jleslie48
Guest
Thu Sep 22, 2011 9:50 pm
the xilinx says it has 500,000 gates,
the altera says it has
22,320 Logic elements (LEs)
594 Embedded memory (Kbits)
66 Embedded 18 x 18 multipliers
4 General-purpose PLLs
so are these two fpga's comparable in size/ computing power/ ability
to support the same VHDL or what?
backhus
Guest
Fri Sep 23, 2011 1:40 pm
On 22 Sep., 21:50, jleslie48 <j...@jonathanleslie.com> wrote:
Quote:
the xilinx says it has 500,000 gates,
the altera says it has
22,320 Logic elements (LEs)
594 Embedded memory (Kbits)
66 Embedded 18 x 18 multipliers
4 General-purpose PLLs
so are these two fpga's comparable in size/ computing power/ ability
to support the same VHDL or what?
Hi,
The comparision of two types of FPGAs is not simple.
Your statement about the Xilinx device is oversimplified.
It is useful for comparisions of Xilinx devices of the same family,
but nothing beyond that.
Also this method has already been kind of "dropped" for more recent
device families.
For all Xilinx devices there are also informations available that are
more comparable to the informations you have listed for the altera
device.
e.g for the S3E-500:
1,164 CLBs = 4,656 Slices of 2 LUts 2FFs and some Carry logic
360K BRAM
20 Multipliers
4 DCMs
And for the othere informations consult the datasheets of both
devices.
VHDL is always the same, but the tools may have special support, that
can cause incompatibilities.
So the correct usage of some HDL is more or less depending on the
skills of the engineer that is working with it.
Have a nice synthesis
Eilert
John Adair
Guest
Fri Sep 23, 2011 2:57 pm
As already said the comparision is not simple but a starting point is
a comparision of LUTs and flipflops. Even then you need to take
account of variation in LUTs e.g. Spartan-6 has a 6 ip LUT which might
be comparible to 2 x 4 ip LUT in a Spartan-3.
If you design needs a lot of ram e.g. for video or multipliers for DSP
these are also things to look at.
Ultimately if your design, or part of it, is available you can always
do a trial build. Both Xilinx and Altera have free versions of their
tools which you could a trial even if the size of device you are
interested in isn't supported in those versions just try in for a
smaller one and get a logic size out of that.
John Adair
Enterpoint Ltd. - Home of the XC6SLX150 X2 Coprocessor Module.
On Sep 22, 8:50 pm, jleslie48 <j...@jonathanleslie.com> wrote:
Quote:
the xilinx says it has 500,000 gates,
the altera says it has
22,320 Logic elements (LEs)
594 Embedded memory (Kbits)
66 Embedded 18 x 18 multipliers
4 General-purpose PLLs
so are these two fpga's comparable in size/ computing power/ ability
to support the same VHDL or what?
Ed McGettigan
Guest
Fri Sep 23, 2011 5:57 pm
On Sep 22, 12:50 pm, jleslie48 <j...@jonathanleslie.com> wrote:
Quote:
the xilinx says it has 500,000 gates,
the altera says it has
22,320 Logic elements (LEs)
594 Embedded memory (Kbits)
66 Embedded 18 x 18 multipliers
4 General-purpose PLLs
so are these two fpga's comparable in size/ computing power/ ability
to support the same VHDL or what?
The XC3S500E (this is an older family) is about 50% of the resources
as a EPC4CE22
XC3S500E EP4CE22
LE - 10,476 22,320
Memory - 360K 594K
Mult-18x18 - 20 66
PLL/DCM - 4 4
Max IO - 232 150
The XC3S1200E (same family) is closer in resources and the next size
up is about 50% larger:
XC3S1200E EP4CE22
LE - 19,512 22,320
Memory - 504K 594K
Mult-18x18 - 28 66
PLL/DCM - 4 4
Max IO - 304 150
The same modern family from Xilinx as an EPC4CE22 is the Spartan-6
line:
XC6S25 EP4CE22
LE - 24,051 22,320
Memory - 936K 594K
Mult-18x18 - 38 66
PLL/DCM - 6 4
Max IO - 266 150
Ed McGettigan
--
Xilinx Inc.
