Ralf Mardorf wrote:
> David Olofson wrote:
>> On Thursday 25 March 2010, at 13.32.43, David Olofson
>> <david@email-addr-hidden> wrote:
>>
>>> On Thursday 25 March 2010, at 12.49.31, Ralf Mardorf
>>> <ralf.mardorf@email-addr-hidden-
>>> 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...
>>
>
> 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 ;).
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 ;).
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Received on Thu Mar 25 16:15:03 2010
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