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LBA VS CHS Access Mode and HD install headaches

Z

Zarick

Senior member
I bought a 200gig Seagate HD. I installed it as slave as per seagate instructions, I ran seagate software, it copied everything over from my old C drive. Removed my old drive, setup the new seagate as only drive. No boot. I tried everything I could think of short of a clean install of xp.. no boot, did all the seagate instructions twice. No boot.

So I called Seagate tech support. We tried all that I had tried again. Then we tried doing it all in DOS. HD checks out great. But no boot to windows. Finally I notice something. I say.. the old hard drive is coming up as access mode LBA and the new HD is coming up at access mode CHS Does this matter? They say no shouldn't matter as long as access mode is auto detect in the bios.

So I fought for hours more, they finally said.. we aren't sure. Why don't you install a new copy of windows can call us back. Of course the windows install wont work.

Finally I am sitting there going.. Wonder if that should be detecting as LBA and isnt.. So I forced the drive to LBA in the bios. Redid my partitions, recopied everything. BAM works perfect.

Out of curiousity I set the bios back to autodetect and now it detects it as LBA access instead of CHS and the drive boots awesome (incredibly fast too).

So.. what did I do. did I hurt anything? Should I not have done that? Does this indicate something could be seriously wrong with my bios or the HD?
 
That's quite peculiar that your drive was being detected as CHS. Standard CHS limited ATA hard drives to 504MB. That's how old CHS is. LBA has been required ever since ATA surpassed about 8GB. You're not damaging anything by switching to LBA, that's what the drive is not only supposed to be using, but has to be using for anything beyond 8GB. It's not surprising the drive didn't work properly in CHS mode, but why it detected that way in the first place is anyone's guess, very odd. If it's working fine now, I wouldn't worry about it.
 
Here is the thing though. As a slave drive I could use all the harddrive even in CHS mode, I just couldn't use it as a boot drive.
 
hmmmy 200GB SATA Seagate drive shows up as in CHS mode in the BIOS when booting too.. My Raptor says its in LBA mode though.

With SATA there is no option to force modes though. So I left it like that. I notice no ill effects but it is kinda annoying it shows up as CHS.
 
Something had to be detecting it properly for all the capacity to be accessible by anything. You probably experienced something similar to the problems people were having with 48-bit addressing. Either the BIOS or Windows would detect it properly, so sometimes it would show the full capacity, but if both didn't, then it still wouldn't work regardless. I can't tell from your description what was detecting what, so the best I can tell you is that something was using LBA to see the whole drive, while something else was detecting CHS which would clearly cause a conflict accessing the drive.
 
I am pretty sure the bios was doing the chs stuff, and windows wouldn't boot until I put it in LBA mode so it must have been expecting LBA. Whats interesting is after I got it formatted and installed by forcing LBA mode it stayed detected as LBA by the Bios in auto mode.
 
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