MR M T Golledge wrote: >However, I'm concerned with the specifications of the PC and would like your >thoughts before I get going (I expect further down the line I'll get a >separate server as at the moment I've only got a couple of 40Gb hard drives >in the PC therefore a total of 80Gb - I don't think my motherboard will be >able to cope with anything higher than 40GB looking at the Intel website): > > What, do you think we're talking about Windows? ;)
The motherboard's BIOS may have a limit on the size of HDD it can access. Therefore, any kernel that uses the BIOS for accessing the HDD (like the DOS/Windows kernels) can only access data that falls within the first <limit>GB of the HDD. Fortunately, BIOS and chipset manufacturers did Linux users a great big favor by creating BIOS's with varying and severe bugs. Therefore, when creating the code to access HDD's in Linux, developers had to choose between writing code to deal with all the bugs in the BIOS's (i.e. like the Via 4-in-1 drivers, or the Intel Bus Master drivers, or any of the other IDE drivers you have to install in Windows) or to completely circumvent the BIOS. The second solution--although it required a bit more up-front development work--was determined to be significantly easier in the long term (for Windows, the first solution was easier because Microsoft left development of the drivers up to the BIOS/chipset vendors). Therefore, Linux does /not/ use the BIOS to access the HDD. However, you still need to allow the BIOS to access enough of the HDD to execute the boot loader and possibly for the boot loader to find the kernel. On Linux, you have two options. First, you can create a small partition at the beginning of the disk that contains your "/boot" directory (i.e. a boot partition). If doing this, you can often let the BIOS autodetect the drive (which it may say is a 33.8GB HDD even though it's much larger), and once you're in Linux, you'll have access to the entire drive. Some BIOS's, however, will refuse to autodetect the HDD if it's greater than the maximum supported size. If so, you just manually specify the HDD parameters in the BIOS (i.e. 16383 cylinders, 16 heads, and 63 sectors--making the BIOS see the HDD as an 8.4GB drive) and make sure your boot partition (or at least the /boot directory) is within the first 8.4GB of the HDD (I generally make an 8-, 16-, or 24-MB partition--depending on the function of the system--at the beginning of the HDD for /boot). Note that when specifying a disk geometry, having a separate boot partition may not be required, but generally makes things much easier. If the disk isn't your boot disk, things are much easier. Just tell the BIOS that the disk doesn't exist (i.e. put "None" in for IDE 0 slave or whatever). I used to have a Pentium 100/MMX that had a 2.1GB BIOS limit (and wouldn't detect drives larger than that size) and I ran it with a 200GB HDD without problems (until lightning took out the motherboard--stupid cable modem). Now, I have an AMD K6-2/380 with an 8.4GB limit using an 80GB HDD for a boot disk. The one problem, though, is that although you buy an ATA 6 (UDMA/100) HDD, you'll be using a much slower access mode--which seems a waste. Your motherboard is likely to only support UDMA/33 or UDMA/66 (my Pentium 100 used PIO Mode 4, my K6-2 uses UDMA/33). UDMA/66 probably isn't a problem, but UDMA/33 may be depending on number of tuners, settings for commflagging and transcoding, etc. Many HDD's also have a jumper that allows you to set them to appear as small disks. I've never used this approach. Some of these just make the disk report its geometry to the BIOS differently, but others completely disable access to the rest of the disk at the HDD level (so even Linux can't work around it). Generally, Linux users shouldn't use the jumpers on disks to change perceived disk size. Oh, and make sure you don't have a disk manager on the disk (i.e. never stick one of those floppies that comes with the hard drive in the floppy drive). See http://tldp.org/HOWTO/Large-Disk-HOWTO.html for details. That being said, though, IMHO, getting a "dirt-cheap" new computer may be worthwhile to allow for better commflagging. I highly recommend something in the 2GHz (or, in AMD parlance, 2000+ ;) range. All you need for a dedicated Myth backend is a case/power supply, motherboard with integrated audio/video/LAN, CPU, memory, and hard drives (no need for floppies or CD/DVD). If you forego the integrated video, you can get a GeForce 4 MX440 and make it a combined backend/frontend (and add a DVD if you want to use MythDVD). Don't know about UK prices, but I've purchased about 20 systems (one by one) like this over the last couple of years for about $150 each in the US. However, I may not be well-qualified to make this recommendation as I just upgraded my AMD Athlon XP 2000+ combined frontend/backend to a dedicated AMD Athlon X2 4800+ frontend and an Athlon XP 2400+ backend for a high-def setup, so, obviously, I feel my Myth box is worth spending some money on. Mike _______________________________________________ mythtv-users mailing list [email protected] http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
