Re: 400 Mb/s ADC

Jeff Peterson wrote:

> We are building a new radio telescope called PAST
> (http://astrophysics.phys.cmu.edu/~jbp/past6.pdf)
> which we will install at the South Pole or in Western China.
>
> To make this work, will need to sample (6 to 8 bit precision) dozens
> of analog voltages at 400 Msample/sec and feed these data streams into
> PCs. One PC per sampler.
>
> The flash ADCs we need are available (Maxim), but we are finding it
> difficult to get the data into the PC.
>
> One simple way would be to use SCSI ultra640, but so far I have not
> found any 640 adapters on the market.  Is any 640 adapter available?
> anything coming soon?
>
> or we could go right into a PCI-X bus.  has anyone out there
> done this at 400 Mb/s?  is this hard to do? FPGA core liscense
> for this seems expensive ($9K), with no guarentee of 400 mByte rates.

The first thing I would think of would be to buffer it and then read it 
later.  You don't say how long this data stream will be, or if this is a 
peak rate with a much lower average rate.  Does it have to go to disk at 
that rate?

You could collect the samples into 64 bit words and write then into 
SDRAM at 40 or 50 MHz.

If it has to go to disk at that rate, I would work on the hardware to 
get it onto the disk without a processor in between.

-- glen