Why does it have to be MRAM?
F-RAM or nvSRAM are much more common.
Thanks for the suggestion! I'd totally take FRAM (or any other fast-write technology), but the cheapest Infineon part I can find is FM25V20A-PG, USD4.60 @ digikey.
50Mhz max is not fast, even SPI Psuevdo RAM(old school DRAM) does at least 133Mhz
I mostly just need fast writes to an SPI or I2C memory block to buffer some collected data for processing - 50MHz is plenty fast. Something like the Microchip 23LCV1024-I/ST actually looks pretty good though.