Resolving BIOS and Drive Size Barriers

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Foreword

Hard drive limitations and barriers can, sometimes, be relatively easy to resolve, while at other times they can be extremely difficult to resolve. The more difficult barriers, at times, require major system component changes, such as replacing an outdated motherboard with a new one. While we have identified most of the limitations and barriers you may face in our segments "Hard Drive Size Limitations and Barriers - The Basics" and "Hard Drive Size Limitations and Barriers - In Depth", you should be aware that as hard drive technology develops, and new larger drives appear in the marketplace, as yet undiscovered limitations and barriers will appear. As these new barriers are identified, we will provide the details here.

The following discusses the more common methods of resolving barriers and limitations, beginning with BIOS issues and upgrades.

BIOS Upgrades

One of the more important methods, and the one most commonly used, to get around the 504 MB barrier is through the use of an enhanced BIOS that supports BIOS translation. Translation allows the BIOS to break the 504 MB barrier by translating between physical disk parameters that the disk understands, and a separate set of parameters that the BIOS understands. The main problem with BIOS translation is that older BIOS's do not support it. Some motherboards support external or flash BIOS upgrades (external meaning that they can be performed away from the manufacturers facilities, such as in a repair shop or your home). A BIOS upgrade can sometimes enable an older system to employ BIOS translation. Most systems that support flash BIOS upgrades can be updated externally to provide Interrupt13 support without even opening up the system case. Most well-known motherboard manufacturers continually offer updated BIOS files, therefore their Web site would be the place to start when considering a BIOS upgrade.

Many of the later size barriers and limitations that you will encounter are due to limitations in BIOS code, therefore they can be similarly overcome by upgrading or flashing the BIOS to a later version that can handle larger drives. All new BIOS's today enable Interrupt13h extensions to overcome the 8 GB size barrier. An upgrade to a current BIOS date will also address other BIOS code problems such as the one that causes the 32 GB size barrier commonly seen in the various Windows versions.

The Best Place To Look for a BIOS Update
The first place to look for a BIOS flash upgrade would be from either the manufacturer of the system or the motherboard manufacturer, and is generally the best solution to a hard disk size barrier problem. Aside from the fact that it is generally free, it has been provided by the original hardware manufacturer. More often than not, it is the simplest and most direct solution to the problem, and once it is done your hard drives will work properly without any further intervention on your part. This solution is far superior to all others that are discussed in this section, and we strongly recommend that you look for a BIOS update before you consider other resolution methods.

Caution: The BIOS on some motherboards cannot be easily upgraded, and is usually do to the fact that either the motherboard has a BIOS chip that is too old to be flash updated, or the manufacturer of the motherboard has decided to no longer support it. While this is common in very old machines, today we frequently find that manufacturers of low-end systems and components (motherboards) discontinue support after as little as two years. There are some alternatives though, when confronted with this problem. In some cases you may be able to purchase a third-party BIOS upgrade, as BIOS code is normally written by one of the top three code developers in the world. This type of BIOS code is considered generic and may not solve (and often does not solve) your problem. Although it is a viable option, it is usually not free, at times costing upwards of $75 or more, and more important, it may not enable all of the features of the motherboard. Another solution, given today's component pricing, and one we fully recommend, is to replace the entire motherboard. Motherboards today can be purchased for little more than it would cost you to purchase a generic BIOS update, and you are assured that the problems you are facing are resolved. You may also want to review the "Alternative Solutions" below.

Alternative Solutions

Enhanced BIOS Expansion Cards
One possible solution to a drive size barrier or limitation that is irresolvable due to a BIOS that cannot be externally upgraded is through the use of an enhanced BIOS expansion card. You might think of it as a BIOS update that comes in the form of an add-on card for your computer. This involves the installation of the expansion card into your system in an available expansion slot and then connecting your hard drives to it. This expansion card replaces your motherboard's IDE/ATA controllers, and the BIOS code on the expansion card takes the place of the hard disk controller code on your systems motherboard. Some controllers will even permit you to continue to use the IDE/ATA connectors on your existing motherboard rather than having to connect them to the controller card itself.

Expansion cards are available in many varieties ranging from very inexpensive, in the neighborhood of $20, to as much as $150. They are available to fit an ISA expansion slot for most older systems that have an extra ISA slot available, as well as in PCI for later model motherboards.

Before we move on, we should add a note of clarification. There two basic types of add-in or add-on cards. One adds only a BIOS chip with new code, thereby permitting you to use the existing IDE/ATA connectors on your motherboard. Another is a complete IDE/ATA controller replacement, which adds both a controller chip as well as the IDE/ATA connectors. The BIOS chip only type of cards, in spite their low cost, have never seemed to be quite as popular as the add-in controller cards that include actual IDE/ATA interface connectors. This is no doubt due to the fact that the add-in cards rely on the existing motherboard controllers and connectors for drive devices, and in some cases the ISA slot requirement for early versions of this type of card. BIOS expansion cards were very popular in the mid-1990s when the first hard disk size barriers began to appear. Now let's take a closer look at a complete controller card.

