Projects

FreeBSD netboot

We maintain our own version of the FreeBSD "netboot" code, and we use it for booting the 60 or so diskless X-terminals in the department. The FreeBSD people have deprecated the use of netboot in favour of the "etherboot" project, but we continue to use netboot. Our version includes support for the Intel Etherexpress Pro cards, building on FreeBSD 3.x, and more recently ELF kernel support. The code is available in my netboot working source directory.
We currently use flash chips in most X-terminals, and program them with a FreeBSD flash utility (Some newer versions of the Intel Etherexpress cards have an Atmel flash chip soldered on the board; for these, a special Atmel version may work).

MMDF

MMDF is the "Multi-channel Memo Distribution Facility", an ancient Mail Transport Agent (MTA) written around 1979-1986. We use MMDF to handle all mail within the department, but our version has changed almost unrecognisably from the original. As well as fixing a multitude of bugs and security issues in the original version, we have added many new features, and rewritten several sections of the code. Our development tree and (partial) change log are available.

FreeBSD libkvm tools

To help with debugging various FreeBSD kernel problems, I am slowly building up a selection of tools that use libkvm to print out various queues and structures from system core dumps. They can also be used (somewhat unreliably) on a quiet running system. So far I have:

mbstat : prints information about the proportion of the mb_map that is in use.
minfo : prints all mbuf chains, optionally printing contained data in hex.
nfsq : prints the contents of the NFS server input record queue (ns_rec) and the server cache.
tcpq : prints some TCP protocol control block information (unfinished).
vnq : prints a list of all vnodes, sorted by mountpoint.
fstat : a version of fstat(1) that includes information about socket buffer sizes, when printing info about sockets.

All of these tools are based on the the source code for FreeBSD's fstat(1).

1995 Irish Micromouse competition

I was on the team that built the winning entry at the 1995 Irish Micromouse competition. Some pictures and details are available.

Amstrad CPC

Before going to college, most of my experience of computers came from tinkering with hardware and software on the Amstrad CPC series computers. My CPC464 (which is in an attic at home right now) was substantially modified over the space of a few years; here are some of the additions:

Internal 3.5" floppy drive and disk controller. In the newer revision of the CPC464, the main circuit board is smaller, so there was room for a PC floppy drive between the circuit board and the tape drive. I also built a disk controller using a uA765 controller and lots of discrete logic (including a discrete logic digital PLL), and this fitted inside the case too. At the back of the controller board is a standard 6128-style edge connector for connecting in external drives. There is also a digital side-select switch which can be controlled either by buttons on the front of the box, or by a "|SIDE" command in software.
Internal 128kB battery backed-up static RAM, organised to emulate expansion ROMs. After loss of memory, the disk ROM image must first be loaded from tape before the disk drive becomes usable. Then other ROM images such as BASIC 1.1, Maxam and Protext could be loaded from disk. The RAM chip itself, and supporting logic are built piggy-backed on ICs on the main CPC circuit board.
Internal 512k expansion RAM. This is based on two 256k SIMM modules and quite a bit of support logic. It sits underneath the main circuit board, connecting to it via a DIP socket under the Z80 CPU.
8-bit printer port. Some of the other additions required some general purpose IO ports (RAM write protect, side switch etc), so I used one of these bits to add an 8th bit to the 7-bit printer port. Software in a custom ROM image intercepted accesses to the printer to deal with the 8th bit correctly.
Internal EPROM programmer (well, not entirely internal - it required an external socket and PSU). This was implemented by piggy-backing a second i8255 PIO chip on top of the existing one.
"|464" command. Some games and software wouldn't load with all the extra ROMS present, or with the 6128 ROM image. A new external command "|464" would immediately reboot the computer with all ROMs disabled. A full power cycle would restore all the ROMS again.

I finally got around to unpacking my CPC recently; here are some photos .