cRIO DRAM (non-FPGA accessible) and Host Memory Buffer

[cbutcher]

In the search for a large block of memory on a cRIO-9045 or 9149 expansion chassis, I see the datasheets specify 2GB and 256MB respectively of DRAM.

Unlike (for example) the 9049, which explicitly distinguishes "FPGA memory (DRAM)" and "Processor memory", there is no such distinction in the 9045 or 9149 specifications - as a result, I conclude that these targets cannot access the memory described there via e.g. DRAM-backed memory items as described here: FPGA Memory Items, Configuring DRAM with FPGA Memory Items.

I tried to make use of the Xilinx memory block Express VIs, but it seems these are only for use with BRAM (which can already be accessed using Memory Items more readily).

I then found this link: Host Memory Buffer Overview and then Host Memory Buffer for CompactRIO. This appears more promising - here it seems the memory being addressed is that of the "host", which would appear to be what's listed (non-explicitly) in the 9045 and 9149 specifications.

The overview link describes the devices initially supported in 2017, which does not include cRIO-903x or 904x devices (the latter didn't exist in 2017 anyway...)

However, the forum link from a couple of years earlier (NI Labs) suggests that the 903x is 'supported' (or rather, that it is compatible. Support is probably the wrong word given the context).

Does anyone know if

a) this is a suitable memory source to try get a larger block than the available BRAM for use with FPGA code?

and b) if the 9045 (or even better, the 9149, but I'm less hopeful there) can be used in this fashion?

c) newer versions of CompactRIO drivers might have expanded the supported devices? Or are likely to expand in a future version? (I currently have CompactRIO v21.0.0 installed, so I guess the currently supported devices don't extend to 9045).

Regarding b), I'd guess perhaps I would need to compile the FPGA C interface as described in the NI Labs forum link and then manually install, since it doesn't appear to be a supported target in the CompactRIO drivers.