Upgrading Using a Controller Card
As discussed briefly above, one solution to hard drive size barriers for systems that cannot have their BIOS upgraded, is the purchase and installation of a hard disk controller card. These types of cards completely replace the on-board (on motherboard) IDE/ATA controller hardware of your system, thereby eliminating any BIOS size restrictions associated with the controller. One distinct advantage in doing this, aside from a barrier issue, is that most older systems also have ATA33 transfer rates (the rate at which data is transferred to and from the hard disk). By upgrading to a controller card, you can also increase these transfer rates to ATA66 and ATA100, presuming that your hard drive can support these speeds. You'll find additional information about these speeds and a comparison of them here.

As you may have guessed, these cards differ from BIOS expansion cards in that there is more than just BIOS code in that chip on the add-on card. They are, indeed, a complete controller including the IDE/ATA port connectors. To use them, simply install the card and then attach your hard disk cables that were attached to your motherboards IDE/ATA ports to the new card, add the drivers to the operating system and you're on your way.

These types of expansion cards are more expensive and a bit more complicated than BIOS expansion cards, therefore there are issues that should be examined when selecting one:

Software Translation (Dynamic Drive Overlays)

Before we delve too deeply into Software Translation, otherwise known as "Dynamic Drive Overlays", you should be aware of the fact that we are not a proponent of their use unless there are no alternatives and the need to deploy the large hard drive is immediate. At times, software translation can cause problems for the operating system, data restoration and/or recovery in the vent of a drive crash.

As we have explained earlier, first attempt to overcome the problem by updating the BIOS on the motherboard, and if that isn't an option, regardless of the reason, give adequate consideration to a motherboard or system replacement. No doubt the first thought that will enter your mind is that we are trying to sell motherboards as a solution. True, we sell motherboards, but we also make every attempt to prevent problems that we have seen through our years of experience. The issue comes down to choosing between the alternatives, spending money on a hardware solution, or going with a free software solution. Just keep in mind that free is not always what it implies if doing so wastes considerable amounts of your time and endangers your data. For those of you who can afford to do so, we strongly recommend a hardware solution, such as an expansion BIOS card, add-in disk controller card, third-party BIOS upgrade (for a fee) or a new motherboard.

If a hardware solution is simply not in your future, and you must get your system up and running, then your only alternative in order to access the full hard disk capacity is to use a software translation driver, also referred to as a dynamic drive overlay or DDO. In the past when drive size issues were more prevalent, these drivers were typically named something akin to Disk Manager, EZ-Drive and MaxBlast etcetera. Essentially they, through the use of software, override some of the older BIOS code in the BIOS chip on your motherboard or hard disk controller, thereby  allowing access to the full size of your new hard disk. The software loads immediately during the machines boot up (startup) process and must be active before any other software, such as your operating system, tries to access the disk. To accomplish this, when the DDO is installed the first time, it modifies the master boot record of the boot disk, installing the driver at the very beginning of the disk.

Usually when a new hard disk is purchased at full boxed retail, the drive manufacturer often includes a copy of their driver program, drive overlay and utilities free with the drive. You can also download these drivers and other free disk utilities from the drive manufacturers web site. While there are several of these overlay utilities available, we have seen the least problems with those provided by Maxtor and Western Digital. Both have made an exceptional effort to write premium software and both fully support what they have written.

Maxtor has had one software solution in place since 1993, with its MaxBlast® software. Software translation is an effective, but non-conventional, means of translating sector addresses of large capacity hard disk drives. Instead of loading a driver in the start-up files, MaxBlast® loads drivers before the operating system is loaded. The latest version of MaxBlast® can be obtained directly from Maxtor's Internet Web site. As in the case with Maxtor, Western Digital also has drive translation software to enable the use of large hard drives in systems with an outdated or legacy BIOS, motherboard, and in some cases the operating system itself. Western Digital's version of this software was known as EZ-Drive®, which is now referred to as Western Digital's Data Lifeguard Tools®.

As mentioned at the beginning of this topic, we are not a proponent of using drive overlays. While drive manufacturers often tout that using their software translation drivers is equal to updating the BIOS, simply put, it isn't! There are numerous problems associated with using software translation for large disk support, which supports our position of not recommending them when other alternatives are available. Here are just a few of the more prominent issues:

If you're not doing anything unusual with your computer system such as either multi or dual booting various operating systems, programming, web design or data intensive work, and the potential for data loss is not a concern to you, these overlay drivers will work. Overlay drivers are an acceptable alternative when you need to get your system up and running now and cannot wait for a better solution. If you're concerned about potential data loss, and/or your system has a substantial amount of software to be loaded, we recommend that you seek other alternatives as we have mentioned above.

