Word of caution for nForce chipset mobo's and PCI cards

[Jon P. Inghram]

My old SBLive! wouldn't work properly in the second PCI slot; It would detect the presence of a "multimedia card" but the drivers wouldn't recognize it as an SBLive! and would refuse to install. It seemed to work fine in the third slot but then it shared an IRQ with my PCI-Express video card.

Out of frustration and curiosity I tried my 3C 905B in the PCI slots with surprising results: while the card was recognized in the second slot and the drivers installed properly, the system BSODed a few moments later. The results were the same in the third slot where the SBLive! had just been working fine a short while ago. Finally I tried a USB 2.0 expansion card, which worked perfectly fine in both slots!

After digging around on the net I discovered a fascinating little tidbit of info: If you run the nVidia nTune utility it'll complain about the PCI bus tracking the HT bus and that it might result in problems if you o/c your system. Well, it turns out that when the HT bus is running at it's default speed the PCI bus gets overclocked FAR out of spec, with only a few cards being able to handle the high clock. Here's the kicker... the solution is to overclock the bus a slight amount, 1 MHz for example. This will cause the chipset to free the PCI bus from the HT bus and allow it to run at 33.33 MHz!

[schmosef]

This is going to sound dumb but... What's the HT bus?

[Jon P. Inghram]

Dang, everybody knows what the HT bus is, have you been living in a cave or something?

http://en.wikipedia.org/wiki/Hypertransport

It's an AMD thing, not to be confused with Intel's HT, which in their case means Hyper Threading, the pseudo-dual-core thing P4's typically have.

[schmosef]

Ok, I guess I have that then. I don't have any add-on PCI devices so I've not run into this problem. Thanks for the info.

[rylan]

Sounds more like a bug in how the BIOS is implementing the multipliers and bus clock selection.
That would be a pretty big design error if it runs the PCI bus out of spec at default HT speed.

[Gurm]

This is only a small subset of these boards.

[Jon P. Inghram]

Yeah, it's not the chipsets fault, a crummy BIOS is always a good way to cripple an otherwise good board, although I would have figured Asus wouldn't have screwed up that bad. Back in the K6 days I had an Epox board that was supposed to support whatever the fastest UDMA mode was back then, but it didn't actually work until enough people complained about it to them.

[Liquid Snake]

Which Asus motherboard were you using?

[Jon P. Inghram]

I'm using an K8N4-E Deluxe now, up from a TUSL2-C.

[Liquid Snake]

Hm. I've used a few Asus boards and while they are generally good, all of the ones I've worked with have had some BIOS-related issues - some minor, some major (like this one with the PCI bus).

[Gurm]

ASUS is pretty "focused" in certain areas, somewhat blinding their engineers to certain OTHER problems.

For example, my current board is an A7N8X-E Deluxe. It supports, according to the BIOS, up to 15x multiplier. HOWEVER, you can't actually PICK anything above 12x. If you pick 13x, the BIOS sets itself back down to a substantially lower number. Why? They skimped on how many bits to use, figuring EVERYONE with a fast chip would auto-detect the multiplier. Grr... makes this Mobile Athlon less than entirely useful, since I can't select 166x14 or anything like that. Gotta go for 200x12, which isn't QUITE doable... or settle for a lower speed.

But otherwise it's a great board. They just... overlooked that part.

[Wombat]

ASUS is pretty "focused" in certain areas, somewhat blinding their engineers to certain OTHER problems.

For example, my current board is an A7N8X-E Deluxe. It supports, according to the BIOS, up to 15x multiplier. HOWEVER, you can't actually PICK anything above 12x. If you pick 13x, the BIOS sets itself back down to a substantially lower number. Why? They skimped on how many bits to use, figuring EVERYONE with a fast chip would auto-detect the multiplier. Grr... makes this Mobile Athlon less than entirely useful, since I can't select 166x14 or anything like that. Gotta go for 200x12, which isn't QUITE doable... or settle for a lower speed.

But otherwise it's a great board. They just... overlooked that part.

Can't you wire up the socket yourself?