Other Uses for an AGP Slot? 160
SleepyHappyDoc asks: "AGP seems to be going the way of the dinosaur, but there's still a lot of slots on legacy motherboards out there. If you don't have need for the graphical advantages of AGP (say, on a headless server), what else could you use the AGP slot for? Could the advantages of AGP over PCI be leveraged in a use other than graphics cards?"
As I don't know of any AGP cards that aren't gfx.. (Score:4, Informative)
Well (Score:3, Informative)
Accelerated Graphics Port (Score:4, Informative)
Very limited usage, maybe (Score:5, Informative)
You could use it for something like a beefy sound board.. or, something...
No, not much other than graphics output really needs that kind of bandwidth differential.
Re:There was this project ... (Score:5, Informative)
Re:Use for old AGP cards? (Score:2, Informative)
Re:Very limited usage, maybe (Score:4, Informative)
Re:Leverage (Score:2, Informative)
http://www.thefreedictionary.com/dict.asp?Word=le
Re:Leverage (Score:3, Informative)
An Ask Slashdot post isn't exactly poetry, but using "leverage" as a verb is not only a de facto use of the word, it's also a recognized figure of speech.
AGP is a one-way architecture? Not. (Score:1, Informative)
That's a funny thing to say given that the highest rated post above yours is "VRAM Storage Device" [slashdot.org] which describes how to use the RAM on an AGP graphics card as block storage [linuxnews.pl].
One-way swap or filesystems just aren't that useful.
Besides, how do graphics cards read textures from system RAM if they can't signal anything back?
upstream vs. downstream (Score:3, Informative)
Someone mentioned doing video compression... because you could send the compressed file back. Well ok, except, A. video cards only have 256mb of ram... so your uncompressed video would only be like what 30 seconds? B. getting the data back to the hard drive would be like transfering files over a serial cable... like old PS/2 serial, not USB2 serial.
Now... a card with a SATA out would work. That's the kind of bandwidth that would help, although for most applications just an IDE out would do the trick.
But these cards don't exist. So no... nothing to be done with agp slots.
Re:upstream vs. downstream (Score:2, Informative)
AGP *IS* PCI, and then some... (Score:3, Informative)
AGP is a subset of PCI. The original AGP spec (1.0) defined a dedicated slot with a 32-bit, 66 MHz PCI connection directly to the Northbridge, plus the ability to directly access main memory more quickly than conventional DMA allowed. AGP 2x then increased speed by using a double data rate system, similar to DDR memory, transferring two data chunks per clock cycle.
AGP 4x then added a quad data rate connection, Fast Writes (the ability to write to main memory out of normal order,) and Direct Memory Execute (the ability for the AGP card to execute directly out of main memory, rather than having to load into on-board memory first.)
AGP 8x just oct-data rate'd it. It's still 32-bit, 66 MHz PCI, though.
But, either way, AGP *IS* a PCI connection. Fully compliant with PCI 2.1, with full bandwidth in each direction.
There are/were bridge chips that converted the AGP connection into one or more PCI slots, which would become fully-compliant PCI 32-bit, 66 MHz slots. These bridge chips were sometimes used on lower-end server motherboards with onboard PCI video, as a cheaper alternative to adding a separate 64-bit PCI controller. They could be found on products from Intel (L440GX,) and others.
BUT, since it is only 32-bit, you're limited to a 32-bit, 66 MHz PCI connection. PCI-X requires 64-bit for its faster bus speeds. That means that there are no bridge chips that will give you anything better than a 32-bit, 66 MHz PCI 2.1 connection. You can run multiple cards off this connection (As the Intel board listed above did,) but just as with 'regular' PCI, you are sharing the speed among all the cards.
But, any 66 MHz PCI card (or any correctly backwards-compatible PCI-X card,) would take advantage of the doubled speed over 33 MHz PCI, though.
See http://web.archive.org/web/20040205095311/http://
Re:AGP *IS* PCI, and then some... (Score:4, Informative)
It should be noted that the AGP bus in general has snooping turned off; the GART in the northbridge
handles all of the memory access therefore it can and should always tell when memory is being accessed
(therefore you can't rely on caching video memory like you would on a PCI card). Without snooping on
DMA transactions this speeds the bus up somewhat. It also lacks the interrupt routing lines. What this
basically means though, is that without a bridge chip, it ISN'T exactly the same as a PCI slot - if
you put more than one device on there, only the first will work, and even if you could, you'd
effectively trash memory every time you did PCI DMA.
As PCI ('frame mode') you're right, it's just a 66MHz 32-bit PCI slot. In fact we make two board
designs at the place I work, one of which puts an AGP slot onto a 66MHz 32-bit PCI bus (and it works
fine up to the point of having a 3.3V keyed slot, and the industry moving on to 1.5 and 0.8V devices)
and one which has a 66MHz 32-bit PCI slot which we ship an AGP riser for. Everything Just Works (tm).
AGP specs *also* has a USB connection routed to it but I dare say it's not been connected on most
motherboards since the dawn of AGP 2.0 (everyone seems to use I2C on the card and talk via some
kind of PCI configuration/register space logic instead).
There is plenty of stuff you can do with AGP but seriously who'd want to these days. You're picking
up old boards now, trying to do "cool" geeky things with them? What for? You're too cheap to move
to PCI Express?