If you haven't read this post about dissecting the HD-A1, you should start there.
I got the flash disk connected and checked out the contents a little. After trying two different motherboards the USB connector was always in a completely inconvenient place, making it impossible to connect. So I ended up buying a USB cable and cutting it in half to expose the four connections inside. With a voltmeter I found the +5 and GND lines, and from there was able to figure out which were the balanced signal lines and get it connected and recognized by XP. The first attempt came up with a standard “autoplay“ message as it started scanning through the disk briefly. But it soon disappeared. At first I worried that this may have kicked off a routine to munge the first part of the disk! But I've since been able to get access to another HD-DVD player, and after doing about the same thing to read the image on its flash disk it still booted fine when placed back in the player. So no worries there.
When trying to put the daughter card from my unit into this other player it would reference the disk for a little while, but then halt partway through the boot process. So it looks like there's probably a serial number stored in the firmware, and a check performed during boot to make sure it's the right card for that unit.
In this 256 meg flash disk the Master Boot Record looked completely standard, with the common “Invalid partition table“ and “Missing operating system“ messages. The partition table in the MBR had a single entry marked as active for a 243 meg partition. It was set as type 0E, which means FAT16/LBA. (Not that the actual partition necessaraily has to be configured as such.) The boot sector was zeroed out.
After looking around sector by sector in the disk some more I saw what looked like ext2fs file entries, with these files and folders in the root:
In the first part of the disk there were some remnants of FAT32 entries scattered in a few sectors. The drive may have been originally formatted FAT32, and then repartitioned with ext2 from Linux. Early in the disc was the message “Red Hat Linux 7.3 2.96-110“, which could come from either Red Hat 7.3 or 8.0.
Lots of space is consumed with a plethora of PNG files. Probably all graphics are PNG.
Some of the more interesting messages I saw along the way:
"Copyright protector is working"
"The prohibited transaction was executed by the content"
"This disc is not available for this player"
"Failed to verify the content"
"High resolution output is prohibited for this content."
"Analog output is prohibited"
"This is a twin format disc"
"The certificate of the server you are trying to connect to has not been issued from a trustworthy certificate authority. However, all certificate dates are valid."
With the “twin format“ message it looks like provision was put in place for discs with one layer of old-school 4.7 gig DVD content and another of 15 gig HD-DVD content. Pretty neat! I think that the 480p message refers to trying to play back over the analog component output a high def disc that has its Image Constraint Token (ICT) flag set. Would be too easy for someone with a high def capture solution to simply snag the content in pristine high def and recompress it, so those contributing to the AACS spec put in a provision to dumb down the output if it's not going over an encrypted HDMI connection.
Looks like the unit will reference the Internet to verify the certificate for some protected content. We're moving steadily towards a more connected and more security-conscious world. I'm not sure that's all a bad thing. For sure the pirates out there will complain about the AACS guys strong-arming DRM on us, but altogether I'm not concerned. I'm not trying to steal content from anyone, so I don't mind if this kind of protection is in place. I'm just a curious consumer with a fascination with the latest high def video gadget out there.
There are some folks out there who think that Toshiba is losing money on the HD-A1. I think they are right. Quite a bit of high-priced silicon is in there, as well as obviously a ton of R&D work. I still don't know if this will pan out for them in the long run though. Some people have compared the HD-DVD vs Blu-Ray disc war to VHS vs Beta. There are strong parallels, but I also like to compare this to the more recent competition of two hybrid automakers -- Toyota and Honda. You can read more about that in this post.
UPDATE: I had a little more time to take a deeper look into the firmware, and found some additional tidbits.