While brushing up on the V2Pro, I saw in the data sheet where they actually define what a Logic Cell is, "Logic Cell = (1) 4-input LUT + (1)FF + Carry Logic". When I read this I thought maybe Xilinx has finally started printing facts in their data sheets about logic cell counts rather than marketing numbers. But no, somehow Xilinx still can't count and they are saying that 3,008 slices are equal to 6,768 logic cells. If Xilinx is going to define a logic cell, it makes sense to me that they should actually start counting them! -- Rick "rickman" Collins rick.collins@XYarius.com Ignore the reply address. To email me use the above address with the XY removed. Arius - A Signal Processing Solutions Company Specializing in DSP and FPGA design URL http://www.arius.com 4 King Ave 301-682-7772 Voice Frederick, MD 21701-3110 301-682-7666 FAX
Now I am really confused!
Started by ●August 9, 2004
Reply by ●August 9, 20042004-08-09
This debate is getting long in the tooth. Just take the number of slices and divide by two. In the meantime, Altera has jumped on this bandwagon and they multiply their ALE numbers by 1.25. As long a there is Marketing, there will be "creativity" with numbers. Just grin and bear it! Peter Alfke> From: rickman <spamgoeshere4@yahoo.com> > Reply-To: john@bluepal.net > Newsgroups: comp.arch.fpga > Date: Mon, 09 Aug 2004 13:46:36 -0400 > Subject: Now I am really confused! > > While brushing up on the V2Pro, I saw in the data sheet where they > actually define what a Logic Cell is, "Logic Cell = (1) 4-input LUT + > (1)FF + Carry Logic". When I read this I thought maybe Xilinx has > finally started printing facts in their data sheets about logic cell > counts rather than marketing numbers. But no, somehow Xilinx still > can't count and they are saying that 3,008 slices are equal to 6,768 > logic cells. > > If Xilinx is going to define a logic cell, it makes sense to me that > they should actually start counting them! > > -- > > Rick "rickman" Collins > > rick.collins@XYarius.com > Ignore the reply address. To email me use the above address with the XY > removed. > > Arius - A Signal Processing Solutions Company > Specializing in DSP and FPGA design URL http://www.arius.com > 4 King Ave 301-682-7772 Voice > Frederick, MD 21701-3110 301-682-7666 FAX
Reply by ●August 9, 20042004-08-09
Now I am more confused. If I divide the number of slices by two, I get a number that is more than 4 times less than what is given in the data sheet. I don't understand how Altera data sheets relate to your data sheets. If marketing is going to write your data sheets, can you at least get them to give an honest definition of the logic cell??? "Logic Cell = ((1) 4-input LUT + (1)FF + Carry Logic) * 1.125" I don't care how you market, but right now your data sheets are not consistent and will confuse anyone who does not read this newsgroup. Peter Alfke wrote:> > This debate is getting long in the tooth. > Just take the number of slices and divide by two. > In the meantime, Altera has jumped on this bandwagon and they multiply their > ALE numbers by 1.25. > As long a there is Marketing, there will be "creativity" with numbers. > Just grin and bear it! > Peter Alfke > > > From: rickman <spamgoeshere4@yahoo.com> > > Reply-To: john@bluepal.net > > Newsgroups: comp.arch.fpga > > Date: Mon, 09 Aug 2004 13:46:36 -0400 > > Subject: Now I am really confused! > > > > While brushing up on the V2Pro, I saw in the data sheet where they > > actually define what a Logic Cell is, "Logic Cell = (1) 4-input LUT + > > (1)FF + Carry Logic". When I read this I thought maybe Xilinx has > > finally started printing facts in their data sheets about logic cell > > counts rather than marketing numbers. But no, somehow Xilinx still > > can't count and they are saying that 3,008 slices are equal to 6,768 > > logic cells. > > > > If Xilinx is going to define a logic cell, it makes sense to me that > > they should actually start counting them! > > > > -- > > > > Rick "rickman" Collins > > > > rick.collins@XYarius.com > > Ignore the reply address. To email me use the above address with the XY > > removed. > > > > Arius - A Signal Processing Solutions Company > > Specializing in DSP and FPGA design URL http://www.arius.com > > 4 King Ave 301-682-7772 Voice > > Frederick, MD 21701-3110 301-682-7666 FAX-- Rick "rickman" Collins rick.collins@XYarius.com Ignore the reply address. To email me use the above address with the XY removed. Arius - A Signal Processing Solutions Company Specializing in DSP and FPGA design URL http://www.arius.com 4 King Ave 301-682-7772 Voice Frederick, MD 21701-3110 301-682-7666 FAX
Reply by ●August 9, 20042004-08-09
