Ever wonder what it's like to run without hardware protection? Want to have direct access to all attached peripherals and disks directly? Enter real mode, an IA32 specific feature introduced with the 80286. This actually wasn't a new feature at that point, since the 80186 and the 8086 also had real mode. Rather, the 80286 introduced the distinction of real mode and protected mode.
http://en.wikipedia.org/wiki/Real_mode
I found it funny that in IA32, you can go from protected mode to real mode by resetting and keeping the contents of RAM alive. What a hack!
With real mode, you can't (shouldn't) access non-8086 extensions because it's nice to be backwards compatible. That being said, you really only have the basic ops available to you in real mode. That means no MMX or SSE for your homebrew BIOS =(
Interesting stuff =)
Saturday, May 30, 2009
Tuesday, February 24, 2009
Initramfs
So I'm back to working on my robot. This time, I want to add a camera (Logitech Quickcam Orbit AF - works with uvcvideo, even pan/tilt! Yeah! ) to it so I can implement a Visual SLAM solution and have it drive around the dorm and various campus buildings. To do so, I had to get a Verdex gumstix computer because the connex gumstix models didn't have USB host lines and the camera we have is a USB based device (duh).
As a result, I've been playing around with some of the nicer features of the verdex model I've just recently got. One of the best improvements in my eyes (aside from the lack of USB host lines! Grrr!) is the microSD slot included with the motherboard. Now I don't have to wait 6 minutes for a 115Kbps transfer of 30MB to flash the OS over the serial line. Plus, I can make changes to the filesystem and grab log files really quickly and easily by transferring the microSD card. (I would normally just scp it over, but it's nice to be able to do it faster sometimes, and when the network here at Rice is spotty, good luck!)
Now for the topic of this post, initramfs! I just wanted to link to a pretty good article that describes the motivations behind initramfs and why it's awesome.
http://www.linuxdevices.com/articles/AT4017834659.html
If there's one thing I appreciate online the most, it has to be the sheer number of records about computer history. Without these records, there would be no way for me to even understand why things are the way they are. Computers change so fast, 12 year olds growing up now will probably only see floppy drives in museums. =P That being said, Kernel development seems to go just as quickly. This means that for anyone new to the scene, (aka moi), understanding why the kernel is built the way it is gets harder and harder.
Anyway, that article was an interesting read on initrd vs. initramfs and the whole root= fiasco. Now I'm off to set up my Gumstix!
As a result, I've been playing around with some of the nicer features of the verdex model I've just recently got. One of the best improvements in my eyes (aside from the lack of USB host lines! Grrr!) is the microSD slot included with the motherboard. Now I don't have to wait 6 minutes for a 115Kbps transfer of 30MB to flash the OS over the serial line. Plus, I can make changes to the filesystem and grab log files really quickly and easily by transferring the microSD card. (I would normally just scp it over, but it's nice to be able to do it faster sometimes, and when the network here at Rice is spotty, good luck!)
Now for the topic of this post, initramfs! I just wanted to link to a pretty good article that describes the motivations behind initramfs and why it's awesome.
http://www.linuxdevices.com/articles/AT4017834659.html
If there's one thing I appreciate online the most, it has to be the sheer number of records about computer history. Without these records, there would be no way for me to even understand why things are the way they are. Computers change so fast, 12 year olds growing up now will probably only see floppy drives in museums. =P That being said, Kernel development seems to go just as quickly. This means that for anyone new to the scene, (aka moi), understanding why the kernel is built the way it is gets harder and harder.
Anyway, that article was an interesting read on initrd vs. initramfs and the whole root= fiasco. Now I'm off to set up my Gumstix!
Monday, February 9, 2009
Vi, editing the right way!
I've been brushing up on Vi because I'm tired of using gedit. As a result, I've found some fun documents on the intarwebs.
The following interview with Bill Joy, creator of vi, was posted in Unix Review back in 84. I loved reading it for the historical value and for the sheer, "WTF, $300 / MB!?!?!" factor.
Also, I love how he keeps referring to "scrunching" as "the thing that happens when you lose code." The fact that this had a word to begin with means it happened, a lot. God, I hope my code never gets scrunched. =P
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