IDE Combined Addressing barrier

 

Different BIOS and IDE Limits

    The original BIOS Int 13h system call passed the Cylinder, Head, Sector (CHS) address directly to the IDE hard drive controller. Which requires accepting the lowest of the limits for each value, causing a capacity limit of 504MB (528 million Bytes).

  BIOS Int 13  
a.k.a. Logical CHS  		IDE (ATA)  
a.k.a. Physical CHS  
Combined Limit
Maximum Cylinders  1024 65536 1024
Maximum Heads  256 16 16
Max. Sectors/track  63 256 63
Maximum Capacity  7.88GB 128GB 504MB

This limitation, and the methods to overcome it, are fully discussed on the EIDE Drives page.

 

Possible Solutions and Work-Arounds:

[WWW Link](Flash) BIOS Upgrades
http://www.pcguide.com/ref/hdd/bios/overBIOS-c.html    [New Window]
 
[WWW Link]Enhanced BIOS Expansion Cards
http://www.pcguide.com/ref/hdd/bios/overCards-c.html    [New Window]
 
[WWW Link]Software Translation Drivers (Dynamic Drive Overlays)
http://www.pcguide.com/ref/hdd/bios/overDDO-c.html    [New Window]
 
 

NOTE: Some SCSI controllers (Adaptec?) Will add Enhanced or Extended Int 13h functions to a system BIOS that does not provide them. And while this is intended for the SCSI drives, these are the same functions that are used by EIDE or ATA drives. (Just be aware that this additional BIOS code may not be loaded if there is no appropriate SCSI device connected to the controller when the system boots.) Otherwise, a product like the Micro Firmware ATA Pro BIOS add-in cards can be used to provide Extended Int 13h functions to a BIOS that does not have them.

 
 
 
Back UP To: Specific Drive Capacity Limits
Next Page: 4096 Cylinder BIOS Barrier
 

 

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Page Content Updated: 9 June 2005