I have the MSI Neo4 motherboard (nforce4 chipset) with latest Nforce IDE drivers, they work fine with my 1620 which I sold yesterday.
My OEM 1640 from ncix.com arrived today (ordered yesterday) and it came with BSHB firmware, I downloaded BSJB and flashed it but it hang at the end of the flashing progress (keyboard and mouse etc don't response) the led on the 1640 stopped flashing but I can open/close tray, I waited 30 minutes, nothing, so oh well maybe RMA time, so I reboot PC and it hanged at bios, ie can't detect the 1640 so I unplugged the IDE cable from the 1640 and all boot well, I turned off PC and replugged the IDE cable to the 1640 and bios detected the 1640 and after Windows XP loaded I check and it said the 1640 is now with BSJB bios. I then uninstalled Nforce4 IDE drivers and reflashed BSJB and all went well ie no hanging at the end of flash, I reflashed it again in safe mode to make sure and now all went well, tested burn a disk and it works fine.
Sharing this story to those who also have nforce4 IDE drivers so that they may be precaution before flashing firmware with the 1640.
One thing with Windows IDE drivers is that it doesn't see my SATA HDD as a SATA drive but a IDE UDMA 6 HDD, no SATA channel in Device manager but two IDE controller two Primary channel and two secondary channel, before it was a Nvida SATA controller with Primary and Secondary channel and a Nvida IDE controller with Primary and Secondary channel.