Well, this one is a bit of a gamble. Unlike SRAM, it seems like there hasn't been a need in the NOR Flash market for any sizable increases. The 4 MB LH28F320BFHE-PBTLZ2, organized as 2 MBit x 16, has a read cycle time of 80 ns and a top operational speed of 5 MHz. The fastest replacement I can find is made by Spansion.The S29JL032J60TFI020 and has a read cycle time of 60 ns but also a top operational speed of 5 MHz. So, same signaling rate and lower latency? Granted it's 25% though I was disappointed to find this out.
"But it's Flash! You don't need it to be faster."
Yeah, well the way the TI calculators are setup your effective harddrive is the "ROM". Execution cannot happen from ROM but if you have a lot of programs, albeit games, or TI's Flash Apps, you drop from reading and writing at 12 MHz to 5 MHz and that has always been noticeable. That said, 60 ns latency to 80 ns latency might increase the bandwidth as long as the OS isn't hardcoded with delays for accessing the ROM.
With that said, some other complaints or problems with overclocking is boot errors so decreasing the latency spread of the Flash and SRAM wouldn't be a bad thing. I do wish it wouldn't cost $2.85 for such a meager upgrade. I does look like it'll consume between 33% and 60% less current and it's standby current is an order of magnitude better.
That all said, I'm not sure if it'll work. The Spansion chip allows reading while writing data and other configurable options. Honestly, without knowing all that is happening I won't know if this chip is compatible.
Lastly, I check the pinout. Probably should've done this first as they differ sigificantly. Too much so I'm going to forgo 'upgrading' this IC.