Hynix 48-GB Flash MCP

Hal_Porter writes to let us know that the third-largest NAND chip maker, Hynix, has announced they have stacked 24 flash chips in a 1.4mm thick multi-chip package. It's not entirely clear from the article whether the resulting 48-GB device is a proof of concept or a product. The article extrapolates to 384 GB of storage in a single package, sometime. Hal_Porter adds: "It's not clear if it's possible to write to them in parallel — if so the device should be pretty damn fast. The usual objection to NAND flash as a hard drive replacement is lifetime. NAND sectors can only be written 100,000 times or so before they wear out, but wear leveling can be done to spread writes evenly over at least each chip. I worked out that the lifetime should be much longer than a typical magnetic hard disk. There's no information on costs yet frankly and it sounds like an expensive proof of concept, but it shows you the sort of device that will take over from small hard disks in the next few years."

Comments

48 GB = 384Gb

[sirket]

The article does not extrapolate to 384 GB of storage- they extrapolate to 384 Gb of storage which is 48 GB of storage. bits != bytes.

Re:Why only 100,000 times

[jandrese]

It's due to the way Flash works. A flash bit is basically a conductor surrounded by an insulator. To store a bit, you apply a large charge to the insulator to increase the charge of the conductor, basically your burning through the insulator to get your charge though. Once it is on there, to read the charge you have to apply another large charge to the insulator and see if the resultant charge is n or n + m. The m factor comes from latent charge on the conductor.

Anyway, the upshot of this is that because you have to constantly burn charge through the insulator to use the part, eventually you basically burn out the insulator and cause it to leak charge. Once it starts leaking, you lose your stored bits and the part is useless.

Re:Why only 100,000 times

[networkBoy]

Flash is rated in erase cycles, not write cycles. Erase is the most damaging event to the tunnel oxide layer in the device, which is why they fail.
Flash Cell stackup (same for NOR and NAND, the interconnection of cells determines what type of array it is):

G - gate (metal)
ONO - Oxide/Nitride/Oxide layer
FG - Floating Gate (Poly)
tOx - Tunnel Oxide (very thin)
Si - wafer (NPN/PNP wells) -nB