# Hard Disk--15-Heads or 16 Heads--What's the diff?



## Alex Ethridge (Apr 10, 2000)

I have an IBM hard disk model IC35L080AVVA07-0. It has jumper settings for 15-heads and 16-heads. This drive came 'bare' (without documentation) so I have no idea why or when to use either of these settings and I can find nothing about it at the IBM site. It came from the factory with settings for 16 heads so, not having anything to tell me different, I left it at that.

The reason I am asking is that the drive was set up and worked fine for several months. Later, I moved it to another machine with a slightly older model main board. It _seemed_ to run fine for about 3- or 4 weeks; but, then I began to notice corrupt file names in Windows Explorer that did not show as corrupt in DOS mode. Last night, I did a massive file copy from one machine on the network to the machine containing the IBM drive in question. This morning, I got up to find the primary partition on the IBM drive was "Invalid Media Type" and the partition type was "Unknown" by FDisk.

Now, I don't know if this is related to the 15-head-16-head settings or not. But, until I have some documentation on this, I will never know for sure.


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## kilowatt1 (Oct 27, 2001)

Look at THIS  link for some general info. about it.

Edited for correct URL.


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## tjsudo (Jul 27, 2000)

Hi,

If you are running Win95A, 15 is the limitation.
For other Windows OS, use 16, especially for win2k. They have problem with large 15 drive.

For your problem, did you try fdisk /mbr?

TJ


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## Alex Ethridge (Apr 10, 2000)

Using Win98B.

I have already deleted the partitions and am waiting on the info about this 15-head-16-head thing before I re-FDisk again.


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## tjsudo (Jul 27, 2000)

Is it possible that your bios is not Int13 capable?
What's the size of the drive.
If it's more than 8.4GB and showing only 8.4GB, need to update the bios for INT13.

TJ


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## Alex Ethridge (Apr 10, 2000)

It's an 80-Gig; but, there was a 60- in there for several months and there was no problem. I'm formatting the drive in that machine as I write this. I think I will just set it up again and hope for the best. Its work is not mission-critical anyway.


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## ~Candy~ (Jan 27, 2001)

Have you thought about using a software overlay program on it.......


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## Alex Ethridge (Apr 10, 2000)

Overlays can be dangerous and should be used only when nothing else will do.


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## ~Candy~ (Jan 27, 2001)

How so? I've used them off and on for years...........I think that's safer than a bios upgrade?

Just used one on my new 80 gig drive....only drawback I've found (of course I had to install it on my other drives attached to the same system) is that I can't change my boot drive to one of the other ones now......which I could before....the boot up just hangs on any drive other than the 80 gig master.....


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## Alex Ethridge (Apr 10, 2000)

The drive overlay adds another layer of interpretation of the drive's geometry and is the least stable link in a chain of events that must take place when the OS is reading data from the disk.

Your experience is anecdotal and I'm sure there are thousands of anecdotes that will vary widely from each other; however, having been in the computer service business for several years and seen enough overlay failures to make the fact unquestionable, I know my data is safer without an overlay than it is with one.


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## Lurker1 (Jan 30, 2001)

I think they are about equal. I have used overlays several times and they seem to work fine. They may cause problems when the hard drive messes up and files get corrupted but then I have had problems when the file system gets messed up with normal adressing. 
As for bios upgrades I have done hundreds of them with no problems but they are done on Dells. Dell lets you download a file that creats a floppy disk that has all the upgrade files needed for one model. When you run a Dell bios upgrade it checks the file to make sure that it is complete and that it is the correct one for the unit you want to change. Too bad all manufacturers don't make it so easy.


If you can get a bios upgrade for your system that works for the hard drive I would use that before using a disk overlay. Unfortunately there are many motherboard with no upgrades available. Then a overlay (or IDE controler card) must be used.


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## ~Candy~ (Jan 27, 2001)

Interesting.........thanks for the explanation........since I'm too afraid to try a bios flash, guess I'll just have to live with it....then on the other hand, if the bios flash does go bad, guess I'd just have to buy a newer, faster computer  

Thanks again............


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## Alex Ethridge (Apr 10, 2000)

This particular board has the most recent BIOS. It has no problem reading an 80-Gig drive so the BIOS isn't a problem and an overlay isn't needed in this case.


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## tjsudo (Jul 27, 2000)

Hi,

I found some more information on 15 and 16 heads.

http://www.pcguide.com/ref/hdd/bios/sizeGB394-c.html

Are you still having corrupt name after formatting?

TJ


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## Alex Ethridge (Apr 10, 2000)

Thanks, this seems to explain it in a way someone like me can understand it much better.


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