Either production-quality open source code, or pedagogical code. I'm looking at the Stanford Pintos kernel and MIT xv6 kernel. While there were minor papers from those projects, I think they were more like a labor of love. When you consider the coding effort, those projects probably took 10x the effort than a typical paper.
But yeah it would be better if a little more time was spent on code vs. papers.
I actually attended a talk from an Adobe researcher talking about software abstractions some years ago. He advocated that you should be able to get a Ph.D. for finding a good abstraction, e.g. for say modeling a paint brush or something. There are lots of bad ways to write code but only a few good ones. Even better would be to write it in a way so that other people can actually learn from it.