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<?xml version="1.0" encoding="gb2312"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312"/><title>linux for ppc chapter 3 jacobw </title></head><body><center><h1>BBS 水木清華站∶精華區</h1></center><a name="top"></a>發信人: plato (純真年代), 信區: Embedded <br />標 題: linux for ppc chapter 3 <br />發信站: BBS 水木清華站 (Wed May 30 23:09:22 2001) <br /> <br />Next Previous Contents <br />---------------------------------------------------------------------------- <br />---- <br />3. Target Hardware <br />Start by picking the processor which most closely matches your I/O requireme <br />nts, and work out roughly how much RAM and ROM space you need. Then see if y <br />ou can find an off-the-shelf board which also most closely matches what you <br />need. <br />3.1 CPU <br />4xx <br /><a href="http://www.borg.umn.edu/~grant/Linux/">http://www.borg.umn.edu/~grant/Linux/</a> <br />IBM 405GP <br /><a href="http://www.mvista.com/products/405gp_status/main">http://www.mvista.com/products/405gp_status/main</a> and <a href="http://www.chips.ibm.co">http://www.chips.ibm.co</a> <br />m/products/powerpc/linux/ <br />7xx <br /><a href="ftp://ftp.mvista.com/pub/Area51/ppc-7xx">ftp://ftp.mvista.com/pub/Area51/ppc-7xx</a> and <a href="http://www.chips.ibm.com/product">http://www.chips.ibm.com/product</a> <br />s/powerpc/linux/ <br />These devices are all covered in the MontaVista kernel. <br />Motorola 8xx <br /><a href="http://mot-sps.com/products/microprocessors/32_bit/mpc800/">http://mot-sps.com/products/microprocessors/32_bit/mpc800/</a> <br />Information from Motorola is fragmented, because the 850/860 and 823 are han <br />dled by different groups. Information about the bits they have in common is <br />generally equally applicable to both, so it's worth perusing the 823 resourc <br />es even if you're using an 850/860. <br />These devices are all covered in the MontaVista kernel. <br />823 <br />See the 823 Engineer's Toolbox at: <a href="http://www.motorola.com/SPS/ADC/pps/subpg">http://www.motorola.com/SPS/ADC/pps/subpg</a> <br />s/etoolbox/823/index.html <br />850/855/860 <br /><a href="http://www.motorola.com/SPS/RISC/cgi-bin/ncsp/ncsp.cgi">http://www.motorola.com/SPS/RISC/cgi-bin/ncsp/ncsp.cgi</a> <br />For non-Linux-specific technical FAQ's, see: <a href="http://www.mot.com/SPS/RISC/net">http://www.mot.com/SPS/RISC/net</a> <br />comm/support/ and especially: <a href="http://www.mot.com/SPS/RISC/netcomm/support/se">http://www.mot.com/SPS/RISC/netcomm/support/se</a> <br />archdb.html <br />603e <br />See: <a href="ftp://vlab1.iram.es/pub/linux-2.2/">ftp://vlab1.iram.es/pub/linux-2.2/</a> <br />Motorola 82xx <br />See <a href="http://www.mvista.com/.">http://www.mvista.com/.</a> <br />8240 <br />See <a href="ftp://ftp.mvista.com/pub/Area51/sandpoint-8240.">ftp://ftp.mvista.com/pub/Area51/sandpoint-8240.</a> <br />8260 <br />See: <a href="http://lists.linuxppc.org/listarcs/linuxppc-embedded/200002/msg00123.ht">http://lists.linuxppc.org/listarcs/linuxppc-embedded/200002/msg00123.ht</a> <br />ml and <a href="http://lists.linuxppc.org/listarcs/linuxppc-embedded/200008/msg00107.">http://lists.linuxppc.org/listarcs/linuxppc-embedded/200008/msg00107.</a> <br />html <br />AltiVec <br />AltiVec is Motorola's answer to Intel's MMX. See <a href="http://www.altivec.com/.">http://www.altivec.com/.</a> <br />See <a href="ftp://ftp.mvista.com/pub/Area51/ppc-altivec.">ftp://ftp.mvista.com/pub/Area51/ppc-altivec.</a> <br />3.2 RAM and ROM space <br />Linux has a slightly larger memory footprint than most conventional embedded <br /> operating systems when configured with equivalent options. This is the pric <br />e you pay to leverage the advantages of its enormous desktop user base, and <br />being able to share a common desktop and embedded environment. For most appl <br />ications the difference is insignificant, but if every last byte counts in y <br />our application, you might want to consider RTEMs or eCos instead. <br />Beware that commercial embedded operating system vendors often make meaningl <br />ess claims regarding the footprint of their micro-kernel, and the total memo <br />ry footprint (and often the royalties payable) increases substantially once <br />all the optional packages needed to provide the required functionality for a <br /> typical networked device are included. Work out what functionality you need <br /> before attempting to make valid comparisons. <br />For good architectural reasons, Linux isn't a micro-kernel. However, it does <br /> allow large chunks of code to be removed easily at configuration time. In p <br />ractice the architectural distinction between micro and monolithic kernels m <br />akes little difference to total memory requirements of the overall system. <br />Minimum memory requirement when using an initrd based root filesystem is gen <br />erally 2 MB of flash ROM and 8 MB of RAM, and here's what you can expect to <br />fit in: <br />8xxROM Monitor <br />Linux-2.2.13 kernel <br />minimal compressed initrd root filesystem with /dev, /etc, /var etc. <br />glibc-2.1.3 Shared C library, including pthreads support. <br />inetd Internet server <br />ftpd FTP server (for field flash ROM upgrades) <br />Medium sized Embedded C++ application ( 200 Kb) <br />This is the most common configuration because it attempts to minimize ROM sp <br />ace at the expense of RAM, since ROM is generally more expensive. However, y <br />ou can trade off ROM space to reduce RAM usage by using a compressed flash f <br />ile system and/or running the kernel directly from ROM. Both these options a <br />re more difficult, but have been successfully deployed and discussed on the <br />mailing list. <br />3.3 Commercially available boards <br />There are many off-the-shelf options including systems from Motorola and oth <br />er parties. If you're planning on building your own custom hardware, conside <br />r using one of the Single Board Computer systems listed below instead. You m <br />ay get by with just a custom daughter card, or may not need to do any hardwa <br />re of your own at all. <br />All the boards listed below are known to run Linux, although the degree of s <br />upport can vary. Mention to the vendor that you want to run Linux on the boa <br />rd, and they should be able to point you to the relevant files you need. The <br /> best supported boards are supported directly in the main kernel development <br /> tree, which is most evident by having a dedicated _MACH_... constant alread <br />y assigned in include/asm-ppc/processor.h. <br />If you still think you want to do a full custom design, pick a board from on <br />e of the following sources with the closest feature match to what you plan t <br />
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