Breaking Eggs And Making Omelettes

Topics On Multimedia Technology and Reverse Engineering


Revisiting the Belco Alpha-400

August 25th, 2010 by Multimedia Mike

Relieved of the primary FATE maintenance duties, I decided to dust off my MIPS-based Belco Alpha-400 and try to get it doing FATE cycles. And just as I was about to get FATE running, I saw that Mans already got his MIPS-based Popcorn Hour device to run FATE. But here are my notes anyway.

Getting A Prompt
For my own benefit, I made a PDF to remind me precisely how to get a root prompt on the Alpha-400. The ‘jailbreak’ expression seems a little juvenile to me, but it seems to be in vogue right now.


When I last tinkered with the Alpha-400, I was trying to build a toolchain that could build binaries to run on the unit’s MIPS chip, to no avail. Sometime last year, MichaelK put together x86_32-hosted toolchains that are able to build mipsel 32-bit binaries for Linux 2.4 and 2.6. The Alpha-400 uses a 2.4 kernel and the corresponding toolchain works famously for building current FFmpeg (--disable-devices is necessary for building).

FATE Samples
Next problem: Making the FATE suite available to the Alpha-400. I copied all of the FATE suite samples onto a VFAT-formatted SD card. The filename case is not preserved for all files which confounds me since it is preserved in other cases. I tried formatting the card for ext3 but the Alpha-400 would not mount it, even though /proc/filesystems lists ext3 (supporting an older version of ext3?).

Alternative: Copy all of the FATE samples to the device’s rootfs. Space will be a little tight, though. Then again, there is over 600 MB of space free; I misread earlier and thought there were only 300 MB free.

Remote Execution
To perform FATE cycles on a remote device, it helps to be able to SSH into that remote device. I don’t even want to know how complicated it would be to build OpenSSH for the device. However, the last time I brought up this topic, I learned about a lighter weight SSH replacement called Dropbear. It turns out that Dropbear runs great on this MIPS computer.

Running FATE Remotely
I thought all the pieces would be in place to run FATE at this point. However, there is one more issue: Running FATE on a remote system requires that the host and the target are sharing a filesystem somehow. My personal favorite remote filesystem method is sshfs which is supposed to work wherever there is an SSH server. That’s not entirely true, though– sshfs also requires sftp-server to be installed on the server side, a program that Dropbear does not currently provide.

I’m not even going to think about getting Samba or NFS server software installed on the Alpha-400. According to the unit’s /proc/filesystems file, nfs is a supported filesystem. I hate setting up NFS but may see if I can get that working anyway.

Residual Weirdness
The unit comes with the venerable Busybox program (BusyBox v1.4.1 (2007-06-01 20:37:18 CST) multi-call binary) for most of its standard command line utilities. I noticed a quirk where BusyBox’s md5sum gives weird hex characters. This might be a known/fixed issue.

Another item is that the Alpha-400’s /dev/null file only has rwxr-xr-x per default. This caused trouble when I first tried to scp using Dropbear using a newly-created, unprivileged user.

Posted in General | 9 Comments »

9 Responses

  1. Vitor Says:

    You can easily workaround the md5sum issue using the following command for evaluating it:

    ffmpeg -f s8 -i file -acodec copy -f md5 –

  2. Mans Says:

    There is no need to run md5sum on the target system. There is also no need for exporting a filesystem _from_ the target. The target should mount the build tree exported by the host system.

  3. Multimedia Mike Says:

    Indeed, my comment about the md5sum command line weirdness was completely unconnected to FFmpeg or testing of the same. I just thought it was interesting.

  4. Michael Kostylev Says:

    Anyway, openssh-client would be not enough for sshfs, since the latter requires FUSE which isn’t supported by the stock kernel.

  5. Multimedia Mike Says:

    @MichaelK: True, but I was thinking about having the host mount a filesystem exported by the target. (sshfs on the host) -> (ssh server on the target). No go.

  6. Michael Kostylev Says:

    Btw, if you need more free space on /, fate-suite can be mounted over the network too.

  7. Multimedia Mike Says:

    That’s assuming I can make the NFS mounting work. But I will try.

  8. Michael Kostylev Says:

    If not, you’ll have to compile a new kernel.
    Back to SD, try ext2 (mount -t ext2 -o noatime) or even minix, it is hard to believe that nothing will work.

  9. RIck Hohensee Says:

    I’ve had mine for a year. Wifi is spotty, but that may well be due to physical abuse.

    Debian packages work, once you get some VTs. I’ve got gcc etc., but there’s a quirk in the linking step, so I just use it to look at how such-and-such would assemble on the MIPS.

    Anyone know how to get into U-Boot? I want to write a stand-alone Forth-like critter for the thing. If I can’t U-boot I guess I can bang on /dev/mem or rig up a kernel module to grab the thing.