Recently picked up a lightly used Kioxia CM6-v, Lenovo branded and likely their firmware on board. Getting decent performance, but not what I’d expect. When I went to enable write cache, Windows says it isn’t supported. Sure enough, checking CrystalDiskInfo, the features only list SMART & TRIM, VolatileWriteCache is missing.
I feel certain this drive has write cache; the TweakTown review actually says 8GB DRAM cache. I suspect it’s either firmware disabled or just Windows doing Windows things and not recognizing it.
The “Enable write caching on the device” option in Windows lets Windows cache writes in system RAM as opposed to on the SSD’s DRAM, which is already mostly filled up with FTL and some other house keeping structures, very little of the SSD DRAM is used to ever directly cache writes.
As to why you can’t enable that option in Windows, I’m sure it has something to do with the firmware loaded on the drive. I know some OEMs play with firmware to disable this option to reduce FUA command overhead… not exactly sure how they do it though.
I think I’ve heard of people using hacked OS-level drivers to get around the issue too, but I’m not 100% on that.