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cobolfingaz
n00b
Joined: 18 Sep 2005
Posts: 9
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 Posted: Mon Jan 09, 2006 8:51 pm Post subject: hdparm question. |
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as in the man page :
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"Query/enable (E)IDE 32-bit I/O support. A numeric parameter can be used to enable/disable 32-bit I/O support: Currently supported values include 0 to disable 32-bit I/O support, 1 to enable 32-bit data transfers, and 3 to enable 32-bit data transfers with a special sync sequence required by many chipsets. The value 3 works with nearly all 32-bit IDE chipsets, but incurs slightly more overhead. Note that "32-bit" refers to data transfers across a PCI or VLB bus to the interface card only; all (E)IDE drives still have only a 16-bit connection over the ribbon cable from the interface card."
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i have four ide disks in the two main motherboard channels, and an additionnal one from a promise card.
i don't understand what "data transfers across a PCI or VLB bus to the interface card ONLY". can anybody explain?
how 32 bit I/O support work as opposed to 16 bit support in my case?
can I turn on 32 bit I/O support on my disks?
thanks in advance for your help,
best regards. |
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vladgrigorescu
Guru
Joined: 11 Jan 2005
Posts: 360
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| Posted: Tue Jan 10, 2006 12:21 am Post subject: |
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| Be careful with hdparm. If you don't understand an option, than it might be a better idea to not try it out, as it can seriously b0rk your drives. Or, check out some high-performance "safe" hdparm settings on here and other sites. |
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nomorecoolnames
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Joined: 10 Jan 2005
Posts: 69
Location: Tennessee
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| Posted: Tue Jan 10, 2006 12:38 am Post subject: |
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Hello cobolfingaz.
| Quote: | | i don't understand what "data transfers across a PCI or VLB bus to the interface card ONLY". can anybody explain? |
I think that the man page is telling you that the data transfer from the bus on the motherboard to the addon card will be 32 bit, but the transfer from the card to the drive itself will be 16 bit only.
| Quote: | | how 32 bit I/O support work as opposed to 16 bit support in my case? |
This is talking about the word length that the bus is capable of transferring at a time. A 32 bit bus can transfer 4 characters compared to 2 characters on the 16 bit bus. The 16 bit bus is like having a 2 seat car and the 32 bit bus is like a four seat car. If eight people wanted to go somewhere you would have to make 4 trips on the 16 bit bus compared to 2 trips on the 32 bit bus.
| Quote: | | can I turn on 32 bit I/O support on my disks |
I would say that that depends on your motherboard, hard drives, and probably the ribbon cables that you are using. My old PIII ( i just checked after reading this post) with a brand new ide hard drive is running in 16 bit mode. But my 64bit system with a brand new ide hard drive is running in 32 bit mode. Perhaps someone with more knowledge than I can provide us with the answer that one. 
Last edited by nomorecoolnames on Tue Jan 10, 2006 3:29 am; edited 1 time in total |
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bollucks
l33t
Joined: 27 Oct 2004
Posts: 606
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| Posted: Tue Jan 10, 2006 2:52 am Post subject: |
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| If proper chipset based DMA support is being used by your IDE driver then these other options are meaningless as they only affect PIO transfers. |
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nomorecoolnames
n00b
Joined: 10 Jan 2005
Posts: 69
Location: Tennessee
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| Posted: Tue Jan 10, 2006 3:25 am Post subject: |
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| Quote: | | If proper chipset based DMA support is being used by your IDE driver then these other options are meaningless as they only affect PIO transfers. |
Direct Memory Access routes data from your hard drive to the IDE interface to your memory and vice versa. Programmed I/O also requires the CPU to be involved. DMA is a more efficient way of utilizing the bus. If you double the size of the bus from the IDE interface to the memory then you can send more data in one trip. Enabling 32 bit IDE access should cause the IDE interface to bundle two 16 bit groups of data together and then transport them to and from the memory together. You should receive a small increase in efficiency, but nothing to get excited about because of the 16 bit bottleneck between hard drive and IDE interface. |
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bollucks
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Joined: 27 Oct 2004
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nomorecoolnames
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Joined: 10 Jan 2005
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Location: Tennessee
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