 28, 2017 at 11:27 AM, Larry McVoy <lm@mcvoy.com> wrote:

On Tue, Mar 28, 2017 at 11:23:49AM -0400, Arthur Krewat wrote:
> Is the 3/50 that much different than a 3/280?

Different bus structure as I recall. The 3/50 were workstations,
the 3/280 was big rack mounted VME (?) based system, mostly used
as file servers.