Reduction Jumpers
Drive size reduction jumpers were, at one time, included on most, if not all, hard drives being manufactured. Today, these jumpers are characterized as a legacy issue and are quickly disappearing. Using the disk size reduction jumpers on some hard drives is a subject rarely touched upon by most technically oriented web sites. While these jumpers are not available on all hard drives, and their use is far from an optimal solution, they are an alternative solution when you need to get yourself out of a problem quickly. Many of the hard disk size barriers we've discussed throughout this particular topic area can cause a system to not identify or even see the hard drive. If the reduction jumpers are on the drive, you can set one or more of them, which then tells the disk to change the drive parameters it presents to the operating system. Since this reduces the size of the drive, the system sees the drive as being small enough to avoid the size barrier, and thus the barrier is avoided. Obviously you lose the capacity of the larger hard drive, but again it is an alternative that you can use to get out of a pressing problem.

Reduction jumpers were originally developed as a method by which system builders could retrofit newer drives into older systems that had a BIOS unable to access the entire drive size. Later, they would be frequently used as a method by which to work around the 4,096 cylinder barrier when it first surfaced. As an example, if you were to install one of the newer hard drives back then, let's say 1.2GB, the BIOS would cause the disk to be seen as an approximate 400 MB. In turn, data would wrap rather than remain contiguous. The reduction jumpers would enable you have the drive report to the operating system that it had less than 4,096 cylinders. Over the last few years, drives that did have these size reduction or capacity limiting jumpers enabled users to work around the 32 GB size barrier by forcing the drive to present a capacity small enough to avoid triggering that capacity barrier.

Obviously the foregoing "solution" is really not a solution at all, but rather a method by which to avoid the consequences of the problem at hand. While it is better than having your system hang when you try to boot, it is still a very poor solution. The reduction jumpers should only be used in conjunction with drive overlay software, and only as a last resort.

Manually Entering Drive Geometry Parameters
Some drive size barrier problems that are associated with older drives, as well as drives that are small by today's standards, can be avoided by simply abandoning the use of the BIOS hard disk auto-detection features and entering the specific drive parameters manually. While we constantly remind users and technicians to use their computers auto-detection features, it should be understood that we are referring to today's technology, not yesterdays. Indeed, auto-detection is the best method to set up hard drives, but this presumes that the BIOS is recent and supports the drives you intend to use.

In some cases, for example, where the data wraps around on the disk when the disk is too large, you can work around the problem by manually entering the maximum parameters that your BIOS can support. Let's suppose for the moment that you had a 540 MB hard disk and that old 486 system of yours is choking on it. The drive has 1048 (logical) cylinders, 16 heads and 63 sectors per track. If you manually set the disk up in your BIOS as having 1023 cylinders, 16 heads and 63 sectors per track, it will probably work fine, but only as a 528 MB disk. This will still provide you with 95-97% of the disk. Unfortunately this work around will be of no help for today's systems with large drives. It will do nothing to get around larger size barriers, such as the 8 GB barrier.

Int 13h Extensions
At the time the 8GB barrier surfaced, the only possible solution was to eliminate the use of the standard Int13h disk access routines. However, in order to accomplish this you had to change or update the BIOS to one that supported what are referred to as Int 13h Extensions. We discuss these extensions here in more detail.

We quickly learned though that merely changing to the Int13h Extensions was not enough, as we had to make changes to everything associated with disk access; the hard disk, the BIOS, and the operating system. Today's operating systems support this transition to how hard disks are addressed. This includes all versions of Windows, beginning with Windows 95 through to Windows XP. It is also important to note that all of today's hard drives support this method of disk addressing. This has allowed us to work around each of the hardware related hard disk barriers, leaving only those caused by the operating system itself. Most of the drive manufacturers mentioned earlier make drive utilities available that you can use to test your system, including its BIOS, and determine if it will natively support Int13h extensions.

With the advent of moving away from the old Int13h and into the Int13h Extensions, we have finally been able to lay to rest the old geometry method of specifying hard disk sizes. In fact, now with the multiple levels of translation available within both the BIOS and the hard disk, logical geometry parameters of IDE/ATA hard disks no longer have any relationship to actual drive characteristics. Even if the setting of geometry parameters were still available, today's newer hard drives, (those at or above 8.4 GB in size), could not be expressed using traditional geometry terms. Today, unlike our recent past, the total number of sectors on the drive is now the key parameter, as is drive access using logical block addressing. To give you an example of what all of this means, a 45 GB drive would, if expressed in conventional geometry, be stated as having 89,355 cylinders, 16 heads and 63 sectors. Today, it is merely referred to as having 90,069,840 data sectors. As an aside, all drives 8.4 GB and over have logical geometry parameters of 16,383 cylinders, 16 heads and 63 sectors, which is why these drives show up as being about 8.4 GB in size if Int13h Extensions have not been implemented.

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