Peter Alfke wrote:> This debate is getting long in the tooth. > Just take the number of slices and divide by two. > In the meantime, Altera has jumped on this bandwagon and they > multiply their ALE numbers by 1.25. > As long a there is Marketing, there will be "creativity" with numbers. > Just grin and bear it! > Peter AlfkeOur stuff still has a way to go before it catches up with the real smoke and mirror artists. Did the Citroen 2CV ever have a two horsepower engine, even when first introduced - whenever that was? Actually I don't understand that one... it's as if X advertised "Virtex-4: more than one LUT"
Reply by ●August 9, 20042004-08-09
ok, I should have said multiply by two. I just think this argumenting about an extra 12.5%, silly as it may be, is not worth our combined efforts. Everybody knows where the factor comes from, most of us disagree with the reasoning. Grin and bear it. Do you want to argue about the meaning of "100%" in wine merchandizing? Do you want to fight the funny factor two in the "%proof" calculation? Or have you measured a "2 by 4 inch" piece of lumber? There is lots of fiddling with numbers going on... Peter Alfke> From: rickman <spamgoeshere4@yahoo.com> > Reply-To: john@bluepal.net > Newsgroups: comp.arch.fpga > Date: Mon, 09 Aug 2004 15:28:54 -0400 > Subject: Re: Now I am really confused! > > Now I am more confused. If I divide the number of slices by two, I get > a number that is more than 4 times less than what is given in the data > sheet. > > I don't understand how Altera data sheets relate to your data sheets. > If marketing is going to write your data sheets, can you at least get > them to give an honest definition of the logic cell??? > > "Logic Cell = ((1) 4-input LUT + (1)FF + Carry Logic) * 1.125" > > I don't care how you market, but right now your data sheets are not > consistent and will confuse anyone who does not read this newsgroup. > > > Peter Alfke wrote: >> >> This debate is getting long in the tooth. >> Just take the number of slices and divide by two. >> In the meantime, Altera has jumped on this bandwagon and they multiply their >> ALE numbers by 1.25. >> As long a there is Marketing, there will be "creativity" with numbers. >> Just grin and bear it! >> Peter Alfke >> >>> From: rickman <spamgoeshere4@yahoo.com> >>> Reply-To: john@bluepal.net >>> Newsgroups: comp.arch.fpga >>> Date: Mon, 09 Aug 2004 13:46:36 -0400 >>> Subject: Now I am really confused! >>> >>> While brushing up on the V2Pro, I saw in the data sheet where they >>> actually define what a Logic Cell is, "Logic Cell = (1) 4-input LUT + >>> (1)FF + Carry Logic". When I read this I thought maybe Xilinx has >>> finally started printing facts in their data sheets about logic cell >>> counts rather than marketing numbers. But no, somehow Xilinx still >>> can't count and they are saying that 3,008 slices are equal to 6,768 >>> logic cells. >>> >>> If Xilinx is going to define a logic cell, it makes sense to me that >>> they should actually start counting them! >>> >>> -- >>> >>> Rick "rickman" Collins >>> >>> rick.collins@XYarius.com >>> Ignore the reply address. To email me use the above address with the XY >>> removed. >>> >>> Arius - A Signal Processing Solutions Company >>> Specializing in DSP and FPGA design URL http://www.arius.com >>> 4 King Ave 301-682-7772 Voice >>> Frederick, MD 21701-3110 301-682-7666 FAX > > -- > > Rick "rickman" Collins > > rick.collins@XYarius.com > Ignore the reply address. To email me use the above address with the XY > removed. > > Arius - A Signal Processing Solutions Company > Specializing in DSP and FPGA design URL http://www.arius.com > 4 King Ave 301-682-7772 Voice > Frederick, MD 21701-3110 301-682-7666 FAX
Reply by ●August 9, 20042004-08-09
On Mon, 09 Aug 2004 15:28:54 -0400, rickman wrote:> Now I am more confused. If I divide the number of slices by two, I get > a number that is more than 4 times less than what is given in the data > sheet. > > I don't understand how Altera data sheets relate to your data sheets. > If marketing is going to write your data sheets, can you at least get > them to give an honest definition of the logic cell??? > > "Logic Cell = ((1) 4-input LUT + (1)FF + Carry Logic) * 1.125" > > I don't care how you market, but right now your data sheets are not > consistent and will confuse anyone who does not read this newsgroup. > > > Peter Alfke wrote: >> >> This debate is getting long in the tooth. >> Just take the number of slices and divide by two. >> In the meantime, Altera has jumped on this bandwagon and they multiply their >> ALE numbers by 1.25. >> As long a there is Marketing, there will be "creativity" with numbers. >> Just grin and bear it! >> Peter Alfke >> >> > From: