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Discussion Starter · #1 ·
I have an old Dell box that is still serving me well:


PII-450

Intel 440bx

Promise Ultra100 TX2 w/2 WD2000JB 200GB, 8MB cache drives

crap ATA-33 system drive


Each 200GB drive can hit 56MB/s (according to Winbench99's transfer rate test) on my setup.


But when I have them striped (RAID 0) with Win2k software RAID, the transfer rate is clamped to about 60MB/s across the entire array. I'm not sure if my PCI bus is 33MHz or 66MHz, but even at 33 the theorhetical limit is 125MB/s. I don't expect to reach that limit, but 60MB/s just doesn't sound right to me.


I'm wondering if there's some other built-in limit that I'm not realizing. I'm pretty sure I've seen higher bandwidths reported on other BX boards - maybe something about Dell's OEM board? Or hopefully there's some configuration setting that I totally missed.


Any ideas?
 

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Discussion Starter · #3 ·
Yes. The RAID drives are on separate cables connecting to the TX2's 2 IDE channels. Both drives are configured in "Master/Single" mode (meaning there's no slave present).


I've heard that this card shares interrupt requests between its 2 IDE channels and that, in theory, that limits throughput. Personally, I don't believe this is true, or at least I don't think it matters. If it did, I think there'd be more of a stink about it. I've been trolling the Web and haven't found any complaints about the card's bandwidth.


But... When I get home I'll try putting one of the RAID drives on my mobo's secondary channel to see if it runs any faster.
 

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Discussion Starter · #4 ·
Actually... my test won't work at all. I think my mobo's IDE channels only support ATA-33, ATA-66 at best.


My test will have to be more hard core. I have a 2nd Ultra100 TX2 that I can pop in. Building a RAID 0 with one drive per TX2 should reveal if the limit is in the TX2 cards or elsewhere.
 

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You bx board would be 33mhz, which is pretty normal for most 440bx motherboards. However, I don't think that is your bottleneck. Most likely you're motherboard has ATA-33 (33MB/s transfer) IDE channels. 2 x 33MB/s is maxing out at around 60MB/s. Keep in mind that the 33MB/s number is theoretical maximum, there's ECC and other overhead that will prevent you for getting that sustained 33MB/s.


If your motherboard has ATA66 then it might be some other issue. Some hard drives have been known to perform poorly in raid-0 (older seagate barracuda drives).


Pop in your Ultra 100Tx-2, that should give you a boost in your transfer rates.
 

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Discussion Starter · #6 ·
well just to clarify - my 60MB/s limit was reached when both drives were connected to the Utra100 TX2 (which is ATA-100).


They were never connected to the mobo's slower ATA-33 IDE channels.


Now I'm assuming that an ATA-100 PCI add-on card can still operate at ATA-100, even when the mobo's built-in IDE interface is only ATA-33. Since the 200GB drives could each reach 56MB/s before they were striped, this assumption seems to be true (otherwise a single drive would top out around 33MB/s).
 

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Discussion Starter · #7 ·
SUCCESS!!


Using TWO Ultra100 TX2 cards w/one drive on each card I was able to hit the following numbers:


Winbench 99:

transfer rate beginning: 80MB/s!!

transfer rate end: 60MB/s

transfer rate peak: 97MB/s!

(for some reason the highest rate was in the middle of the RAID 0 array. I'm guessing the PCI bus was just noisy until it settled down near the middle of the test).


This is more like it. Tom's Hardware Guide guesstimates that you'll only be able to hit 2/3 of your available PCI bandwidth. With my 32-bit, 33MHz bus that gives us:


(32bits * 33,000,000/s) / (8bits/Byte) * (2/3) / (1024B/kB) / (1024kB/MB) = 84MB/s


So my results are right in line with that guesstimate.


It must have been the BIOS and/or PCI slot that was limiting the Ultra100 TX2 to 60MB/s. This card on newer mobos has definitely blown past that number.


The remaining question is: Is there any way to unlock that 60MB/s barrier for a single PCI card on this old mobo?
 
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