While we don't usually cover SD cards, SanDisk's announcement of 512GB Extreme PRO SD card caught my eye today. There are currently only a couple of 256GB SD cards available and most OEMs have not been able to go above 128GB, so the Extreme PRO is the highest capacity SD card in the world, which really speaks for SanDisk's NAND and packaging expertise. 

SanDisk Extreme PRO SDXC UHS-I Memory Card Specifications
Capacities 128GB, 256GB & 512GB
Read Speed Up to 95MB/s
Write Speed Up to 90MB/s
Warranty Lifetime Limited

The Extreme PRO comes in SDXC format and utilizes UHS-I interface, which is good for up to 104MB/s. As you can see in the table above, the Extreme PRO comes very close to saturating the interface and it carries UHS Speed Class 3 rating, meaning that it is suitable for capturing 4K video. The largest market for the new Extreme PRO SD cards is obviously video professionals because as we transition to 4K video, the need for storage increases substantially, which in turn opens market for larger SD cards.

While SanDisk didn't release any details of the internals, it's pretty safe to assume that the 512GB Extreme PRO consists of 32 x 128Gbit (16GB) dies. The photo above is from SanDisk's 2014 Investor Day presentation where the company claimed that it has the technology for a 32-die SDXC card and with the Extreme PRO the technology has made it into the retail. Since SanDisk/Toshiba doesn't have a 256Gbit NAND die (nobody has one in mass production yet), the only way to achieve 512GB is through a 32-die stack. SanDisk hasn't specified whether the NAND is MLC or TLC, but given that it is a high-end product I'm guessing it is MLC based. 

EDIT: As some of you mentioned in the comments, it seems to be two 16-die stacks instead of a single 32-die stack. SD cards definitely have the room for two die stacks and the photo also shows two 16-die stacks instead of a single 32-die stack. Either way it is impressive since nothing else comes close to the capacity SanDisk offers.

All capacities are available now and the MSRP for the 512GB model is $800, which is certainly high since 512GB SSDs retail for close to $200. However, the Extreme PRO is the only SD card that is available in such a high capacity, so I would say the premium is justified. Stacking more dies on top of each other will always have a negative impact on yield as the wires have to be longer and there are more wires to connect, so the room for errors increases and thus the manufacturing cost goes up as well. 

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  • hojnikb - Thursday, September 11, 2014 - link

    wow 32 dies. Thats insane.
    Although its interesting that they didn't went the same route as they did in the past: Stick more bits per cell. With 4X (as they called their 4bit per cell tech) 256Gbit die would be possible on the same area as 128Gbit MLC. Although i doubt it would be capable of write speeds like that, let alone being pro workload friendly.
  • Kristian Vättö - Thursday, September 11, 2014 - link

    4bpc tech was viable at larger lithographies but at 19nm and below it would be a pain to deal with. It's probably more cost efficient to just dump the not-good-enough-for-SSDs quality NAND to SD cards instead of spending millions in designing yet another die for yet another litho. In the past it was different when SD cards and USB sticks were the #1 application for NAND.
  • hojnikb - Friday, September 12, 2014 - link

    Yeah, that kinda makes sense.
    On the subject of 4bpc; Was there any endurance ratings at the time, when this was available ?
    4bits per cell seems a lot to deal with, even at bigger litographies.
  • Zertzable - Thursday, September 11, 2014 - link

    This is totally insane, 512GB in less than a square inch. I wonder how its performance would compare to a modern hard drive.
  • dananski - Thursday, September 11, 2014 - link

    I get around 90-100MB/sec from my 3TB 5400rpm drives, so roughly the same if their specs are to be believed... :o
  • hojnikb - Friday, September 12, 2014 - link

    random performance (atleast write) is probobly even worse than harddrives, since sd cards aren't suited for that.
  • MrSpadge - Thursday, September 11, 2014 - link

    What about device support? Most smartphones etc. currently claim up to 128 GB SDHC support, as far as I know.
  • DanNeely - Thursday, September 11, 2014 - link

    These are full size SD cards, not micro; so they're not going directly into your phone. However, in most cases the official max capacity on the specsheet is just the biggest card available for testing before the phone was released; but as long as the base SD spec doesn't increment (SD -> SDHC -> SDXC) the higher capacity card will almost always work.

    I suppose we'll find out when they get around to using their gains in density to double uSD capacity to 256GB....
  • mkozakewich - Friday, September 12, 2014 - link

    I've got a full SD card in my phone. The pin structure is about the same, and the interface is the same, so you can get adapters either way. It's a ribbon cable the width of a microSD that you slide into the microSD slot, and then on the other end there's a plastic sandwich with the larger spring-loaded SD slot. The ribbon cable is thin enough to fit in the space between the case and the back cover.
  • fokka - Friday, September 12, 2014 - link

    that's how i destroyed my 128gb kingston sdxc just days after getting it. but then again, i disassembled both sd card and adapter, soldered them together and modded my trusty nexus one so the contraption would fit beneath the battery cover.

    suffice to say i'm happy to call a nice little sandisk 128gb micro sdxc my own since a couple of months.

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