Now I am really confused!

[rickman]

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

 

[Peter Alfke]

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

 

[rickman]

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

 

[Tim]

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

Our 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"

 

[Peter Alfke]

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

 

[General Schvantzkoph]

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 FAX

Peter 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.

 

[rickman]

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

 

[John_H]

"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? Or
have
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.

 

[John_H]

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.

 

[Jim Granville]

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

 

[Jerry]

"Tim" <tim@rockylogic.com.nooospam.com> wrote in message
news:cf8jpk$82o$1$8302bc10@news.demon.co.uk...

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

Our 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"


Anybody old enough to remember Radio Shack's spec on the stereo amps? 150

WATTS to
us means out put power to speakers. From Radio Shacks spec it was input
power on the AC side.

 

[Hal Murray]

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 ?

Would it do any good if several people wrote (paper) letters to
the marketing dept? Mayve we could convince some of them to
use real numbers and brag about having honest info. They could
even make up a fancy name for it. or

I think it terms of LUTs/FFs so an accurate table is what I'm looking
for. Extra columns for RAM, multipliers, and such would be handy.

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.

 

[Paul Leventis (at home)]

In the meantime, Altera has jumped on this bandwagon and they multiply
their
ALE numbers by 1.25.

Jumping to our defense on this one, we clearly state the number of Adaptive
Logic Modules (ALMs) in our Stratix II literature, and a give a separate
"Equivalent Logic Element" count. We use 2.5 LEs per ALM to provide our
customers with a way to easily compare the logic capacity of Stratix and
Stratix II devices. This is not smoke and mirrors -- the Stratix II ALM is
a radically different logic structure. The number of ALMs/LE will differ
from design to design, but over 100+ user designs we found that 2.5 was a
reasonable estimate.

Regards,

Paul Leventis
Altera Corp.

 

[Nicolas Matringe]

John_H a écrit:

Oh... and remember years ago when Brand A illustrated 3 registers in their
I/Os?

I do!
I'm still angry with them about that one (though they actually put 3
registers in their latest chips)

--
____ _ __ ___
| _ \_)/ _|/ _ \ Adresse de retour invalide: retirez le -
| | | | | (_| |_| | Invalid return address: remove the -
|_| |_|_|\__|\___/

 

[rickman]

"Paul Leventis (at home)" wrote:

In the meantime, Altera has jumped on this bandwagon and they multiply
their
ALE numbers by 1.25.

Jumping to our defense on this one, we clearly state the number of Adaptive
Logic Modules (ALMs) in our Stratix II literature, and a give a separate
"Equivalent Logic Element" count. We use 2.5 LEs per ALM to provide our
customers with a way to easily compare the logic capacity of Stratix and
Stratix II devices. This is not smoke and mirrors -- the Stratix II ALM is
a radically different logic structure. The number of ALMs/LE will differ
from design to design, but over 100+ user designs we found that 2.5 was a
reasonable estimate.

I'm not trying to take sides in this, but my original post was about how
the data sheet defined "Logic Cells" one way and then counted them
another. If the data sheet clearly says that the numbers are "adjusted"
with some fudge factor, that is not so big a deal. But if you define an
LC one way and count it another, that is just not honest.

Every FPGA has extras in them which extend the capacity of the LUTs.
But when I am trying to count LUTs in my block diagram to see how large
a part I will need, I already have all the "fudge factors" I can handle,
I don't need more from the data sheets!

--

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

 

[Peter Alfke]

The deux chevaux were really a measure of taxation, had little to do with
engineering horsepower (which has little to do with the performance of a
horse).
The Brits used a similar strange taxation measurement.
Peter Alfke

Our 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"


Anybody old enough to remember Radio Shack's spec on the stereo amps? 150
WATTS to
us means out put power to speakers. From Radio Shacks spec it was input
power on the AC side.