Re: GGI, EGCS/PGCC, Kernel source

Wed, 25 Feb 1998 20:03:37 +0100 (CET)

On Wed, 25 Feb 1998, Alan Cox wrote:

> > IMHO, GGI still has no strong concepts to support accelerated operations
> > on PC GX cards. [...]

> Well it is in the release notes for the current one that acceleration
> basically isnt done yet. XAA over a kernel block queueing layer is
> doable (look at Solaris x86 for similar stuff)

command queueing in X is doable, and it works great. It's a high level
protocol, it gets thousands of calls per second. The accelerator of most
cards is a different beast though. It usually has a limited queue depth
(8, 16, 32), where a command can take up 1-5 queue entries. So certain
accelerated commands do not queue at all on the hardware level. There are
possibly millions of accelerated operations per second. Smallish
accelerated operations finish within 10-100 cycles, this is why almost no
GX card has IRQ-driven acceleration, they have an engine status/depth
register that can be polled. If you let users access the framebuffer as
well then 'delayed syncing' (a technique in XFree86 XAA that has almost
doubled acceleration performance ...) can not be done safely.

it's a _big_ task.

-- mingo

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