Multiple Dma System?

[osknockout 0]

Do commerical systems with multiple DMAs exist in the PC price range? I heard about Super DMA testing last year at satelliteguys.us and I was wondering if any company actually sells these systems.

[whyme 0]

I'm almost positive that multiple DMA Computers aren't in the public market, and only reside on university servers and labs.



edit: ***
For those who had no idea what this topic is about(and I'll say that's almost everyone, since no one replied to this thread... ), it is talking about Direct Memory Access, a method of transferring data from one memory area to another without having to go through the central processing unit. This makes your computer run faster and put less load on your CPU.

Assuming that you haven't DMA'ed your system, here's the full tutorial on how to do it.

http://www.real-knowledge.com/dma.htm

Edited April 19, 2005 by whyme (see edit history)

[alperuzi 0]

Not sure what you mean by multiple or super DMA, all devices which do block transfers today use DMA, they have to... otherwise there would be way too much congestion of the CPU.What you guys usually hear advertised is harddisks using DMA, but in truth devices like the graphics adapters, even ethernet adapters use DMA...With Serial ATA all the UDMA madness have stopped...

[alperuzi 0]

oh, btw, PCs always have had multiple DMA channels... I think there are like 10-12 of them. In the days before PlugNPlay you used to assign every device a DMA channel manually

[osknockout 0]

Alperuzi, I mean multiple DMA devices when I talk about multiple DMAs. DMAs have several DMA channels, so more DMA's would let the general system go even faster if implemented correctly -that's why I asked . Thanks whyme, although I'm wondering... how would one build a multiple DMA system? I mean I don't think there are DMA slots in existence.

[alperuzi 0]

Each channel is assigned to a device.Pretty much all devices use DMA. DMA's don't have multiple channels... because a DMA (Direct Memory Access) is a process, not a physical thing. It involves the CPU setting up a transaction line between a initiator and a target and then forget about the transaction itself rather than passing every word one by one. A system has like 12 DMA channels, and each goes to a device (this is transparent nowadays, since USB and PCI-Express work in much more sophisticated ways).DMA is used in block transfers. What is a block transfer? An example is like a graphics adapter which requests whole sections of memory at once, or harddisks which read and write in blocks rather than one byte at a time (gee, that would take forever).So what is done? The device or the CPU tells how many blocks it needs, tells the address of the blocks and then then as a response after a number of clock cyles starts receiving the data staight from the memory or writes straight to the memory.Things like mice, keyboard don't use DMA, since they need to generally transfer a few bytes of information every second.UDMA2-3-4-5 is just increase in bandwidths between harddisk and physical memory. This enables faster transaction between the two. On the other hand, graphics cards and such can access physical memory at much faster speeds (since they are not disks). These are usually synchronized to some clock unlike IDE lines for harddisks (PCI clock is 33Mhz, 66 for AGP, 133 for AGP2x, 266 for AGP 4x...)Okay, that was kinda long... sry, just wrote the final for this course, and it was waay too long too... couldn't finish it... I'll shut up now

[osknockout 0]

Ah, I see where we're differentiating in the definition of DMA. I mean a DMA chip such as the 8237 Direct Memory Access Controller (a.k.a the DMA) I don't mean the process of Direct Memory Access Transfer.Yeah, I was about to ask you why the heck you're telling me this textbook stuff. Yeah and that block transfer does up to 64 K block transfers. The controller I'm talking about had 4 channels, seems the recent one has twelve. Take that new skool! Sorry, was up till 3 last night. By the way DMA has nothing directly to do with disks, they're just used a lot for disk I/O.