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IDE Addressing Limit

U

Uuplaku

Member
Now, its well known that the maximum size that an IDE hard drive can address is 137 GB's. My question is: How are these drive manufacturers able to come out with these 160GB drives if the maximum spec is only 137?! Do they do it through BIOS tricks (like they did to get older IDE drives to run past 500mb)? This is truly bizarre.
 
As far as I know the largest IDE drive is 120GB, there are 180GB drives that are SCSI. Some companies might be selling systems with two 80GB drives in RAID 0.
 
They sell you a controller with it, most (if not all) ATA/133 controllers also come with an update that uses 48-bit addressing which goes way past 137G.
 
Well, Maxtor recently announced their brand new 160gb hard drive. SCSI doesnt suffer from the same limitations as IDE drives because its a different spec. The current spec for ATA addressing is a 28-bit system, allowing for a maximum capacity of 137.4gb. I was wondering how Maxtor was able to break that barrier.
 
The ATA133 specification incorporates 48-bit addressing that allows hard drives greater than 127GB.
 
Oh please Andy ... don't YOU start mixing that stuff up as well.

ATA is the specification document.
UDMA is a transfer method defined within this spec.
LBA is a sector addressing method defined within this spec.

Revision 6 of the ATA specification defines 48-bit LBA addressing as an extension of the drive internal controller's command set. Previous LBA was using 28-bit sector numbers, allowing 128 real GBytes (137 billion bytes) to be addressed with 512-byte sectors.

UDMA mode 6 aka UDMA-133 or even worse ATA-133 is NOTHING to do with that. It's just coincidence that all the new drives that exceed the 128-GByte limit using LBA-48 happen to have UDMA mode 6 as well. But neither on the drive nor on the system side is UDMA mode 6 capability required for LBA-48. If you desperately want to, you can do LBA-48 on an ancient ISA IDE adapter.

SCSI btw uses 32-bit sector numbers and can use larger sectors than 512-byte too, so we'll hit the ceiling there at 2 Terabytes per drive or later.

regards, Peter
 
Oh please Andy ... don't YOU start mixing that stuff up as well.

I believe his point was that even though UDMA 6 and LBA-48 are seperate entities, (nearly?) all LBA-48 enabled adapters are also UDMA-6. Meaning you can't buy a UDMA-4 controller with LBA-48 bit addressing, so it's pointless to seperate them (unless you're writing drivers for them, then you might want to)
 
them being separate entities is not at all pointless ... just figure how many people have UDMA mode 4 or 5 capable mainboard integrated IDE bridges
and might want to use those huge HDDs. The message to all these people is to look for a $0 BIOS update, not a $50 or more controller card.

regards, Peter
 
Ugh...sorry Peter....I posted that at 5am in the morning without sleeping....😱
 
them being separate entities is not at all pointless ... just figure how many people have UDMA mode 4 or 5 capable mainboard integrated IDE bridges
and might want to use those huge HDDs. The message to all these people is to look for a $0 BIOS update, not a $50 or more controller card.


You're right, I didn't think of it like that. Have any motherboard or IDE controller manufacturers released BIOS updates for this yet?
 
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