I was on the fence about whether to submit this under the hard disk or motherboard category, as it's a little of both. Sorry about the length -- it's a somewhat detailed/complicated question.
I'm considering adding a second drive for data/documents, but I'm seeking clarification on a few technical details. First, relevant specs:
Motherboard: Tyan Tiger 100 (don't laugh, I know it's old)
CPU: dual Pentium III @ 600 MHz (yes, I know, old old old)
Expansion bus: 32-bit PCI @ 33 MHz
System drive: WD Velociraptor (on Promise SATA 3.0 Gb/s PCI card)
Yes, I could simply add another SATA drive to the Promise card. However, given that the Velociraptor alone is nearly fast enough to saturate the PCI bus, I'm leaning towards getting WD's 500-GB PATA drive and connecting it to one of the motherboard's EIDE ports (UDMA/33) instead.
My rationale is that for a data/documents drive, I really don't need the speed of SATA (or even a faster UltraDMA mode), and I'd rather let my fast system drive keep its free reign over the SATA card and PCI bus (along with some lesser competition from a network card and a USB card, but what are ya gonna do). What I'm wondering, however, is if that's how it would really work. (Oh, and I'm assuming the UDMA/100 WD will sync down to UDMA/33 mode without difficulty...)
The motherboard specs (http://www.tyan.com/archive/products/html/tiger100.html) describe the drive controllers as "Two UltraDMA/33 PCI Bus-Master EIDE Ports." Hmm, they're PCI? Does that mean they're on the same bus as my PCI slots and would share the same 133 MB/sec bandwidth with those slots, thereby defeating my whole purpose?
From the documentation, I am pretty sure I have at least two PCI buses (one is for AGP), so maybe the EIDE ports are their "own thing" too, but the documentation is not helpful on that point.
I called Tyan support, and they said the EIDE ports do NOT compete for bandwidth with the PCI slots. But some of the things they told me sounded a bit dubious and made me wonder if their own internal documentation for such an old board might be a little fuzzy.
For instance, they said PCI slots 4 and 5 are "tied together," and I don't know if that means bandwidth or IRQ sharing or something else, but the BIOS IRQ priority settings seem to group slots 1 & 5, not 4 & 5. This discrepancy is confusing. Further, I've read that AGP usually shares an IRQ with PCI slot 1, but according to Device Manager, right now my AGP card is sharing an IRQ with the cards in slots 3 and 4 (unless those numbers are meaningless artifacts of ACPI). In any case, I'm getting a lot of conflicting information about how my board's resources and bandwidth are divided up, and as such I'm really not sure how best to distribute my hardware internally. I'm *assuming* slots 1 through 3 don't each have their own 133-MB/sec bandwidth, while slots 4 and 5, being "tied together," share another 133-MB/sec bandwidth -- I don't *think* that's how it works, at least. (If anybody has any input/clarification on any of the above, I'd be glad to hear it.)
Given all that, the bottom line is: if OS/apps drive performance is my top priority, am I better off adding a PATA drive for data/documents to the onboard port versus adding another SATA drive to the PCI card, which already has its hands full with a super-fast drive?
Second part of question: I believe my BIOS has a 32-GB drive limit, and I'm aware that Windows XP prior to SP2 has the 137-GB limit. WinXP setup recognizes my entire 300-GB Velociraptor, of course, since it's on the Promise card and I load the drivers from floppy during setup. Assuming I'm understanding correctly, if I add the 500-GB PATA as a data/documents drive and reformat/reinstall Windows at some point in the future, the worst case scenario is that I won't be able to access my data/documents drive until I reach the SP2 portion of the process (assuming I don't use an SP2 setup CD or slipstream one myself). The BIOS 32-GB limitation shouldn't affect this, right? Because if I understand correctly, XP bypasses the BIOS anyway, and I'd care about the BIOS only if I was using something like DOS. Then the only problem would be that I might need to rearrange drive letters once SP2 is installed and Windows suddenly finds the 500-GB drive. Is this all correct?
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I'm not sure about the BIOS limit thing, since I was like 8 in 1995. So no personal experience there.
But for the bus thing, it would be best to try and have the ethernet on one bus and the SATA on the other. If you ever use network for files locally, it would quickly hit the limit and plateau at 10 MB/s. (I've done it using a SATA card like that and using a regular P3 system as a server for a bit)
As such it would be best to use the PATA plug for that other drive. The only issue I could see is that it may be hit by that BIOS limit (which like I said I don't really know) because that would be straight off of the motherboard, whereas the velociraptor is likely shielded because the PCI card does all the real handling.
Yeah, I just wish the documentation was clearer on how the various PCI slots share resources. As it is, I don't know which slots I should avoid using simultaneously. If I trust Tyan tech support, it's slots 4 & 5. If I assume the BIOS IRQ priority settings imply something about PCI slot pairing, however, it's 1 & 5. Then there's the whole thing about "AGP often shares an IRQ with PCI slot 1" that's mentioned all over the Internet, but not in my documentation.
Plus I don't know for sure if the onboard EIDE ports ("integrated dual channel PCI IDE," according to the product brief) eat into the same bandwidth shared by my PCI slots, although the Tyan tech said they don't. If that's correct, then I'm definitely better off using an EIDE port for my second drive. But that's an "if." (Why don't I necessarily trust Tyan on this? Because the board is so old, and because they gave me seemingly contradictory information on the PCI slot pairing issue.) I guess, if nothing else, I can hope that it gives the SATA card less work to do if I choose onboard PATA for my second drive.
I think, from what I've read, that I might be able to figure out the slot resource sharing deal if I do a fresh system build with ACPI disabled (so the IRQs that show up in Device Manager are "honest," if I understand correctly) and then experiment with moving cards around. But man, what a pain. And I'm not even sure if that approach will really clear up the mystery. I'm just basing that theory on a bunch of Googling. *shrug*
If it's possibly 4 and 5 or 1 and 5 the solution is simple. SATA on 5, nothing in 1, ethernet in 3. It doesn't matter where less often/low bandwidth things like the modem go. Then you just need to see if the BIOS size limit really is a limit for the drive that you would add to the PATA plug.
That's basically what I was thinking, although then I have to figure out where to put my USB card, especially since it seems to share IRQs all over the damn place (it's currently using 16, 18, and 19). But according to at least one thing I read recently, crazy IRQ sharing is just something USB does. So maybe one can't avoid that. (I've seen conflicting info on whether IRQ sharing hurts performance, so if in doubt, I'd rather avoid it if possible.)
Plus right now, my AGP card is sharing an IRQ with both USB and my SATA card (currently in PCI slot 4). Is that weird or what? That strikes me as a bad thing for AGP and SATA to share. Granted, if what I read recently is true, IRQ assignments in Device Manager should not be taken literally when ACPI is enabled, but I dunno if that's true. But one thing's for sure: I am finding it rather difficult to find any consistent information on slot resource sharing and such.
Probably some experimentation is in order, along with card arrangement such as that which you suggested. I'm leaning towards giving the PATA drive a shot. I feel like the BIOS drive limits shouldn't affect XP based on what I've been reading. Guess I'll find out.