Re: [9fans] nvidia scrolling performance

[Paul Lalonde <plalonde@telus.net>]

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8G/s? Nowhere near enough.  Enough for text, but try doing real
computation using that GPU...
PS3 is running 25G/s bi-directional.  Those bits move.

Paul

On 30-Apr-06, at 5:52 PM, erik quanstrom wrote:

> i only have a pci card, but someone with an agp card and a machine
> that
> allows bios-controlled agp bandwidth could eliminate some
> possibilities.
> if it's bus limited, then the total performance should be linear in
> agp
> bus speed, right?  of course we still wouldn't know which direction on
> the bus was limiting.
>
> perhaps it's time to add another machine to the second-hand
> hardware collection.
> ;-)
>
> pci-x (1.066G/s) has the same bandwidth as PCIe x4 (1G/s).
> PCIe SLI = 2 * 16x = 8G/s, which ought to be enough for just about
> anyone.
>
> - erik
>
> On Sun Apr 30 13:13:21 CDT 2006, steve@quintile.net wrote:
>>> Frame buffer memory is very very slow to read from,
>>> and not just on nvidia.  When I did some timings six years
>>> ago, I found that reading from frame buffer memory
>>> was slower than reading from disk.  I'm sure the situation
>>> hasn't gotten better.  It's not on the fast path for any
>>> other system, so the vendors just don't care.
>>
>> I may be talking rubbish but I understood this is a fundamental
>> problem with reading VGA memory over the PCI bus. VGA cards are
>> designed for fast writes and not fast reads.
>>
>> People have been very interested in using the GCPUs in graphics cards
>> to do video processing (to disk rather than for display) but the
>> limiting
>> factor seems to have been the speed at which data can be read back.
>> I do hear that some cards are appearing with dual PCIX which will
>> allow
>> symetric access speeds to the frame buffer.
>>
>> -Steve
>>

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