AMD 790GX: RV610 For Enthusiasts?

AMD’s Peace Offering: SB750

790GX offers six additional lanes of PCI Express 2.0 connectivity that can be used by motherboard partners to integrate peripherals or enable expansion slots. AMD does not offer its own Gigabit Ethernet solution like Nvidia does, so there’s one PCIe link that’ll almost certainly be populated on 790GX-based boards.

The chip’s remaining four lanes of PCIe 2.0 constitute the connection between northbridge and southbridge. AMD brands the interface A-Link Xpress II and, if it were PCIe 2.0 on both ends, it’d deliver 4 GB/s of bi-directional throughput. Unfortunately, SB750 employs PCI Express 1.1, like its predecessor, capping bandwidth at 2 GB/s instead.

Making the Most

Once you make your way past the pedestrian chip-to-chip interconnect, you’ll find that there’s a lot more to like about SB750. On the superficial surface, USB 2.0 support remains pegged at 12 ports (with two 1.1 ports thrown in as well), HD Audio persists, a single parallel ATA channel accommodates two IDE devices, and six SATA 3 Gb/s port accommodate plenty of storage.

But whereas SB700 was limited to RAID 0, 1, and 10 arrays across its six ports, SB750 adds RAID 5 functionality to its list of accolades. That particular development is important because Nvidia and Intel already offer RAID 5, an increasingly popular mode for bolstering data security. AMD doesn’t say so in any of its supporting documentation, but we know from talking to company insiders that a particular effort went into improving the southbridge’s I/O performance, including its USB 2.0 and SATA components.

More important than RAID 5, expansive USB connectivity, or missing Gigabit Ethernet is a feature that AMD calls Advanced Clock Calibration, or ACC. There’s an aura of mystery shrouding what AAC actually does, which makes us nervous because vendors aren’t usually vague about the details of such potentially game-changing technologies unless there’s a good (bad) reason. What we do know about ACC is that it’s a direct, low-level link between the southbridge and CPU that AMD says “functions to unlock a number of tumblers on the processor previously not accessible.” Beyond that, with the proper cooling configuration, AMD claims simply enabling ACC is enough to boost overclocking headroom by between 100 and 400 MHz.

The feature comes most highly recommended for owners of Black Edition CPUs — the ones who’ve likely hit a wall with simple multiplier and voltage increases. But it will also work with any Phenom processor you drop into the 790GX platform. Given AMD’s reluctance to sing the specifics of ACC, we’ll have to let testing do the talking on this one.

The good news for true enthusiasts is that you won’t need to buy a 790GX with integrated graphics in order to reap the benefits of AMD’s SB750 southbridge. Fairly quickly we’ll start seeing 790FX-based motherboards retrofitted with the new component, bringing improved storage and overclocking to what we’d consider the true power user platform in AMD’s portfolio. The 790GX will be rightly confined to the folks able to use its integrated graphics core in a Hybrid CrossFire arrangement. In more rare cases, it may be tapped for its CrossFireX capabilities, though we’d just as soon go for one of the less expensive 790FX platforms sporting SB750. Originally we had hoped that the 790X platform would also receive some SB750 love. It’d seem to make sense as an alternative for budget-oriented gamers looking for an affordable CrossFireX setup without the need for integrated graphics. AMD doesn’t anticipate any of its partners taking that route, though.

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71 comments
    Your comment
  • kitsilencer
    Great review, and it's good to see that AMD is at last able to target more enthusiast markets competitively.
    6
  • cangelini
    kitsilencerGreat review, and it's good to see that AMD is at last able to target more enthusiast markets competitively.


    Thanks for the feedback Kit.
    0
  • eklipz330
    ^^^iseriously thought that was sarcasm, until i saw the authors name
    1
  • waffle911
    So... why does a page 15 and 16 of this article exist if there is no page 15 or 16 to the article?
    Take a closer look. What happened?
    0
  • YYD
    PCMark seems Intel biased, please read this:
    http://arstechnica.com/reviews/hardware/atom-nano-review.ars/6

    Please change this benchmark suite or check if PcMark Vantage is unbiased.
    2
  • cangelini
    waffle911So... why does a page 15 and 16 of this article exist if there is no page 15 or 16 to the article?Take a closer look. What happened?


