25 Mar
2010
25 Mar
'10
11:04 a.m.
Ralf Mardorf wrote:
David Olofson wrote:
My PCI Envey24 based card at least gives access to one of the Envy's
MPUs, unfortunately I wasn't able to use the Terratec EWX 24/96 MPU. I
tried different circuits using a BreadBoard. I won't buy a MIDI cable
from Terratec ;).
On Thursday 25 March 2010, at 13.32.43, David
Olofson
<david(a)olofson.net> wrote:
Mobo: M2A-VM HDMI
Graphics: ATI Radeon X1250-based graphics, *onboard*
Slot for another graphics is an PCI Express slot, no AGP etc.
The HDMI card is demounted from the PCI Express slot and HDMI is
disabled by the BIOS.
I'm not using a proprietary 3D driver and I wasn't able to test one,
because it doesn't work using Linux, even though there is a 3D driver
for this card and Linux, perhaps the problem is "...-based".
The USB MIDI interface is a 1 in and 1 out, very cheap swissonic.
I suspect the graphics and the USB device causing to much MIDI jitter.
I need to search for an old test, but have no time to do it right now,
but I do remember that Windows without HPET was better, than Linux
with HPET as sequencer timer source, while all other Linux sequencer
timer sources were much more out of time.
Btw. I don't think that Windows would solve this issue for me, the
jitter for my current system is bad with both OSs. I know people where
Linux is bad and Windows does solve this issue ... perhaps Windows
will cause other issues for them ;). On Thursday 25 March 2010, at 12.49.31, Ralf
Mardorf
<ralf.mardorf@alice-
dsl.net> wrote:
[...]
> Btw. the
> graphics has access to the main memory, unfortunately it's a shared
> RAM,
> OTOH I used HPET so unwanted interrupts because of a shared RAM
> shouldn't be the cause, if I do understand the workings of HR timers
> correctly.
>
[...interrupts, DMA etc...]
BTW, the most common problem with graphics and realtime systems seems
to be drivers abusing PCI port blocking as a performance hack. When
the command buffer on the video card is full, the PCI bus blocks the
CPU (completely - no IRQs, no nothing), instead of the driver going
to sleep and waiting for an IRQ or some other proper solution. Might
improve the 3D framerates slightly, but kills lowlatency audio...