Spartan 3E vs. Cyclone2

I'm sure you should just be able to tie the upper 16 to ground on a

64-bit controller? Hopefully synthesis will remove most of the registers and logic for those unused data lines.

-- Pete

Piotr Wyderski wrote:

SDRAM

transfers.

Hi Austin,

thanks for your comments.

As I understand you, the logic-fabric is the limiting factor in Spartan

3(E), not the IOs.

I do not need Gbs-speed, just around 600 Mbs will be OK. (So I think I need

300MHz with DDR at the IO.)

Can this be done in the Spartan3(E)? When doing simple tests with D-FFs and T-FFs, I got frequencies in the range from

300 to 600 MHz, not really reproducable. Strange... I have not tried to implement the complete serializer yet. Is there also a limit from the clock-network? In the datasheet I states, that the -4-speedgrade can produce up to 330MHz at the DLL-CLKOUT_FREQ_2X, so I think the clock-network can handle this frequency?

I understand that you want to sell Virtex, but please understand that we want to buy Spartan or Cyclone, even if it are just 1000+ pieces ;-)

Regards,

Thomas

"austin" schrieb im Newsbeitrag news:d1k9tv$ snipped-for-privacy@cliff.xsj.xilinx.com...

:-) Yes, this kludge might work...

Best regards Piotr Wyderski

Thomas,

See comments in line below,

Aust> Hi Austin,

Yes

Yes, that is the use model that we would support.

I do not see why not. We usually use a duty cycle corrected clock out of the DCM at 300 MHz (clk0, and clk180) on two bufgs so you can do all the double data rate stuff at 300 MHz, and then recreate the 600 Mbs at the input, or output pins. The trick is to multiplex this down to 150 MHz ASAP, as 300 MHz data paths are going to be tough to route in the fabric. Mux'ing right next to the IOBs is what is typically done. Is there

That is my understanding, too.

But remeber that this will also probably require a package with some better SI than a pq208 (which definitely is something I would not recommend!).

With the package SI, IO SI, bypassing, etc. you may be better off with a V4 package. The V4 is in a SF363 which is a laminate package with great SI, for example.

Yeah, I know. But if the low cost part can't do it, please do take a look at the V4 parts: I doubt there will be a cost advantage, even in larger quantities. The small V4 devices are a great deal($).