Graphics card for UP1500, AGP Compatibility and Signalling Voltages

[Alex Deucher]

On Thu, Nov 27, 2008 at 12:22 AM, Matt Turner <mattst88 at gmail.com> wrote:
> Hi,
>
> I'm attempting to determine what graphics cards are compatible with
> the Samsung UP1500 motherboard.
>
> It uses the AMD-761 chipset, which according to both the UP1500 user
> manual and this Wikipedia article
> (http://en.wikipedia.org/wiki/Comparison_of_AMD_chipsets) supports AGP
> 4x.
>
> AGP 4x is defined as using 1.5v signalling voltages, whereas older
> 1x/2x AGP used 3.3v. To prevent you from frying your card, AGP slots
> are keyed. See http://en.wikipedia.org/wiki/AGP#Compatibility
>
> Now, if you look at the picture of a UP1500 motherboard
> (http://alphalinux.org/wiki/index.php/Image:UP1500.jpg), it clearly
> has the 3.3v key. This limits the available cards to Radeons through
> the R300 series. I'd really like an AtomBIOS-enabled R500 to be able
> to go straight from the blue backgrounded SRM console to a nice kernel
> modesetting environment, but without the correct AGP keys, this can't
> happen.
>

Your best bet is probably a PCI r3xx or r5xx card.  AGP is broken by
design and it's best to avoid it.  Also, drm kernel modesetting
support both legacy and atombios based cards, so either will work.

> What's going on? AGP 4x is supported by the board, but not the
> appropriate signalling voltages?
>

Even though the chipset supports 4x in theory, the motherboard may
only support 3.3 volt cards.  Perhaps there were issues with providing
1.5 volts to the slot.  It could also be that it's really just a PCI
slot with an AGP connector.  There are some PPC boards like that.

Alex