Do pci TV-Tuner cards need DMA?

[keropi]

Wwwweeeellll....
I will install a Fusion878a tuner on my G-Rex, but unfortunately it's the 1st version, so it only has 1 proper DMA pci slot, currently hosting a ess solo-1 soundcard. Will a tuner card work on a non-dma pci slot? or will it have problems?
I remember that I checked in windows a phillips 7134 based card and it did not report to use a dma channel, but this is amiga and a different chip...
So?

[Charlie]

Sorry can't guarantee, but TV cards shouldn't need DMA & I've not come across one that does. ( Fancy hardware PVR-type cards may be a differnet story. )

As a double-check see if the PCI card you're after is sold as a USB version.

[patrik]

I have to disagree. All modern tv-cards as far as I know use dma to transfer the data directly to the graphics-card as it would be insane to use the cpu to shuffle that amount of data.

Also in a classic Amiga, it is almost guaranteed that the bus between the cpu and the tv-card would be too slow to pull that of.

Just consider a very low resolution 320x240 ARGB stream of data with 50 images per second - that is 320*240*4*50 = 15360000B/Sec ~= 15MB/Sec. And that would just account for reading the data from the TV-card - then you have to write it back to the graphics-card which is on the same bus in this case. Thus the needed bandwidth is the double of that - approximately 30MB/Sec.

The only classic Amiga that could have a chance of pulling that of as far as I know would be an A4000 with a CSPPC/MK3, a Grex with a Voodoo and preferrably a 060 clocked from the same 66MHz oscillator as the 604e and the Grex bus to synchronize the buses.

Btw, the dma channel stuff is old isa legacy stuff. If you want to check if a pci-card is able to do dma-transfers, check if it has the bus-master flag set. Though, this does only tell that it _can_ do dma-transfers, it doesnt tell if it will only do transfers with dma, but if a tv-card has the bus-master flag set, you can be sure that it is designed to use dma-transfers for the video-stream. Other cases are different - more versatile devices, like graphic cards can in most cases fetch data from the normal ram of the computer by using dma transfers and thus has the bus-master flag set, but that is a seldom used function when they are in Amigas.

[Mad-Matt]

Well thankfully very little cpu is needed on miggy. At least on mediator that has no concept of dma, its just uses raw bus-mastering to render the decoded image directly to the gfx cards hardware overlay, so cpu doesnt need to worry. Capturing is another matter alltogether, but watching isnt an issue.

[Charlie]

@patrik:
I stand corrected...

My belief was that TV Cards may have DMA & this is good, but if the bus doesn't support it this is not required for function with a typical amiga setup. ( Though without it trying to stream a tv signal to HDD will run into cpu overhead problems. )
My point about USB was a practicable quick check. If the particular chipset is known to function through USB ( no good for an Amiga ) you have a good chance it won't be too demanding for the above PCI solution.

Am I completely wrong?

[patrik]

@Charlie:

Nowadays the industry doesnt skimp on the dma capability on of cards, so whenever it is sensible, it is used, which is just about always .

I dont know about the usb-check. I can tell you one thing though and that is that you will most likely atleast not find the exact same chip inside a usb-solution, as that would make the chip have ~100 extra pins for the pci-bus, which would be unused and that would be very uneconomical as the chip-package would be much much larger than required.

And yeah, dma over the pci-bus to the graphics-card will definately be required for a tv-card to function properly in a classic Amiga as the system cant really manage shoving around such amounts of data in another way.