Hi, I want to install QNX 4.25 on a PC104. My problem is that it detects a disk with 993 cylinders, 32 heads and 63 sectors instead of 1987,16,63. I tried ‘install -p -c 16,1987,63’ but it says Invalid option (‘c’). What am I doing wrong ?
thanks,
aladiah
That’s not a problem, that’s the effect of LBA (logical block addressing). What is important is the geometry is the same as seen by the BIOS. Make sure LBA is enable in the BIOS.
thanks, Idid check the LBA is enabled, but it found also the disk to be 977 MB instead of 1 GB. How do I resolve that ?
thanks
aladiah
You can’t.
See if real geometry is 1987,16,63 that mounts to 19871663 = 1,025,482,725. With LBA you get 9933263*512 = 1,024,966,656. LBA causes a lost 516069 bytes. If the number of cylinder would have been even instead of odd there would be no lost.
But you may ask well that doesn’t explain the drop from 1G to 977Mb. You are getting confuse by a trick often used by HD manufactures. They will state 1G as in 1,000,000,000. That is not the case in the computer world, when someone tells you there is 1K of ram in a system that actually mean 1024 bytes not 1000. Same for HD, 977M is in fact 97710241024 = 1,024,458,752. The number aren’t the same because 977 is probably rounded. To be precise you have 977.484375M.
So it comes down to unit. HD manufacturs use Gig has in Billion, while everything else in the computer world used 1024 as the unit for 1K.
thanks very much, I’m learning a lot !
I’m reinstalling in fact the os and before that I checked in fdisk /dev/hd0 and I get the same informations (sectors, cylinders …) than the one the system auto-detect during the installation, which is different from the BIOS. Do I keep on going with the installation with the data from fdisk /dev/hd0 ?
Yes installation should be fine. BIOS is showing you physical property of the disk and not the disk presented by the BIOS to the Os.
thank you, I begin the installation, sorry for all my questions 
No problem that`s what this forum is for i guess!