    That was strange. Should be fixed now.
    0
  • cangelini
    YYDPCMark seems Intel biased, please read this:http://arstechnica.com/reviews/har [...] view.ars/6Please change this benchmark suite or check if PcMark Vantage is unbiased.


    Fortunately, with no Intel platforms tested, this should be a non-issue for the current situation ;-) In the future, you'll be seeing SYSmark, though.
    0
  • Anonymous
    Seems past page 8 or something the links are corrupt.. can't fully read this article and getting error 404 - page not found.
    1
  • Anonymous
    .. and now the article seems to be removed even from the main page!?!?!
    1
  • cangelini
    lacrits.. and now the article seems to be removed even from the main page!?!?!


    Alright, mystery solved. It's back up, sans the blank page. Thanks for pointing that out lacrits!
    0
  • nickchalk
    Hi, i wanted to ask something aout the article.
    why you use 3470 and 8500 for the tests?
    hybrid crossfire and nvidia boost don't work with faster cards?
    is the performance gain not big with 3870 or 9600gt?
    thanks
    2
  • cangelini
    Hybrid CrossFireX uses alternate frame rendering, as does GeForce Boost, I believe. As a result, both technologies are best complemented by discrete boards evenly matched to the integrated core. In the case of the GeForce 8300, that'd be an 8500 GT. For the 790GX, AMD recommends the 3470. To spend any more money on discrete graphics for either platform would be a waste of money even if you could use faster cards.
    2
  • nickchalk
    thanks for responding so fast.
    so what if i use a 3650 with this board? or why will i buy a quad core and dont spend some more for a 3850?
    1
  • cangelini
    Unfortunately, performance won't scale with the 3650. With that said, you'll still see reasonable gaming performance in Hybrid CrossFireX. The beauty of this board is that you CAN drop in a 3850, 3870, 4850, etc. and then add a second one later for CrossFireX.
    0
  • zenmaster
    cangeliniUnfortunately, performance won't scale with the 3650. With that said, you'll still see reasonable gaming performance in Hybrid CrossFireX. The beauty of this board is that you CAN drop in a 3850, 3870, 4850, etc. and then add a second one later for CrossFireX.


    Nice Review, However I would like to see how well SLI scales on this board using a 4850 and 4870 vs another AMD Board with full Duel 16x PCIE 2.0 Slots.

    I've seen some other reviews where Dual 8x PCIE 2.0 Slots start having scaling issues on the 4850 at are not seen on the 3800 Series.
    0
  • computerfarmer
    Thank you for this excellent article.
    Does the 128mb side-port limit the on board video to that amount of memory? Does this affect Vista Areo?
    1
  • jimmysmitty
    Good article. Phenom can finally OC. I wounder if the mobo makers are going to make them with higher quality voltage regulators so it can support the 9850BE and higher across the selection.
    1
  • cshorte
    good review,

    i have a question why do you recommend ddr1066 over 800? i thought there wasn't a huge difference.

    also im a bit confused about this 16x, vs. 8x 8x...
    if i use a single card (for now) which motherboard (790g, 790gx) will produce more graphixs capabilities?
    1
  • ltcommander_data
    It would have been interesting to see a comparison between the GMA X4500 and the 790GX.

    http://www.hkepc.com/?id=1510&page=5&fs=idn#view

    The GMA X4500 seems to be much faster than the GMA X3500 and within 10-30% of the 780G in actual games. I guess the 790GX was a timely addition and with it being 20% faster than the 780G, that should open up the lead over the GMA X4500 to 30-50%.
    1
  • kenyee
    and which of these upcoming 790GX motherboards are microATX?
    The only one I know of is the DFI one...
    1