What does he need to do this? Flashcards FlashCards Essays. Create Flashcards. Share This Flashcard Set Close. Please sign in to share these flashcards. We'll bring you back here when you are done. Sign in Don't have an account? Set the Language Close. Add to Folders Close. Please sign in to add to folders. Upgrade to Cram Premium Close. Upgrade Cancel. Raspberry Pi Essay The fact of missing clock can be worked rounded using a network time server, and most operating systems do this automatically.
The Digital Divide Research Paper Sounds like a great idea in theory to bridge this gap and really it is something that should be more thoroughly worked on, but instead it is being used as a Shuffle Toggle On. Card Range To Study through. What is the maximum size hard drive it can support? Additionally, any new feature introduced is also found in all future releases.
The interface only worked with hard disks at first. Eventually, an extended standard came to work with a variety of other devices -- generally those using removable media. Figure 7. The relationship between BIOS and physical sector addressing. The original BIOS-based driver for hard disks is accessed via software interrupt 13h 13 hex and offers functions for reading and writing drives at the sector level. Standard INT13h functions require that a particular sector be addressed by its cylinder, head, and sector location—otherwise known as CHS addressing.
This interface is used by the operating system and low-level disk utilities to access the drive. This interface used numbers to define the particular cylinder, head, and sector being addressed. The concept of a maximum value given a number of digits is simple: If you had, for example, a hotel with two-digit decimal room numbers, you could have only 10 2 rooms, numbered 0— Because the head is identified by an 8-bit number, the maximum number of heads is 2 8 , numbered 0— Finally, with sectors per track there is a minor difference.
Sectors on a track are identified by a 6-bit number, which would normally allow a maximum of 64 2 6 sectors; however, because sectors are numbered starting with 1 instead of 0 , the range is limited to 1—63, which means a total of 63 sectors per track is the maximum the BIOS can handle.
Using the maximum numbers possible for CHS at the BIOS level, you can address a drive with 1, cylinders, heads, and 63 sectors per track. Because each sector is bytes, the math works out as follows:. Limits also exist in the ATA interface. As you can see, the lowest common denominator of the combined CHS limits results in maximum usable parameters of 1, cylinders, 16 heads, and 63 sectors, which results in a maximum drive capacity of MB. This became known as the MB barrier also called the MiB barrier , and it affects virtually all PCs built in or earlier.
But by , drive technology had developed such that making drives larger than what the combined BIOS and ATA limitations could address was possible.
Clearly a fix for the problem was needed. These include the following:. In an effort to make its methods standard among the entire PC industry, Phoenix released the EDD document publicly and allowed the technology to be used free of charge, even among its competitors such as AMI and Award. The fix involved what is termed parameter translation at the BIOS level, which adapted or translated the cylinder, head, and sector numbers to fit within the allowable BIOS parameters.
These refer to the different mathematical methods of doing essentially the same thing: converting one set of CHS numbers to another. CHS bit-shift translation manipulates the cylinder and head numbers but does not change the sector number.
It begins with the physical drive reported cylinders and heads and, using some simple division and multiplication, comes up with altered numbers for the cylinders and heads. The sectors-per-track value is not translated and is passed unaltered.
The term bit-shift is used because the division and multiplication math is actually done in the BIOS software by shifting bits in the CHS address. CHS bit-shift translation is based on dividing the physical cylinder count by a power of 2 to bring it under the 1, cylinder BIOS INT13h limit and then multiplying the heads by the same power of 2, leaving the sector count unchanged. The power of 2 used depends on the cylinder count, as indicated in Table 7. This example shows a drive with 8, cylinders and 16 heads.
In this case, it would divide by 8, which results in a new logical cylinder count of 1,—which is below the 1, maximum. Because the cylinder count is divided by 8, the head count is then multiplied by the same number, resulting in logical heads, which is also below the limit the BIOS can handle. So, although the drive reports having 8, cylinders and 16 heads, the BIOS and all software including the operating system instead see the drive as having 1, cylinders and heads.
The result is that by using the logical parameters, the BIOS can see the entire 4. The BIOS does the rest of the work for you. To solve this, an addendum was added to the ATA-2 specification to specifically require drives to report certain ranges of geometries to allow bit-shift translation to work.
Thus, all drives that conform to the ATA-2 specification or higher can be translated using this method. Combined with the standard head and sector limits, this resulted in the inability to support any drives over 2.
Even so, some problems still existed with bit-shift translation. This was a problem for drives larger than 4. Any BIOS that implemented this scheme essentially had a 4. Note that this was not a problem for Windows NT or later.
The number causes a problem because equals b, which takes 9 bits to store. The value which equals b is the largest value that can fit in an 8-bit binary register and is therefore the maximum number of heads those operating systems can support. These adjusted cylinder and head values would then be translated. The following example shows the results:. As you can see from this example, a drive with 12, cylinders and 16 heads translates to cylinders and heads using the standard CHS bit-shift scheme.
Then, the new cylinder value is CHS bit-shift-translated it is divided by 16 , resulting in logical cylinders. Likewise, the 15 heads are multiplied by 16, resulting in logical heads. If the logical cylinder count calculates to more than 1,, it is truncated to 1, The following shows a more typical example in the real world.
Several 8. For those drives, the translations would work out as follows:. Note that the revised CHS bit-shift translation rules result in supporting only 7. In fact, the parameters shown with heads are the absolute maximum that revised CHS bit-shift supports.
Fortunately, another translation mode is available that improves this situation. The LBA-assist translation method places no artificial limits on the reported drive geometries, but it works only on drives that support LBA addressing at the ATA interface level. LBA-assist translation fixes the sectors at 63 no matter what and divides and multiplies the cylinders and heads by predetermined values depending on the total number of sectors. This should always be true if the drive reports 63 sectors per track and 4, 8, or 16 heads.
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