Help with FPGA

[Lord Banshee]

seeing that cabling from the CD-ROM to PCI-E will be almost impossible. You might want to rethink about going back to SATA2, even include a cheap/decent 2 SATA2 PCI-X controller and maybe use your design as a 0x RAID. Remember as along as it works it will still be a lot faster than any SATA2 RAID drive, with ns access time and a pure 600MBs is plenty fast.

oh and here is a single spec sheet with pin layout and names
http://www.kentrontech.com/PDF_Files/SP...ets/SODIMMs/512-1GB-D-sodimm,femma.PDF

 

[Stiganator]

So if I want to interface to PCIe I basically need to turn this into a card. What if the "cable is soldered from the cd bay to a pcie card? So there would be less impedance mismatch? The SATA2 will be a last resort...I hate seeing wasted bandwidth.

 

[f95toli]

Doesn't help. Even soldering will give you a mismatch. At these speeds you need to use special launcher structures to get from cable to e.g. 50 ohm striplines.
It is probably possible but the only "easy" way to do it I can think of (assuming 20 GHz bandwidth) would be to use a bunch of 50 ohm semi-rigid coax with SMA connectors at each end followed by SMA launchers. This is of course not a realistic solution (and you would still need computer simulations to make sure that the design works).
As I wrote above: This is microwave engineering; it is VERY different from ordinary
electronics.

I think you will find that the reason why we can't buy the product you are trying to design is that it is
a) Extremely difficult to design
b) Will be VERY expensive.

 

[Stiganator]

has the spec for SATAIII been ratified yet? 400mbps bandwidth right.

 

[nd]

Why not just make it a PCI-E card?

 

[Stiganator]

Well You could, but basically it was tough to fit all that jazz into a cd rom sized thing, fitting it to a card would require more integrated chips and such, but maybe its a good idea. How would i fit 16 so-dimms though?

 

[nd]

Well, I'd say your choices are:

1) Accept that the device will take up 2 slots
2) Use on-board memory chips rather than SO-DIMMs
3) Mount the SO-DIMMs flat against the board rather than perpendicular. Of course, you can't fit as many then.

 

[Stiganator]

Well let's further analyze this.

What are the advantages to having 5GB of bandwidth vs. 400MB?

What is easier to implement, SATA bridge or PCIe bridge?

 

[Lord Banshee]

If you can get 400MB/s sustained not burst that would be fast enough for me. This be more than 4 times faster than my raptor.

And also you know the PCI-E(16x) would be 5GB/s. You would need a 16x2 SLI board to make this work at those speeds. Do you really want to limit the use by only those users? PCI-E x1 (the small one that is suppose to replace PCI cards) is only 250MB/s (i think). SATA sounds better and better to me?

Anyone like to correct me with my numbers please do

 

[nd]

It sounds like the main tradeoff here is SDRAM storage size vs. interface speed. You get the higher SDRAM size if you go with SATA but lose the interface speed you get with PCI-E. I guess it depends on what your goal is with it and what you want to do with it which should dictate the direction you take. Personally, I think the SATA version seems more useful. But then again you seem to care more about the interface speed.

 

[Stiganator]

400MBps sustained is pretty smoking fast, plus the .05 ms access times are off the hitch. Maybe SATA would be ok and seeminingly easier.