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LBA/CHS Bios Prob

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November 9, 2009 9:12:36 PM


One of my hard drives, for some reason, is being detected in Bios as CHS instead of LBA. I have 2 similar drives that are being detected correctly as LBA. How can I see if windows (Win 7) is using it correctly as LBA. I've heard what bios says doesnt matter, and Windows will use it as LBA if it determines it should use it as LBA.

Where can I find out if it's being used as LBA in Win 7? I've tried HDTune and it doesnt give that info. The drive seems to have about the same stats as the other drives on HDTune.

One of the bigger reasons I'm wondering is because I'm trying to diagnose the source of a rare system crash that's happening now and then. On Vista this crash did not occur, the computer system was identical except I did add some HD's. And I'm duel booting Vista on C: and Win 7 on drive H:

Also, in Bios I can only choose between Auto and LARGE when setting the HD access type.


Motherboard: XFX MB-N780-ISH9 LGA 775 NVIDIA nForce 780i SLI

More about : lba chs bios prob

November 10, 2009 12:50:18 AM

JoeyJoeJoe said:
One of my hard drives, for some reason, is being detected in Bios as CHS instead of LBA. I have 2 similar drives that are being detected correctly as LBA. How can I see if windows (Win 7) is using it correctly as LBA. I've heard what bios says doesnt matter, and Windows will use it as LBA if it determines it should use it as LBA.

Where can I find out if it's being used as LBA in Win 7? I've tried HDTune and it doesnt give that info. The drive seems to have about the same stats as the other drives on HDTune.

One of the bigger reasons I'm wondering is because I'm trying to diagnose the source of a rare system crash that's happening now and then. On Vista this crash did not occur, the computer system was identical except I did add some HD's. And I'm duel booting Vista on C: and Win 7 on drive H:

Also, in Bios I can only choose between Auto and LARGE when setting the HD access type.


Motherboard: XFX MB-N780-ISH9 LGA 775 NVIDIA nForce 780i SLI


Wow, I haven't heard those terms since the days of breaking that ~515mb hard drive barrier using a BIOS upgrade that you had to purchase instead of having the manufacturer upgrade the system BIOS. The LBA is for Logical Block Addressing and the CHS is the absolute of the drives characteristics Cylinders, Heads, and Sectors per track. The older BIOS systems only supported 1023 cylinders, 16 heads, and 63 sectors per track. That was back when MFM (modified frequency modulation) or RLL (run length limited) drive controllers were around and you had to modify your disc controllers firmware to talk to them. Now with the deprecated IDE systems and most system BIOS will control drives above 160MB you should not worry with such a modern motherboard especially if it's SATA. Now, perhaps if they were SAS drives it could be an issue. If you could provide additional information on your drives perhaps I could help. Sorry, about the digression into an ancient history lesson. Did you get the latest drivers from your chipset manufacturer for the drives and install them upon installation?

Regards,
Tom
former Phoenix BIOS engineer MicroFirmware
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a c 342 G Storage
November 10, 2009 12:56:38 PM

An important clue comes out of Tom Griffin's post and your disk size. Using only CHS access allows use of a HDD up to 515 MB, no more. That's 0.5 GB! So, if your disk is larger than that, it is NOT using pure CHS. LARGE was another method that allowed disks up to maybe 8 GB, but anything larger than that is sure to be using the LBA system. So unless you have a very old small drive, it is being used in the LBA mode.

You could try this to attempt to force proper identification of the drive. Although most BIOS's have the AUTO feature for disk detection during the boot sequence, they also have a screen where you can "manually" auto-detect your hard drives. Go there and pay careful attention to which drive is which. Concentrate on the one in question and have it run its auto-detect operation. Sometimes the result is two or three possible ways to use the drive and you get to choose which one. If you do that it will put those parameters in place instead of using auto-detect every time you boot.

If you do this, Save and Exit to finish booting, then go into My Computer and examine by READING ONLY the contents of that drive. If it all appears to be there and accessible, you're OK. BUT if the drive contents are wrong in any way, you have chosen the wrong set of parameters for drive access, and you should shut down, reboot into BIOS, and do this again making a different choice. As long as you don't try writing to the drive with the wrong access parameters this should not cause you any trouble.

Of course, maybe this won't make any difference, or maybe there isn't even such a tool in your BIOS. But try it if you can.
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November 12, 2009 2:57:54 PM

Ok, the CHS drive is definitely using more than 515MB. In fact it's a 1 TB drive. Windows doesn't seem to have a problem with it. So it must be using LBA.

I havent tried updating the bios in a while, maybe i'll do that at some point.

I did go to bios and ran the Auto-detect on each drive. None of the information changed. They all seem to detect the same cylinders, heads, etc.. but when the comptuer reboots it still lists that one drive as CHS.
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a c 342 G Storage
November 12, 2009 3:04:22 PM

Thanks for the update. It is puzzling that the BIOS Auto-Detect does not set it to use LBA mode. However, this may come under that wise old heading, "If it ain't broke, don't fix it!"
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November 13, 2009 7:39:28 PM

I have similar issue with my 1.5TB samsung drive
At first connect I connected it to the MB and it was recognized as LBA drive. I did partitioning and windows format NTFS. Then I connected the drive to another SATA-RAID cotroller on my PC, wrote some data on it and put it back on teh original controller. Now my drive is recognized as CHS drive, but wseems to be working OK.
My BIOS auto mode gives CHS an other option a can choose is large. In Windows I do not see anything different on the 500M en 1T partition I created.

Yeah maby if it an't broken....

but this is strange behaviour anyways.
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November 14, 2009 7:12:25 PM

I removed all partitions, changed the drive to dynamic disc vith windows XP computer management and then changed it back to basic disc.
After reboot my BIOS sees the drive now as LBA drive.
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