Why Spartan-3e is the best

Why Spartan-3e is the best
==================
Antti Lukats
4.Nov 2005

(I was asked about why I think so in private, but I think
my response could have more general interest so I am posting
the reply to c.a.f.)

-------------------------------------------------------------

At first look there differences between S3 and S3e may not
be so significant however there are several small things
that make Spartan-3e my fist choice (from current low-cost
RAM based FPGA offerings).

1) as Spartan-3 was the first Xilinx silicon on new technology
its kind of logical that Xilinx has fixed in Spartan-3e some
issues related to the use of the new technology. So even if those
are minor, there are still chances that S3e is somewhat better
simply because Xilinx has had more experience with the technology
being used.

2) pricing is promised a little lower, this is not so big deal,
but still, its pretty much logical to prefer silicon with best
price/performance ratio.

3) S3e configuration options are WAY superior over all other RAM
based FPGAs currently in production. S3e is the only FPGA that:

* can load not only from SPI Flash but also from Atmel Dataflash
meaning that a it is the only FPGA around that can directly use
an MMC (Atmel MMC form factor packaged 2/4/8 MByte Dataflash cards)
like Flash card as its main configuration media. So a design with
S3e and MMC Card socket can boot from the removabale flash media
card. Note that the MMC Card socket inserion switch could overide
the 'enable' of the additional on board memory so the SoC loaded
from the inserted into socket Dataflash card could copy a new
bitstream and OS image onto onboard flash, so next 'boot' without
card inserted could come from on board DataFlash. Nice little
feature.

* can load from Parallel Flash, just like the oldies (eg Xilinx first
FPGA's).
This is VERY good feature as it allows cheap Flash ROMs to be used for both
config and OS image.

* has 'multi boot' option. In Parallel Flash loading mode S3e can
request its own reconfiguration from alternative image.

---

compared to S3, S3e configuration interface allows the use
of SPI or Platform Flash for firmware storage without the
use of extra FPGA IO pin workaround.

S3e configuration is still way less flexible than I could
have designed, but its still the industries best at the moment.


4) S3e has LVDS input onchip termination. I have to admit that
I first found the low cost LVDS onchip termination feature in
Altera Cyclone-II but then I did re-found it in Spartan-3e as
well. It may not so sound like a nig deal, but its a nice
little additional feature that may save some PCB space.

5) Some nice new (compared to other Spartan FPGAs)
package combinations like:
*Largest fabric in VQ100
*Largest fabric in chip-scale package
*Largest fabric in FT256
*Largest fabric in non-BGA package

5) S3e starterkit from Avnet is selling at almost all
time low price of 69USD. (Futre did sell Cyclone kits
for $49 for a while but that kit did not look anything
I would spend money for). To get an eval board with
HS USB chip + FPGA for total cost of $69? Real candy.

6) There are possible some other nice new features
I have not discovered yet :)


Antti Lukats


.

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