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How onboard "PCI EIDE" ports relate to actual PCI slots

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February 17, 2010 4:58:52 AM

Hi all,

This is part of a question I already posted over in the storage section, and I'm reposting it here (a) because this part is more about motherboard functionality, and (b) because it was buried in a long/detailed post and I don't think it was widely noticed. Either way I'm still looking for an answer.

I am hoping this question applies to any motherboard with PCI slots and onboard PATA controllers, so I'm taking a chance and filing it under "General Motherboard." FWIW, mine is a (rather ancient) Tyan Tiger 100 (http://www.tyan.com/archive/products/html/tiger100.html). It has AGP 2x, five 32-bit/33-MHz PCI slots, and two onboard EIDE ports. I've checked the manual, but it's pretty weak on advanced technical topics.

What's throwing me is that on that Tyan page I linked above, the EIDE ports are referred to as "PCI IDE" and "PCI Bus-Master EIDE Ports." What does the "PCI" part of that mean? More specifically...


1. Given that those EIDE ports are somehow "PCI" in nature, does that mean they are on the same bus as my five PCI slots, and would therefore compete for a chunk of the same 133-MB/sec bandwidth those five slots share? Or does it simply mean they interface with the CPU through a mechanism similar to that used by the PCI slots, but wouldn't touch the slots' bandwidth space?


2. When those EIDE ports are actively mastering the bus, would my bus mastering PCI cards be locked out? (In particular, my PCI SATA card.) Or would the EIDE ports function independently of the PCI slots' bus, and therefore not interfere?


3. Stepping back a little, is it true that my five PCI slots are all sharing one 133-MB/sec bandwidth space to begin with? Tyan support told me slots 4 & 5 are "tied together," but I'm wondering if that's just IRQ sharing and not about bus bandwidth ... of course IRQ sharing is a whole other can of worms...


The reason I'm researching all this is I'm planning to add a second drive for data/documents. My main (and currently only) drive is a VelociRaptor, which alone can pretty much saturate the PCI bus and no doubt keeps my SATA card pretty busy. As such, while I could add another SATA drive, instead I'm leaning towards getting a PATA drive. I don't really need it to be that fast, and I'd rather not get in the VelociRaptor's way (I mean, would you? All those teeth and claws and such...). But this strategy really only makes sense if the onboard EIDE ports don't compete for the PCI slots' bandwidth.

I called Tyan support, and they told me the EIDE slots don't compete for PCI bandwidth, but they seemed a bit confused about some aspects of this old board, so I'm seeking additional opinions/confirmation.
a b V Motherboard
February 17, 2010 2:45:33 PM

Okay, very quickly PCI does not pertain to anything specifically.
It stands for "Peripheral Component Interface" of which their are many types.
I am in the office and don't have time to go into this at the moment....sorry! Maybe later this evening.
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February 17, 2010 10:30:15 PM

Ah, thank you ... so in case you have a chance to go into this in greater depth later ... does this means that in spite of being PCI, my EIDE ports would not compete for the 133-MB/sec bandwidth shared by my five PCI slots (assuming that's a correct assessment of those slots' bandwidth)? And that those EIDE ports' bus mastering capability would not conflict with bus access for any of my PCI cards that are also capable of bus mastering?
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