On 8/25/06, Jon Smirl <[EMAIL PROTECTED]> wrote:
> That's because they're using two separate GPU chips... at least in > Matrox's case. We're only a single PCI device. Software is > responsible for allocating framebuffers. There are then lots of > options available, such as independent displays and side-by-side > continuous displays that act as one across two monitors. NV/ATI are a single GPU and have two PCI devices. I believe Windows forces you to have one PCI device per head no matter how many GPUs you have.
I vaguely recall us running into this at Tech Source when developing the Windows driver for various Raptor cards. We worked around it somehow.
The GART hardware is almost always used since the CPU paging hardware has scrambled any images in system RAM. Resolving this scrambling is why normal DMA is seldom used.
I have two suggestions to solve this for us: (1) For the ring buffer (which doesn't need to he very large anyhow), if we want multiple pages, we'll just design the hardware to handle multiple base addresses that we stitch together. (2) For indirect buffers, software is responsible for dealing with page boundaries and submitting commands in multiple blocks (which translate into multiple commands queued up in the ring buffer).
> Many have said that 256MiB is enough for this. If not, we can alter > that before we ship OGC boards. Remember that those cards with 256MB also have full access to RAM from GART space. I'm not sure if anyone has measured the true memory consumption while these apps are running. People may think they fit into 256MB which they are actually spilling out into system memory.
These were discussions from when we were deep in discussions about OGA design. I think the people saying this were aware of OGA's limitations. _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
