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  • KristopherKubicki - Saturday, June 12, 2004 - link

    The AGP port has always been a hack on the PCI bus anyway - electrically it isnt that much different so this *does* make sense.

  • KalTorak - Monday, June 07, 2004 - link

    Derek - an x16 interface has sixteen diff pairs going each way, for a total of 64 signal lines. 4GB/s each way, simultaneously.

    This should also resolve your dilemma about the x1 interface - one pair in each direction, four total wires.

    As for getting a PCI-E spec, see if Anand can just join PCI SIG. :)
  • Minot - Sunday, June 06, 2004 - link

    Did Asrock do the same thing getting an AGP port on an Intel 865GV chipset motherboard? Their P4I65GV has what they call A.G.I. (Asrock Graphics Interface). It would make sense to me that this is also an implementation using the PCI bus interface. Or did they do something entirely different to get true AGP on that chipset? Reply
  • MIDIman - Saturday, June 05, 2004 - link

    Hey - its a digital camera right? You should've just showed the Gigabyte people the picture that you took earlier! "Oh, that's clearly been doctored with Photoshop..." Reply
  • Gandalf90125 - Friday, June 04, 2004 - link

    " can actually run an AGP card in PCI mode, giving up all of the benefits of AGP obviously."

    Can anybody say "3dfx"?
  • Bozo Galora - Friday, June 04, 2004 - link

    Much better more informative series of articles lately. Thumbs up.

    As far as the AGP pipeline, I think that it's the reason for most of the probs today with freezing, reboots and dumping to desktop. In the ATI smartgart tab you might find the AGP set to "0" (not 4X or 8X) by the self testing proceedure. What this means is that the AGP bus is shut off to the supposedly contiguous (gart) system memory address tables set in RAM. With a 128MB card probably, and a 256MB card definitely, it never has to offload work to the memory anyway, it does all work internally. People misrepresent this as no AGP, but if the card is set to 8X in BIOS, the cards mode is AGP VOLTAGE and IS much faster than AGP MODE (no busing involved), until it has to offload something, and cant (slowdown). We DO need a PCI high end videocard, because AGP 4X/8X is a failure. Remember the loop??? I want a NO AGP bus/gart table 1GB vram superfast memory PCI vidcard. Who cares about the bus.

    And heres your 89 page AGP 8X nightmare.

    I just bought a 9800pro and its a non functioning piece of crap. So now I have to go thru the endless driver in/out shuffle. I am really getting tired of this. The fact yours may work perfectly is irrelevant - for the average Joe, its a hopeless situation.

    Why the hell cant I just put in a card, load the drivers and have it work 100% - is that asking too much?? If a game or app doesnt work with a state of the art card they should not be allowed to sell it.

    What a business.

  • DerekWilson - Friday, June 04, 2004 - link

    Meh ... PCI Express nominclature (or maybe its explaination) could use some work ... maybe we'll do some in depth analysis for our first x16 vid card reviews ...

    The problem this: PCI Express for Graphics, which is x16, is defined (as I understand it) as 8 dedicated up and 8 dedicated down lines. You could call it full duplex with 8GB/s, or 4GB/s in each direction or whatever ... But does PCI Express x1 work the same way? It wouldn't be really possible since you'd have only one direction of communication (which wouldn't work for anything). So why don't they call the base spec x2 (since its got 250MB/s in each direction)? or why isn't the graphics spec called x8 (if each pair of up and down lines is called a connection as in x1)?

    I've gotta check with Anand to see if he's been able to purchase or aquire the PCI Express specification yet ...
  • Filibuster - Friday, June 04, 2004 - link

    >maximum of 500MB/s (8GB/s / 16)

    For full duplex, yes. Only 250MB/s in one direction, and almost all video traffic goes one way.
    Also, 133MB/s for standard PCI does not account for it's overhead either, so comparing the two theoretical speeds is probably best overall.
  • dvinnen - Friday, June 04, 2004 - link

    Seems like it would be easier to drop a nVidia-like bridge chip into the mother board it's self. I wouldn't think they need much tracing. Reply
  • DerekWilson - Friday, June 04, 2004 - link

    oh .. and if these guys wanted to do build something with less of a performance impact, they could run the AGP card in 2x mode, drop in a buffer to build up 64bit packets of data (rather than the 32bits on the interface) and hook it up to a 64bit 66MHz PCI bus.

    That'd basically quadruple the bandwidth they're looking at right now with a glorified PCI slot.

    Of course, maybe my idea is harder to impliment than I'm thinking ... but engineers are engineers for a reason right? Crack the whip!
  • DerekWilson - Friday, June 04, 2004 - link

    so 32bit 33MHz has a max bandwidth of 133MB/s obviously (4 bytes * 33.3 MHz) ...

    maybe if we could ever get a copy of the actual PCI Express specifications we could tell you just how much data you could transfere (its not as easy as width times speed since bus utilization is much lower due to the fact that control signals must also be sent serially).

    If we are to believe what we've been hearing about x16 PCI Express with graphics cards, then we would talking about a maximum of 500MB/s (8GB/s / 16) ... Though the effective bandwidth could be much lower than that (though probably not lower than 256MB/s) depending on what kind of control and signallling goes on. So x1 PCIe is, at maximum, less than a quarter of the speed of AGP 8x. Which means it will also be much less (utilization issues) than the speed of a 64bit 66MHz PCI slot (533MB/s).

    the nice little x4 PCIe slots will do well for high bandwidth devices that need something like a 64bit 66MHz PCI or a PCI-X slot right now (I'd like four gigabit ethernet ports in one slot please).
  • Filibuster - Friday, June 04, 2004 - link

    >Why don't they put the AGP on a PCI-Express 1x instead of the old 32-bit 33 MHz PCI?

    Because PCIexpress is serial and PCI/AGP are parallel, so it would be much more difficult to adapt. Basically the HSI chip Nvidia is using would have to be on the motherboard, along with any trace design that it requires.

    1X PCIExpress isn't much faster than standard PCI either, at least when you compare it to 2G/s AGP.
  • kherman - Friday, June 04, 2004 - link

    I'll laugh if Intel AGP cards don't work because they didn't follow the AGP standard. Didn't they drop the ball on that once before with AGP slots. Something about supporting both 3.3V and 5V interfaces to AGP slots? Reply
  • AtaStrumf - Friday, June 04, 2004 - link

    Why don't they put the AGP on a PCI-Express 1x instead of the old 32-bit 33 MHz PCI? Reply
  • skiboysteve - Friday, June 04, 2004 - link

    crazy bastards Reply

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