rickman <spamgoeshere4@yahoo.com> >> > Reply-To: john@bluepal.net >> > Newsgroups: comp.arch.fpga >> > Date: Mon, 09 Aug 2004 13:46:36 -0400 >> > Subject: Now I am really confused! >> > >> > While brushing up on the V2Pro, I saw in the data sheet where they >> > actually define what a Logic Cell is, "Logic Cell = (1) 4-input LUT + >> > (1)FF + Carry Logic". When I read this I thought maybe Xilinx has >> > finally started printing facts in their data sheets about logic cell >> > counts rather than marketing numbers. But no, somehow Xilinx still >> > can't count and they are saying that 3,008 slices are equal to 6,768 >> > logic cells. >> > >> > If Xilinx is going to define a logic cell, it makes sense to me that >> > they should actually start counting them! >> > >> > -- >> > >> > Rick "rickman" Collins >> > >> > rick.collins@XYarius.com >> > Ignore the reply address. To email me use the above address with the XY >> > removed. >> > >> > Arius - A Signal Processing Solutions Company >> > Specializing in DSP and FPGA design URL http://www.arius.com >> > 4 King Ave 301-682-7772 Voice >> > Frederick, MD 21701-3110 301-682-7666 FAXPeter should have said multiply by two instead of divide by two. There are two LUTs in a slice, 4 slices in a CLB. So take the number of slices and multiply by 2 to get LUTs. It looks like Xilinx is also counting the IOBs in their logic cell count.
Reply by ●August 9, 20042004-08-09
Peter Alfke wrote:> > ok, I should have said multiply by two. > I just think this argumenting about an extra 12.5%, silly as it may be, is > not worth our combined efforts. > Everybody knows where the factor comes from, most of us disagree with the > reasoning. Grin and bear it. > Do you want to argue about the meaning of "100%" in wine merchandizing? Do > you want to fight the funny factor two in the "%proof" calculation? Or have > you measured a "2 by 4 inch" piece of lumber? There is lots of fiddling > with numbers going on...I agree Peter, this is not really worth much effort. I don't understand why you bring in unrelated issues such as the proof of spirits or the size of lumber. A 2x4 is sized according to a spec, no one says it is 2" x 4". The proof of spirits is not percentage, so I don't see why you are comparing the two, again, this is clearly stated. But the V2Pro data sheets defines a logic cell one way and are counted another way that is not discussed unless someone reads your posts here on the newsgroup. I understand who is doing it and why. At one point I thought it was just a matter of marketing getting into the data sheets. But if they contradict their own definition of what a logic cell is, then the data sheet contains falsehoods. If you don't want to discuss it, then feel free not to. I am not trying to sound rude or insulting. I belive I have only stated facts. So please don't feel that I have a grudge, I am just trying to get the facts straight. -- Rick "rickman" Collins rick.collins@XYarius.com Ignore the reply address. To email me use the above address with the XY removed. Arius - A Signal Processing Solutions Company Specializing in DSP and FPGA design URL http://www.arius.com 4 King Ave 301-682-7772 Voice Frederick, MD 21701-3110 301-682-7666 FAX
Reply by ●August 9, 20042004-08-09
"Peter Alfke" <peter@xilinx.com> wrote in message news:BD3D2E1B.7E71%peter@xilinx.com...> ok, I should have said multiply by two. > I just think this argumenting about an extra 12.5%, silly as it may be, is > not worth our combined efforts. > Everybody knows where the factor comes from, most of us disagree with the > reasoning. Grin and bear it. > Do you want to argue about the meaning of "100%" in wine merchandizing? Do > you want to fight the funny factor two in the "%proof" calculation? Orhave> you measured a "2 by 4 inch" piece of lumber? There is lots of fiddling > with numbers going on...If people who market to engineers took to heart what engineers need - accurate information - then this discussion wouldn't involve *any* combined effort. I'd like to think the silicon vendors are more precise than the lumber industry or more informative than a centuries-old form of labeling alcohol content; after all, are the words "percent" and "proof" commonly used *together* in the wine industry? A troy ounce isn't an ounce. We know that. If definitions are provided and spec sheets adhere to those definitions, we're happy. If the spec sheet for a "2 by 4" specifies 2.00" x 4.00", we'll be unhappy with the undersized product - any spec sheet *should* have the actual dimensions and tolerance. Give an engineer precision and there won't be arguments. Complacency with marketing slop - inaccuracies for the sole purpose of justifying a