Re: [TUHS] Origins of PPP

At the other end of PPP history, I’ve always felt that the best part of IP is that it will run, more or less, over a piece of wet string. In 2006 at SiCortex we were building a modest supercomputer with 972 six-core MIPS-64 chips connected by a rather nice high speed interconnect. The chips were booted over JTAG, which is another story, but in addition the chip had a “communications register” that could be written and read in I/O space from the kernel and over JTAG from the module level coldfire microcontroller. This was at first used for the console, and all 972 console streams were collected on a front end machine. However, it was a small step from there to multiplexing the comm register to provide two serial ports. We used the second one for PPP using a standard driver on the MIPS end and a somewhat strange JTAG driver on the coldfire end. This scheme let us SSH into the machine nodes when the high speed interconnect needed debugging. In spite of the bit-banging JTAG-ness of it all, it was usably fast at 100 Kbps or so. It was much easier to spin up PPP than to write a new network driver for this low-speed application.