gate capacity between old Virtex-II and newer Virtex-4

Started by July 22, 2009
```I used a Virtex-II  XC2V1000 some time ago. The datasheet says the
capacity is ~1M system gates
with 5,120 slices.

Now, I am looking at a Virtex-4 XC4VLX25. The datasheet says this has
10,752 slices but no longer
gives the equivalent "system gates" capacity.

Question: how do I compare  the capcity of XC4VLX25 to the XC2V1000 ?

is the capacity of XC4VLX25  =2X the capacity of
XC2V1000,
since there are 2X the number of slices?

I don't need the DSP logic, just need to compare system
gates.

Note, the developement board I want to buy comes with
the XC4VLX25,
and I need to make sure this has at least the gate
capacity of the older XC2C1000

-steve
```
```Hello,

The capacity of the device is entirely dependent on your design, not
"system gates." Take your design and synthesize it on a XC4VLX25 to
see if it will fit. I would be very surprised if it doesn't, but
that's the way you can tell. "System gates" are an entirely marketing
phenomenon, not an engineering metric.

- Nathan

On Jul 22, 12:32=A0pm, stevem <steve.martind...@gmail.com> wrote:
> I used a Virtex-II =A0XC2V1000 some time ago. The datasheet says the
> capacity is ~1M system gates
> with 5,120 slices.
>
> Now, I am looking at a Virtex-4 XC4VLX25. The datasheet says this has
> 10,752 slices but no longer
> gives the equivalent "system gates" capacity.
>
> Question: how do I compare =A0the capcity of XC4VLX25 to the XC2V1000 ?
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0is the capacity of XC4VLX25 =A0=3D2X the c=
apacity of
> XC2V1000,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0since there are 2X the number of slices?
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0I don't need the DSP logic, just need to c=
ompare system
> gates.
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 Note, the developement board I want to buy co=
mes with
> the XC4VLX25,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 and I need to make sure this has at least the=
gate
> capacity of the older XC2C1000
>
> =A0 =A0 -steve

```
```On Jul 22, 4:14=A0pm, Nathan Bialke <nat...@bialke.com> wrote:
> Hello,
>
> The capacity of the device is entirely dependent on your design, not
> "system gates." Take your design and synthesize it on a XC4VLX25 to
> see if it will fit. I would be very surprised if it doesn't, but
> that's the way you can tell. "System gates" are an entirely marketing
> phenomenon, not an engineering metric.
>
> - Nathan
>
> On Jul 22, 12:32=A0pm, stevem <steve.martind...@gmail.com> wrote:
>
> > I used a Virtex-II =A0XC2V1000 some time ago. The datasheet says the
> > capacity is ~1M system gates
> > with 5,120 slices.
>
> > Now, I am looking at a Virtex-4 XC4VLX25. The datasheet says this has
> > 10,752 slices but no longer
> > gives the equivalent "system gates" capacity.
>
> > Question: how do I compare =A0the capcity of XC4VLX25 to the XC2V1000 ?
>
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0is the capacity of XC4VLX25 =A0=3D2X the=
capacity of
> > XC2V1000,
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0since there are 2X the number of slices?
>
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0I don't need the DSP logic, just need to=
compare system
> > gates.
>
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 Note, the developement board I want to buy =
comes with
> > the XC4VLX25,
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 and I need to make sure this has at least t=
he gate
> > capacity of the older XC2C1000
>
> > =A0 =A0 -steve
>
>

Going from Virtex 2 to Virtex 4, the LUT sizes and LUT to Flip-flop
ratio remains the same.  So probably easiest to count the flip-flops
on the two chips for a rough estimate.  However if your design is
memory (block RAM) or I/O limited you'll need to probe deeper into
the architectural differences.  Also V4 is sufficiently faster that
you may be able to save logic resources by using higher clock
rates and narrower data paths, or more logic levels between
pipeline stages.  As noted, this is a rough estimate YMMV.
Best bet as Nathan pointed out is to port your code and look
at the results.  DON'T look at the "logic elements" column
in the V4 datasheet, this is an inflated number.  Count the flops!

regards,
Gabor
```
```On Jul 22, 12:32=A0pm, stevem <steve.martind...@gmail.com> wrote:
> I used a Virtex-II =A0XC2V1000 some time ago. The datasheet says the
> capacity is ~1M system gates
> with 5,120 slices.
>
> Now, I am looking at a Virtex-4 XC4VLX25. The datasheet says this has
> 10,752 slices but no longer
> gives the equivalent "system gates" capacity.
>
> Question: how do I compare =A0the capcity of XC4VLX25 to the XC2V1000 ?
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0is the capacity of XC4VLX25 =A0=3D2X the c=
apacity of
> XC2V1000,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0since there are 2X the number of slices?
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0I don't need the DSP logic, just need to c=
ompare system
> gates.
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 Note, the developement board I want to buy co=
mes with
> the XC4VLX25,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 and I need to make sure this has at least the=
gate
> capacity of the older XC2C1000
>
> =A0 =A0 -steve

The part number gives you a rough indication of the relative amount of
available logic.
Within one family, this indication is fairly accurate.
Even between Virtex families it may be good enough for a first
evaluation, if you understand that Xilinx dropped two zeros when
moving from Virtex 2 to the newer families Virtex-4, -5, and -6.
That means your XC4VLX25 is roughly equivalent to a XC2C2500.
(When numbers got too large, the French and also the Finns at one time
dropped two zeros from their currency, "vive le nouveau franc")
Peter Alfke
```