RE: Legacy Terminology RE: DMA across PCI

[Lame Brooks-G14738 <brooks.lame@motorola.com>]

I think you just said it yourself, Ted: a "DMA engine."   That's the old ISA
terminology refering to a state machine that manages data transfers.  I'm
only pointing out that the term DMA in reference to PCI does not indicate
any specific implementation nor performance capabilities.  And, because the
term is so non-specific, it has little meaning to engineers in PCI.  With
marketing liturature on the other hand, they throw in all the buzz words
they  can.   :P     -- BrooksL

> -----Original Message-----
> From: Ted Firlit [mailto:firlit@utmc.aeroflex.com]
> Sent: Thursday, 14 December, 2000 12:46
> To: Lame Brooks-G14738
> Cc: 'Daniel DeConinck'; PCISIG List (E-mail)
> Subject: Re: Legacy Terminology RE: DMA across PCI
> 
> 
> I'm using a Galileo PCI controller chip (GT64120A) which specifically
> implements a 4-channel DMA engine for the host CPU to set up DMA
> transfers.  I didn't think this was so unusual for a PCI 
> controller chip
> to do.  If and when we change out this chip, I'll expect the 
> replacement
> to implement DMA as well,  unless you know something about DMA and PCI
> which I don't.
> 
> TedF
> 
> Lame Brooks-G14738 wrote:
> > 
> > Yeah, years ago when I was a newbie to PCI, I got smacked 
> on the head for
> > using DMA in reference to PCI.  DMA is an ISA bus related 
> acronym that
> > stands for Direct Memory Access.  PCI is by definition all 
> about direct
> > memory access - that's one of the features that made it 
> superior to ISA!
> > Therefore, the old term DMA itself has little meaning in 
> reference to PCI.
> > I think most of the people who try to use it now days are 
> meaning a concept
> > analgous to the legacy ISA DMA Transfer Engine which is 
> simply a state
> > machine that can manage a block data transfer given the 
> start and end
> > addresses.  I'd stay away from legacy terminology when talking about
> > specific bus behaviour like burst transfers.   -- BrooksL
> > 
> > -----Original Message-----
> > From: Daniel DeConinck [mailto:daniel.deconinck@sympatico.ca]
> > Sent: Saturday, 14 October, 2000 09:48
> > To: pci-sig@znyx.com
> > Subject: DMA across PCI
> > 
> > Hello,
> > 
> > I looked in the index of the PCI spec 2.1 and the index of 
> "PCI System
> > Architecture", by Mindshare, Inc. Niether had a reference to DMA.
> > 
> > I am guessing that there is no such thing as DMA in the PCI 
> world. Is that
> > the case ?
> > 
> > I further guess that the closest thing to DMA is a Master 
> read or a Master
> > write cylce.
> > 
> > Please enlighten me.
> > 
> > Sincerely
> > Daniel DeConinck
> > High Res Technologies, Inc.
> > 
> > 
> 
> -- 
> Ted Firlit		      		(719) 594-8138
> Senior Design Engineer
> UTMC Microelectronics Systems
> 4350 Centennial Blvd., MS 1004
> Colorado Springs, CO 80907
>