[Ask r/hardware] Questions about the 890fx and 890gx mobos. E.g., Why the huge price difference?
First time computer builder here and I want to use USB3, SATA3, and a Phenom x4, which (I think) means using either a 890fx or a 890gx (also I'm gonna use a 5770 GPU).
I realize that the 890gx has an on-board GPU which is the "real" difference, but I'm confused why it's ~$60 cheaper!
Here are the newegg links:
The 890fx tends to have more PCI slots. Is that a $60+ difference?
Some more questions: most of the gx boards mention "Crossfire/Hybrid Crossfire". Does this mean if I add a 5770 I get to leverage both the onboard GPU and the 5770 at the same time? Will this yield performance increases in games?
Finally, I wanted to go with a 5770 since it's within my price range, and in the future I can add a second 5770 to (cheaply) get better performance if I need it. Will I have a problem doing this on a 890gx which claims having 2 "PCI Express 2.0 x16" and "ATI CrossFireX/ Hybrid CrossFireX technology support"?
Thanks!
Posted Apr 28, 2010, 2:56 AM UTC · edited
Not an expert, but I was researching this exact question earlier tonight and it looks like no one else is answering.
From what I've been able to gather, yes. More accurately, the FX boards have more PCI-E lanes and higher bandwidth in their PCI-E slots. This means that you can Crossfire two cards at x16/x16 instead of the x8/x8 you might get on a GX motherboard.
But -- and this is another thing I've had trouble finding out for sure -- it sounds like the practical difference this will make for you with dual 5770s is minimal or none. I've heard that even top-end cards lose only something like three or four percent of their performance when run in an x8/x8 configuration compared to x16/x16.
My understanding is that Hybrid Crossfire only works with a very limited number of super low-end cards, and the results are pretty abysmal in any case. If you've got a dedicated graphics card, the onboard GPU will only be good as a backup in case it fails.
I'm looking at pretty much the same configuration as you (Phenom II X4, HD 5770 + possible second 5770 later) and I haven't come across any reason I would need an 890FX.
Yah, it's hard to learn this stuff because the 890fx just came out so web searches are filled with just speculation. Thanks for helping out!
This is the part that confuses me. The 5770 says its interface is "PCI Express 2.0 x16", so a single x16 slot, right?
A 890gx (say a Gigabyte ud3) says
To me that looks like it has two x16 slots and thus could fit two GPUs at x16/x16. Am I reading this wrong?
Edit: Yah, a google search and some quick skimming seems to confirm that an x8 does not bottleneck a 5770. Awesome! (at least on Intel boards. doubt this changes for am3).
The x16 slots share bandwidth, so (x16 or x8, x8) here means that they can run at x16 individually (only one in use) or at x8, x8 if both are used.
At least, I'm pretty sure they can both run at x16 individually. Sometimes only one slot can do x16, but the descriptions on those boards tend to say something like "If using only one video card, install in the blue slot."
Gotcha. Amazing that this whole x16 verse x8/x8+onboard GPU is a $60 difference, but it looks like performance/future-proofing wise I should be good to go with a 890gx. I'll save that money for the second 5770. Thanks!
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That's all pretty much correct.
You can find a 800-series Crossfire x8/x8 versus x16/x16 comparison right here. The difference is about 5% @ 1900x1200 using a $800+ pair of 5870s which are have exactly double the bandwidth, stream processors and texture units of a $320-$350 pair of 5770s. The difference is already small and would be negligible with the lower end cards.
Another thing...
890FX parts are brand new and as shown, there are only 3 examples available, from 2 premium brands - 2 flagship models and one that's a step down from.
Meanwhile, the 890GX has been available for over a month and show 8 examples from 6 manufacturers. If you compare the the FX and GX within the same brand and form factor you'll see a price difference of about $30, half of what OP is observing.
FX Being premium boards means that you simply won't see as many FX variations as GX as they cater to a different market, one where people are looking for the best and willing to pay for it.
Personally, I don't think the GX should even exist. It combines dual PCIE slots for use with high-end, dual discrete card setups and an IGP that anyone with a discrete card will never use.
Furthermore, unless you consider USB3/SATA6 a must have. The 700-series boards are cheaper across the board and offer the same performance. Of course, you'll want to be sure that a given 700-series board has an appropriate update for X6 support first.
Thanks for the input. I intend to use a SATA3 HD now (and possibly expand to SSDs in the future) and a USB3 external backup later, so I didn't want to go with the 700-series boards.