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New Serial ATA Standards Target SSDs, Tablets
crookedvulture writes "SATA-IO has devised a couple of new storage interfaces optimized for solid-state drives. To serve high-performance SSDs that are fast approaching the 6Gbps ceiling imposed by the current Serial ATA specification, the SATA Express standard will meld the Serial ATA software stack with PCI Express to offer up to 16Gbps of bandwidth. SATA Express isn't expected to be completed until the end of the year, but the new uSSD standard looks to be ready for prime time. Designed for tablets and ultraportables, uSSD sticks with current 6Gbps speeds but ditches traditional Serial ATA connectors, allowing SSD controller chips to be soldered directly to motherboards. SanDisk already has a 128GB uSSD primed for ultrabooks."
They already have. SATA-over-mPCIe has been around since the original eeePC - the SATA SSD it uses was mounted in a mini-PCIe looking slot. But it wasn't, since it ran SATA signals over it.
A more recent example started since the 2010 Macbook Airs which had a bog-stadanrd SATA based SSD in something that looked like a mini-PCIe slot - again, it was SATA signals wired to the slot.
This spec just makes it official so everyone can build adapters, SSDs and laptops based on it and be standardized across the entire line. otherwise you'd have formfactor issues, possible pinout issues, etc.
At those kinds of speeds, you start talking about a system that goes from completely off to completely on in a second. When you want to hibernate, you dump everything in memory over to the disk. When you turn back on, you take a moment to find the disk, and pull the entire memory image back over. There is no boot, there is no shutdown. You only need enough memory to handle the actual in-use programs, and anything else could be painlessly paged out, meaning you never have to close programs.
It's an order of magnitude slower than RAM, but an order of magnitude faster than hard disks. Right smack in the middle in order to offer all sorts of cool little tricks.
It would probably be most accurate to think of this "uSSD" as a faster, more PC-architecture-oriented version of the "eMMC" JEDEC standard for soldering flash directly onto a motherboard, with a lower board space, pin count, and controller requirement than raw flash chips.
"eMMC", which is basically an MMC card's guts in a BGA package, is already quite popular in things like cellphones(ever wonder why some cellphones filesystem names suggest that they have an MMC card that they don't really? It's because they do, in software terms...) "uSSD" will, presumably, be the big brother of that standard, putting SATA signals and power over a standardized BGA arrangement, rather than using MMC signals and power...
Because:
-there are thousands of chips out there that have a built-in SATA interface
-BIOSes and kernels already know SATA, and developers are already used to working with it
-MMC/SD/eMMC doesn't come close to the throughput of SATA
-manufacturers don't like vendor lock-in, and SATA is the most popular non-embedded SSD interface
Hard drives in PCs start out with a proprietary interface by Segate that becomes a defacto standard. It needs an interface controller to tell the drive what to do. That controller sits on the ISA bus. Speeds increase, drives become bigger, they move the controller onto the hard drive. The ISA bus still connects to the controller, and the controller still tells the drive what to do, it's just that we now call the connection between the motherboard and the controller the IDE (integrated drive electronics) bus, but it's still the ISA bus. Speeds increase, now we increase the speeds of the IDE bus and add features, it slowly moves away from the ISA bus as the IDE controllers get more complicated. Speeds increase and having that bus as a parallel interface doesn't cut it, so we invent SATA. A SATA controller sits on the PCI bus and tells the drive's controller what to do. Speeds increase and now we're back to directly connecting the hard drive to the PCI (now PCI-E, but same parallel to serial transition) bus. -- Full Circle.