The MFT contains the partition information. The BIOS limitation as a hard-coded limit would prevent booting to anything beyond that limit, but Windows doesn't care what the BIOS says, honestly. Once Windows has taken over operational control of the computer system, it uses its own drivers and tables to deal with the hardware. The BIOS is only there to get everything started and powered on and to hand off control to the Operating System.

Case in point, let me tell you about my laptop. It's a Dell Inspiron XPS Gen 2 that I bought directly from Dell in 2005 via a military discount (I had just joined the U.S. Army and had until 2011 to go). It came with an 80GB PATA 2.5" HDD. And with Windows XP, you'd get as expected a single NTFS 80GB partition for the whole thing.

Well, this being a gaming PC, 80GB simply wasn't enough storage space, so I went out and bought a 2.5" PATA 250GB HDD. The BIOS reports a 137GB drive...because that's the most the BIOS can see/use. But for some reason, I can see this 250GB drive, write to it, read from it, etc. So I installed Windows XP on it.

And it worked.....for about 6 months.

At some point during a Windows Update install, the system had to reboot and from that point on, it would REFUSE to boot. Period. The system would lock up on a black screen with a blinking underline cursor in the top-left of the screen and nothing would happen. No HDD activity, nothing. Using a CD-ROM Boot utility, I can see the data still on the HDD. All of the files are there. But it's not booting. Nothing short of a wipe and reinstall of Windows XP from scratch solved anything.

Then it happened again...roughly 4-6 months later. Same shit. Had to wipe and reload.

As it turns out, the solution to this problem was very simple once I came to understand the nature of the problem. Running past a certain Windows Update caused the system to write one or more NECESSARY files for Windows XP to boot to be BEYOND the 137GB space limit. Once there, the BIOS was unable to access that section, so Windows would fail to boot at that point. Windows XP hadn't installed to the point where it could handle the extended area of the drive itself. It was still relying on the BIOS to pull the data from the drive during the boot process.

So what was my fix? Well, to forbid Windows from being anywhere past that point. So what I did was on the final wipe and load, I created TWO partitions: a 40GB NTFS partition at the beginning of the drive for C:, called it "Windows", and set it to hold Windows XP in its entirety. Then I formatted the remaining ~200GB into a D: in NTFS as well and called it "DATA". All of my games, profile folders, etc. are on the D: taking up THAT space. So I get all of the advantages of storing more games and more programs without having to worry about Windows XP not booting because of that stupid BIOS 137GB drive limitation. And I've never had a problem since. The system has been 100% stable for almost 7 years now. I did the final install back in early 2010.

So I will say that since your bootloader for both DOS and Windows 95 are contained in the very beginning of the drive in the first 8GB partition, I think this is why everything is working properly. Windows 95's tables work for Windows 95 (which is why DOS can't see the extended partition or even use it) and DOS actually DOES use the BIOS interface, hence the 8GB partition being usable and not being able to even see the extended partition.

Does that help you?

I think this is exactly the answer I was looking for; thanks for sharing!

Your anecdote about what happened after the Windoes update is kind of what I was expecting to happen right away without the DDO, but given that Windows uses its own non-BIOS means to access the disk, it makes more sense that it would work the way it is. It seems I have incidentally and inadvertently already implemented what the proper solution is in this case, as you solved your problem, to have the bootable OS partition entirely below the 8GB barrier, and then whatever else beyond that doesn't matter.

I'm curious if Windows or its installer would let me partition the disks sort of how I have it now with the partitions that were created by the DDO installer; that is, create a 2GB (or so) primary partition for boot and the OS and then allocate the rest of the disk (beyond 8GB) for a data partition. Not sure on that though, as fdisk in my Windows install displays the drive size as 8GB so might not let you create a partition beyond that reported side. Not sure if theres another partition utility within (or available for) Windows that would ignore that...

I have another 20GB Seagate drive lying around, I might experiment with this if I get ambitious.

RJDog wrote:

Not sure on that though, as fdisk in my Windows install displays the drive size as 8GB so might not let you create a partition beyond that reported side. Not sure if theres another partition utility within (or available for) Windows that would ignore that...

I can tell you that some versions of fdisk included with Windows had major problems with large drives. You might want to ensure you have a fixed version.

I have version 3.2 of the PCCHIPS M571 and with the latest patched bios installed it natively supports up to 32GB HDD.
It's packed away at the moment but I was using a 40GB drive that had been partitioned and formatted in another computer.
Simply by altering numbers in the bios I got it up to 40GB and it worked in dos and windows no problems at all without any
overlay or other software installed. Just do not run an auto setup in the bios for the hdd as it will cause it to not be identified.

copied from this website http://m571.com/m571/m571upgrade.htm
"A fast hard disk really wakes up a system. Research which hard disks perform well. Make sure to get a 7200 rpm unit or better and insist on drives that have a 2 MB buffer. Even though the M571 is limited to 33 MHz ATA data transfers, there is a noticeable increase in performance with a faster disk. If a disk larger than 8.4 GB is used, you must install the 4/21/99 BIOS image. (This also applies to USB capability, by the way!) This BIOS release will support disks up to 32 GB. Do not use SiS IDE drivers! Use the Microsoft drivers provided with Win 95 OSR 2, Win 98, or a later OS. The Microsoft drivers will have a DMA box in the HDD Device Manager entry under settings (Win 9x/ME only), which should be checked. Enabling DMA will give you noticeably faster hard disk access times."

Imperious wrote:

I have version 3.2 of the PCCHIPS M571 and with the latest patched bios installed it natively supports up to 32GB HDD. It's pac […]
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I have version 3.2 of the PCCHIPS M571 and with the latest patched bios installed it natively supports up to 32GB HDD.
It's packed away at the moment but I was using a 40GB drive that had been partitioned and formatted in another computer.
Simply by altering numbers in the bios I got it up to 40GB and it worked in dos and windows no problems at all without any
overlay or other software installed. Just do not run an auto setup in the bios for the hdd as it will cause it to not be identified.

Yay thats what I have! (3.2A actually) I have had absolutely no luck in upgrading the BIOS past its stock firmware that supports 8GB. But I think this inadvertent experiment has shown that it is possible to use a drive that is formatted outside of the motherboard that only supports 8GB, just as you mentioned. I am going to have to experiment with changing the CHS values in the BIOS as you suggest.

Imperious wrote:

Do not use SiS IDE drivers! Use the Microsoft drivers provided with Win 95 OSR 2, Win 98, or a later OS. The Microsoft drivers will have a DMA box in the HDD Device Manager entry under settings (Win 9x/ME only), which should be checked. Enabling DMA will give you noticeably faster hard disk access times."

I've been through Timmy's M571 site a bit, and I guess I missed this. Good thing I kept using the default Windows drivers rather than loading thr SiS drivers... I have them downloaded but I've been lazy lately.