Porting Linux to the DEC Alpha: The Kernel and Shell

After showing off Linux/Alpha at DECUS, it became clear that some kind of end-user-installable distribution was needed. At that point, Linux/Alpha resembled in some ways the early days of Intel Linux: the “system” consisted of a motley collection of source and binary archives scattered over several FTP sites on different continents. Putting together a running system out of these pieces was a job only a dedicated hacker would be willing to go through with.

One difference between then and now is that now there are high-quality commercial Linux distributions (Plug-And-Play, Red Hat, and Slackware, to name just a few) that can serve as the basis for equivalent Linux/Alpha distributions. We knew, though that it would be some time before these distributions were ported and qualified for Linux/Alpha. In oder to sustain the momentum built up at DECUS, we needed some kind of Linux/Alpha distribution sooner than that. That's when we decided to embark on a project designed to become obsolete: BLADE. BLADE stands for Basic Linux Alpha Distribution Expletive (I picked the name by starting with “LAD” for “Linux Alpha Distribution” and grepping through /usr/dict/words for this combination and playing acronym games with some of the results). BLADE is a Linux/Alpha kit that can be installed without needing to build kernels or use a host development system.

BLADE was designed to be deployed quickly, and it's pretty rough around the edges. There's only one automatic installation script, called install_subset. A lot of steps that are done automatically by other distributions must be handled manually in BLADE. We provide full step-by-step instructions, though, so the user knows what steps need to be taken.

The first release of BLADE (V0.1) provided basic functionality and a development system in character-cell mode. There was no networking, no GUI, and a limited utility set. However, it was self-hosting, and it came with kernel sources and the gnu compiler suite. One could build the kernel or any utilities one desired using BLADE. In fact, we used BLADE V0.1 as our primary development system for BLADE V0.2. BLADE V0.1 was based on a modified 1.2.8 kernel and supported the AXPpci/33 only.

The second release of BLADE (V0.2) added more utilities and networking functionality. Graphics were still not available, but one could perform development and basic networking (ftp, telnet, rlogin) in character-cell mode. BLADE V0.2 was also the first release to support the Linux/Alpha Miniloader (aka MILO/Alpha) on the AXPpci/33. MILO is a drop-in system firmware replacement that allows the user to boot and run Linux without requiring the SRM console firmware. BLADE V0.2 also added a kernel boot disk for the Digital Semiconductor 275-MHz EBPC/64 evaluation motherboard. This is the fastest system to date that supports Linux. BLADE V0.2 is also based on the modified 1.2.8 kernel.

Currently under development is BLADE V0.3. BLADE V0.3 will be based on a 1.3 kernel and will add support for the X window system (see below). It should also support more system types.

Thanks to the tireless efforts of my colleague Jay Estabrook, as of this writing X11R6 is up and running on Linux/Alpha. Most of the standard libraries and client executables are in place. At the present time, only the S3 server has been ported, and it has only been qualified on a few video cards. The current plan is to let this be a sample server and solicit other parties (e.g. the XFree86 Consortium) to port other servers.

One major problem with supporting multiple video cards has to do with the on-board ROM BIOS that many cards have. This BIOS typically contains code to initialize the card and to set video modes. Unfortunately, this BIOS is nearly always written in 80x86 assembly code. To execute it on an Alpha system requires an Intel execution engine. We are investigating several strategies to provide this functionality as part of MILO/Alpha in source form, and rumor has it that our old friend David Mosberger-Tang has made good progress in this area.

As I write this, Linux/Alpha is being exhibited at UNIX Expo in New York City in all of its X-windows glory. We have ported the freeware web-browser chimera, and these systems are available for surfing the web and for connecting to remote systems on the Internet via rlogin, telnet, and ftp. In fact, on setup day several people from non-net-connected boths came by to use these systems to retrieve forgotten files from their home systems. This includes yours truly, embarrassingly enough. We needed to connect to the serial port on our PC64 system to use the ROM debug monitor, but the version of Linux/Alpha on the other system did not have kermit, cu, tip, or any other terminal emulation or serial connection program. No problem: I ftp'ed over to David Mosberger-Tang's archive at ftp.azstarnet.com and retrieved the Linux/Alpha version of kermit. We were in business in a few minutes.

In short, Linux/Alpha is starting to feel like a real Linux system!