jleslie48
Guest
Fri Sep 23, 2011 6:18 pm
On Sep 23, 11:57 am, Ed McGettigan <ed.mcgetti...@xilinx.com> wrote:
Quote:
On Sep 22, 12:50 pm, jleslie48 <j...@jonathanleslie.com> wrote:
the xilinx says it has 500,000 gates,
the altera says it has
22,320 Logic elements (LEs)
594 Embedded memory (Kbits)
66 Embedded 18 x 18 multipliers
4 General-purpose PLLs
so are these two fpga's comparable in size/ computing power/ ability
to support the same VHDL or what?
The XC3S500E (this is an older family) is about 50% of the resources
as a EPC4CE22
XC3S500E EP4CE22
LE - 10,476 22,320
Memory - 360K 594K
Mult-18x18 - 20 66
PLL/DCM - 4 4
Max IO - 232 150
The XC3S1200E (same family) is closer in resources and the next size
up is about 50% larger:
XC3S1200E EP4CE22
LE - 19,512 22,320
Memory - 504K 594K
Mult-18x18 - 28 66
PLL/DCM - 4 4
Max IO - 304 150
The same modern family from Xilinx as an EPC4CE22 is the Spartan-6
line:
XC6S25 EP4CE22
LE - 24,051 22,320
Memory - 936K 594K
Mult-18x18 - 38 66
PLL/DCM - 6 4
Max IO - 266 150
Ed McGettigan
--
Xilinx Inc.
Thanks for all the thoughts on this. I realize these things are
still in their infancy, but the "computing power" in general terms
should be comparable between different brands of FPGA's. I'm not
looking for accuracy to 4 decimal places, but just a ballpark
expectation. Ed's values seem to give good apples to apples values
for comparision.
My first project with fpga went well enough until I tried to fit it
onto a cpld chip only to find that the CPLD chip was 1/1000th the size
of the spartan 3E I was using as a development target. When
something is 3 orders of magnitude different, I should be able to tell
reasonably easy.
So my walkaway from this thread is: in the future, a better "marker"
for size is LE's instead of gates.
Martin Thompson
Guest
Mon Sep 26, 2011 8:02 am
jleslie48 <jon_at_jonathanleslie.com> writes:
Quote:
So my walkaway from this thread is: in the future, a better "marker"
for size is LE's instead of gates.
Certainly better, but in no way sufficient :)
That'd be like choosing a micro based on DMIPS with no regard for
peripherals, IO count, on-chip memory (volatile and
non-volatile)... It's just that when you're already used to choosing
micros - for your first-pass shortlisting - you already trade all those
off without thinking conciously about it.
Cheers,
Martin
--
martin.j.thompson_at_trw.com
TRW Conekt - Consultancy in Engineering, Knowledge and Technology
http://www.conekt.co.uk/capabilities/39-electronic-hardware
backhus
Guest
Mon Sep 26, 2011 8:28 am
On 23 Sep., 18:18, jleslie48 <j...@jonathanleslie.com> wrote:
Quote:
On Sep 23, 11:57 am, Ed McGettigan <ed.mcgetti...@xilinx.com> wrote:
On Sep 22, 12:50 pm, jleslie48 <j...@jonathanleslie.com> wrote:
the xilinx says it has 500,000 gates,
the altera says it has
22,320 Logic elements (LEs)
594 Embedded memory (Kbits)
66 Embedded 18 x 18 multipliers
4 General-purpose PLLs
so are these two fpga's comparable in size/ computing power/ ability
to support the same VHDL or what?
The XC3S500E (this is an older family) is about 50% of the resources
as a EPC4CE22
XC3S500E EP4CE22
LE - 10,476 22,320
Memory - 360K 594K
Mult-18x18 - 20 66
PLL/DCM - 4 4
Max IO - 232 150
The XC3S1200E (same family) is closer in resources and the next size
up is about 50% larger:
XC3S1200E EP4CE22
LE - 19,512 22,320
Memory - 504K 594K
Mult-18x18 - 28 66
PLL/DCM - 4 4
Max IO - 304 150
The same modern family from Xilinx as an EPC4CE22 is the Spartan-6
line:
XC6S25 EP4CE22
LE - 24,051 22,320
Memory - 936K 594K
Mult-18x18 - 38 66
PLL/DCM - 6 4
Max IO - 266 150
Ed McGettigan
--
Xilinx Inc.
