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About nemrod

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  1. How To Overclock Your Raspberry Pi Overclocking the Raspberry Pi is a very simple process, but as with all overclocking results vary between chips so the only way to find out your own Raspberry Pi's limits is to experiment. The makers of the Pi have very conveniently created a file called config.txt located in the /boot directory. In this file you can set all kinds of settings, such as forcing HDMI, resolution, and yes, clock frequencies and voltages. Now, there are two things you can do. One is simply overclocking and leaving the voltages as they are, and the other is to also overvolt (increase the voltage to the chips) which results is more heat generated (shouldn't be much of an issue), shorter lifespan (in a higher degree than simply overclocking, but if I recall correctly we're still most likely talking years according to dom, one of the guys in the know) and a guaranteed voiding of warranty. Once you have tried overvolting just once a flag is set and your warranty is void forever. The upside to overvolting is, of course, that you can generally squeeze just a little bit more out of the chips increasing the frequencies, but some have reported not much higher frequencies even with overvolting compared to simply overclocking. It's up to you if it's worth voiding the warranty. Overclocking There are seven different frequencies you can change, here's a list of them (and their default values in MHz):arm_freq = 700 # frequency of the ARM processor sdram_freq = 400 # frequency of the SDRAM memory gpu_freq = 250 # sets all the following values related to the GPU (graphics processor): core_freq = 250 # frequency of the GPU core h264_freq = 250 # frequency of the hardware video block isp_freq = 250 # frequency of image sensor pipeline block v3d_freq = 250 # frequency of 3D block According to dom (in this thread: http://www.raspberry...php?f=29&t=6201) you will want all the GPU frequencies to be the same or integer multiples. That means if you change core_freq to 400 you will want to change h264_freq, isp_freq and v3d_freq to either 200 or 400 as well. To change the frequencies edit (or create if it doesn't exist) /boot/config.txt and add one or more of the above lines (without the # comments) and reboot. Your Pi will now run at the new frequency. As I mentioned before results vary between chips but squeezing it up to 800 for arm_freq, 450 for sdram_freq and 300 for gpu_freq seems to be a good starting point that most chips can reach without difficulty. From there you can increase the different values incrementally until you hit your limit (resulting in crashes and kernel panics and general stability issues). Overvolting Again, overvolting will irreversibly void your warranty. Proceed at your own risk. The two values (maybe exclusively the first) you may want to touch are the following: over_voltage = 0 # CPU and GPU voltage, 0 means 1.2V with each positive or negative step representing 0.025V. 1 is 1.2+0.025=1.225V and so on over_voltage_sdram = 0 # voltage for the SDRAM, works just like the previous setting. This, just like gpu_freq, breaks down into three different values, but unless you know what you're doing I don't suggest touching this or them. I don't see much talk about it so I suggest you don't fiddle with it without further research. It seems to be a generally bad idea to go over 8 on the over_voltage setting, with most people seemingly settling in at 6. When you've found a nice clock that runs stable I think the community would appreciate you adding your values to the table at the bottom of this page to help future overclockers in their endeavour: http://elinux.org/RP...t#Tested_values Author nemrod Category Raspberry Pi Tutorials / Guides / How-To's Submitted 06/27/2012 12:40 PM
  2. Full guide to Arch Linux on the Raspberry Pi This guide assumes basic knowledge of how to extract zip files and downloading files. The first step is of course to download the Arch distribution for the Pi from the Raspberry Pi downloads page. Once you have done so extract the zip file and you'll end up with a .img file (and a SHA1 hash file to verify, but let's ignore that), which is what we need to put on the SD card for the Pi to boot from. The next step differs between your host OS, i.e. if you're using Windows or Linux to create the SD card. Either way, start by inserting the SD card (it will be wiped, remember to use one with nothing important on it). If you're using Windows download Win32 Disk Imager, extract and run Win32DiskImager.exe. Select the device (make sure you choose the correct one or you'll end up corrupting something you shouldn't have) and pick the .img file we extracted in the first step. Click Write and you're done! If you're using Linux you'll instead want to insert the card and run "dd if=path/to/img/file of=/dev/device bs=1M" as root. To find out what device the card is you can run dmesg, 5-10 lines should appear at the end starting with something like "sd 0:0:0:0: [sda]", where sda is the device. An example line could look like this: "dd if=~/archlinuxarm-29-04-2012.img of=/dev/sda bs=1M". It won't print any progress so just wait patiently until it's done and returns you to the command line. Now that you've got Arch on an SD card the next step is booting it up. Insert it into the Pi, connect your peripherals and you're good to go. Note that unlike Debian Arch has SSH activated by default and so you don't need to connect a monitor and keyboard as long as it's got network connectivity. Now you probably want to resize the partition to match the SD card since there is likely to be a lot of unused/unusable space by default. Log in with username root and password root (either via SSH or with a keyboard and screen connected to the Raspberry Pi, either will work). Run "fdisk /dev/mmcblk0". Type the command 'p' and press enter. You should see two lines looking similar to this: /dev/mmcblk0p1 1 195312 97656 c W95 FAT32 (LBA) /dev/mmcblk0p2 197265 15544319 7673527+ 83 Linux Those are the current partitions. What we need to do is delete the second one and recreate it larger. Make a note of the first number on the second line (in this case 197265) and then type the command 'd' (and press enter). Choose 2. Now we create a new one with 'n' and enter 'p' for primary and 2 for partition number 2. Now we get to the first sector, and here it's important that you enter the number we took note of earlier, in this case 197265. Select the largest value for last sector. Now that we've done that enter 'w' to write and then 'q' to quit. Reboot with the command 'reboot' and once you've booted and logged in again run 'resize2fs /dev/mmcblk0p2'. It'll take a while to complete but once done you'll be able to utilise the full size of the SD card. The next step is to update the system so you have the latest software running. Normally you would just need to run 'pacman -Syu' to update, but some manual intervention is required because of some recent changes. I won't go into much detail, I'll just give a list of commands to execute. This is from memory when I did this a couple of days ago, so give me a shout if something seems not to be working. pacman -Sy pacman pacman-key --init pacman -S archlinux-keyring pacman-key --populate archlinux pacman -Syu --ignore filesystem pacman -S filesystem --force It will ask if you want to replace for example udev with systemd-tools etcetra, and yes, you do. Once that's done you should have a fully up-to-date Arch Linux system on your Raspberry Pi! Extra tips To enable sound edit /etc/rc.conf and add snd-bcm2835 to MODULES like so: MODULES=(snd-bcm2835) You can also change hostname in the same file (the HOSTNAME variable), which takes a reboot to take effect. To create a swap file (which is a good idea in case you end up in a situation where you need one) run the following commands (taken from Arch wiki): fallocate -l 128M /swapfile chmod 600 /swapfile mkswap /swapfile swapon /swapfile and add "/swapfile none swap defaults 0 0" to /etc/fstab. You might want to limit writes to your root partition by disabling atime and diratime (sets a timestamp of latest access). For normal usage there are no real benefits to having them enabled while it can give you a performance boost (and can boost your cards longevity) to disable them. Here's how your fstab might look: devpts /dev/pts devpts defaults 0 0 shm /dev/shm tmpfs nodev,nosuid 0 0 /dev/mmcblk0p1 /boot vfat defaults 0 0 /dev/mmcblk0p2 / ext4 defaults,noatime,nodiratime 0 0 /swapfile none swap defaults 0 0 If you have any additional tips or questions post away! Author nemrod Category Raspberry Pi OS Installation Guides Submitted 06/24/2012 06:05 PM
  3. Not sure how this is supposed to work, but I've written a couple of tutorials but haven't received any PM.

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