How many AltAccumulates?

Hi,

I am looking to instantiate 48000 64bit AltAccumulates in a Cyclone 3 device running at a 200MHz data input rate into the FPGA i.e this is the frequency required to switch between them, although each accumulator will only be updated at a rate of approx 10KHz.

Am I being unrealistic?

I can achieve much the same thing using the FPGA internal memory and adders, but it requires more internal memory than the largest cyclone 3 devices provide. I can get the results I want from Stratix devices, but the cost penalty is unacceptable.

I realise I can use external DDR2, but I only require 3 MBits, so it seems rather wasteful, leave alone the increased complexity. Board space is also premium.

I have tried implementing the required memory in logic and Quartus runs out of memory despite the /3GB setting in windows and stops - generally after several hours of trying.

The biggest issue I have with the Altaccumulate is the time it takes to compile - I haven't managed to get it to complete yet - the longest I have left it is 28 hrs. To instantiate 2400, 1/20th of what I need takes 3 hrs on a 3 gig dual core win xp with 4GB of Ram.

I'd be grateful for any advice / suggestions

Many Thanks

Duke