Thanks for all the thoughts on this. I realize these things are
still in their infancy, but the "computing power" in general terms
should be comparable between different brands of FPGA's. I'm not
looking for accuracy to 4 decimal places, but just a ballpark
expectation. Ed's values seem to give good apples to apples values
for comparision.
My first project with fpga went well enough until I tried to fit it
onto a cpld chip only to find that the CPLD chip was 1/1000th the size
of the spartan 3E I was using as a development target. When
something is 3 orders of magnitude different, I should be able to tell
reasonably easy.
So my walkaway from this thread is: in the future, a better "marker"
for size is LE's instead of gates.
Hi,
and again you are about to make the same mistake as before.
Don't try to nail down the capabilities of such complex devices as
FPGAs to a single number.
And don't forget to include the skills of the engineer(s) in your
calculation.
Have a nice synthesis
Eilert
Guest
Mon Sep 26, 2011 11:48 am
On Thursday, 22 September 2011 20:50:18 UTC+1, jleslie48 wrote:
Quote:
the xilinx says it has 500,000 gates,
the altera says it has
22,320 Logic elements (LEs)
594 Embedded memory (Kbits)
66 Embedded 18 x 18 multipliers
4 General-purpose PLLs
so are these two fpga's comparable in size/ computing power/ ability
to support the same VHDL or what?
*Meaningful* "apples to apples" comparison of this type is impossible. Not only across vendors, but also across different architectures from the same vendor, where the "units" are supposedly the same.
You start out by considering gates, LEs and slices, which get you nowhere useful -- it really doesn't give you any good indication on how efficient your design is going to be mapped into the architecture, for example. (Counting FFs and LUTs isn't helpful because there are restrictions on how they are used due to bundling). Then the next thing is to try targeting your design for different architectures. But are the results meaningful? Did you lose performance due to a generic design? Did you use the same software? Same version? Same settings? Did you correctly convert architecture specific primitives (BRAMs, DSPs, etc.) across architectures? Does your code happen to be optimized for one architecture but not the other? It's difficult for me to imagine hearing satisfactory answers to some of these questions.
So what *can* you do? Look at the context of your application: your needs, your experience, and your budget. Which architecture has hard cores for what you are trying to build? Which vendor supplies readily available soft cores ("IP") that you need? Do you have more experience with one of the vendors? Did one of the vendors give you a better deal? Which device has a cheap dev kit you could use? Are free tools available for your target device? If you're a student, which vendor is your University using for their classes? And so on...
Once you answer those, that initial comparison wouldn't seem so important.
glen herrmannsfeldt
Guest
Mon Sep 26, 2011 9:12 pm
jleslie48 <jon_at_jonathanleslie.com> wrote:
Quote:
the xilinx says it has 500,000 gates,
In the olden days (before BRAM and embedded multipliers) there was
some use for this number, though very little. A little less useful
than MIPS (Meaningless Indicator of Processor Speed) is of serial
CPU performance.
But now it includes the logic in BRAMs and multipliers, and anything
else that they add on. Often your design doesn't use these additional
resources in the exact proportion that they are supplied, and so
the extras go to waste. (Like CPU cycles while waiting for I/O.)
Quote:
the altera says it has
22,320 Logic elements (LEs)
594 Embedded memory (Kbits)
66 Embedded 18 x 18 multipliers
4 General-purpose PLLs
This allows you to separately determine the logic, block memory,
and block multplier resources. You alse need to know the size of
an LE to compare with anything other than another device in the
same family.
Quote:
so are these two fpga's comparable in size/ computing power/ ability
to support the same VHDL or what?
Is a 200MHz Pentium faster than a 250MHz PowerPC 620?
--glen
