Avoiding the PCI bottleneck...

[edwardng]

Question! Does the southbridge ATA controller bypass the PCI bus, thereby avoiding the PCI bottleneck of <133MB/s? If this is true, then the dual channel southbridge ATA controller on motherboards should be able up whip out the full 266MB/s of both channels combined at the same time at peak throughput! Anybody in the solid know, please help me with this, as I am quite curious. If it is, then I may buy a cheap ATA controller for PCI and plug my optical drives into it, then use the southbridge controller for a dual-channel WinXP softRAID of four hard drives. I'll use the mobo's included SATA RAID controller for the boot drive.

-Ed

 

[phr0ze]

If I were to guess... You're talking about the MAX2? Either way, where did you read that the PCI bus cant handle the raid to its potential? And if you are talking about getting the best performance, why are you using softRaid?

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phr0Ze

I've been hiding in the shadows @ THG since 97.
AMD1800/768MB/9700Pro/Dragon+/240GigRaid0/DoubleWide with Redundant 350watt

 

[Crashman]

It's probably still restricted as a PCI device. Not that it matters, you would need to RAID at least 3 drives in Level 0 to actually use up 133MB/s, on 3 channels (due to the limits of IDE).

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[edwardng]

For example, the standard 32-bit, 33MHz PCI bus can only handle up to a theoretical 133MB/s. Due to overhead, it's normally much lower, around 100MB/s. If the southbridge controller bypasses the PCI bus, then this under 133MB/s limit is lifted, allowing, as said, up to 266MB/s max throughput (both ATA/133 channels combined). This is important because I do not have a motherboard with 32-bit, 66MHz PCI or 64-bit PCI. If I did, this would not matter. I'm talking about motherboards, any that are restricted to 33MHz, 32-bit PCI and have southbridge ATA controllers. And actually, a quad drive softRAID that skips the PCI bus on my system is faster than a quad drive hardRAID that's PCI bus bottlenecked.

-Ed

-Ed

 

[Crashman]

I already said it's a PCI device. But I also said it shouldn't matter because two drives can't give you more than 133MB/s anyway. In fact, two really good drives in RAID0 will give you around 50MB/s.

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