position - may have a place in consumer advertising but is seen as marketing "lies" whenever we LEARN about the BLATANT inaccuracies of the marketing literature. Remember 19" displays (16.2" visible)? Suits forced the industry to properly specify the numbers. I know to go into the rows and columns to get my LUT or LE counts the way that I know they should be specified. It's because I know better now. What impression are we giving the new engineers looking to develop their first FPGA designs? Distorted information is expected from the silicon vendors? That's what they take away once they learn their original estimates were wrong because they didn't KNOW to do conflicting arithmetic on their datasheets. We - as engineers - will never be truly complacent with marketing distortions propagated by our organizations or those we do business with. I think there would be more respect and appreciation garnered from the engineering community if DATASHEETS were fully accurate and didn't include marketing distortions. I can see calling a device a "1Mgate" device where the definition of a gate varies with perspective, but don't tell me there are 12.5 lbs of manure in a 10 lb bag because it smells better to marketing. This is a distortion we continue wrestling with because we cannot change it. We can only work around it as individuals. How about taking up with other marketing slants and use verbiage like "compare with units having 12.5% more resources" or similar sidestepping? Those within the organizations selling FPGAs have to communicate that the numbers are "justified" because it's not right to call your own company's literature misleading. It's easy to "believe" that the numbers are okay because "that's the way it's always been" or that "everyone else is doing it" but it's wrong and there should be internal and external pressures to make the information *accurate* when accuracy is called for. And from where I sit, I feel I'm significantly less frustrated than rickman.
Reply by ●August 9, 20042004-08-09
Oh... and remember years ago when Brand A illustrated 3 registers in their I/Os? My initial work with the datasheets said my timing was good. It was only after getting further into the design that I realized those I/O cells only contained SINGLE registers and couldn't possibly achieve my required performance. Some high-management folks eventually visited us to hear our rants and apologize for the confusion. They not only lost a socket to Brand X for the technical aspects of the design requirements but lost first consideration on most future sockets from a previously "biased" engineer. If I had the "correct" information in the front end of the design cycle, the marketing issues wouldn't have become engineering and financial issues. I would have had stronger respect for the currently offered solutions than I have now. Time heals many things.
Reply by ●August 9, 20042004-08-09
John_H wrote:> Oh... and remember years ago when Brand A illustrated 3 registers in their > I/Os? My initial work with the datasheets said my timing was good. It was > only after getting further into the design that I realized those I/O cells > only contained SINGLE registers and couldn't possibly achieve my required > performance. Some high-management folks eventually visited us to hear our > rants and apologize for the confusion. They not only lost a socket to Brand > X for the technical aspects of the design requirements but lost first > consideration on most future sockets from a previously "biased" engineer. > > If I had the "correct" information in the front end of the design cycle, the > marketing issues wouldn't have become engineering and financial issues. I > would have had stronger respect for the currently offered solutions than I > have now. Time heals many things.Here's a radical thought : Given that 'marketing numbers' have caused, over time, at a minimum annoyance or bemusement, and at a maximum (above) outright customer flight, what about the idea that instead of excusing this silliness, it actually gets fixed, and data sheets get provided with accurate formula for available resource ? If that formula includes a [Real World Calculation] * MFF = HahSoThere we could live with that - even 'grin and bear it'. The MFF ( marketing fiddle factor ) would only be used by the marketdroids, and they alone would boast and compare the right hand side, whilst the designers would use the real world numbers in the multi term equation on the left hand side. Marketing would not have to go 'cold turkey' as their number would still be in the data sheet - just now it is clearly identified :) Or, will we see 'marketing MHz' and 'narketing ns' numbers next..... :( -jg
