If you’ve been following the roller-coaster ride that constitutes the global semiconductor memory market, then you’re probably looking over the shoulders of as many memory analysts as possible, trying to find one whose crystal ball isn’t cracked, fused, melted, or blackened. Memory analyst Lane Mason recently spent some time at Denali Software and recorded a Webcast with his overview of recent events in the global memory arena, his view of today’s status, and his forecasts for what is to come. Lane’s been following the memory market for well more than a decade and his counsel is solid. See and listen to his report here.

Hot on the heels of Numonyx’ announcement of two commercial PCM (phase-change memory) products (see “Numonyx 128-Mbit serial- and parallel-I/O PCM non-volatile memories now available in volume”), Samsung announced on April 28 that it plans to ship a device “later this quarter” that integrates DRAM and PCM devices into a multichip package (MCP). Samsung has named its flavor of PCM “PRAM” for “Phase-change RAM.” The PRAM in this MCP is a 512-Mbit device and its intended use is for replacing the NOR Flash memory that currently stores code for a Smartphone. Samsung claims that the PCM used in this new device is three times faster than the NOR Flash it replaces.

Perhaps just as important, both the PCM and DRAM chips in the announced MCP employ the LPDDR2 interface. Consequently the MCP need only present one LPDDR2 interface and one set of pins to the outside world, while distributing the LPDDR2 signals to the two chips internally. In addition, the Smartphone SOC or ASSP only needs one LPDDR2 interface and one set of interface pins to connect to the announced device. These pin efficiencies are no doubt possible because of the LPDDR2-NVM interface extensions specifically created to allow non-volatile memory to easily coexist with LPDDR2 memories (see “State-of-the-Art in Low-Power Memory: Denali’s MemCon”). Although the LPDDR2-NVM spec was developed for Flash devices, it appears to work just as well for PCM devices.

Note that Samsung’s announcement differs from the Numonyx announcement of commercial devices in one significant way. Numonyx announced the immediate availability of its two PCM devices in production volume and included the immediate availability of downloadable, detailed data sheets. Samsung’s announcement is of the imminent shipment of a PCM-based device.

Sometimes it takes decades but NAND Flash semiconductor memory is turning out to be quite the media killer. Over the last decade, NAND Flash memory has killed off 35mm photographic film for all but the most dedicated still-photography enthusiasts. With the advent of dSLR (digital single-lens reflex) cameras that also shoot video, such as the Canon 5D and 7D dSLRs, NAND Flash memory now seriously threatens to replace photographic film for movie and TV production because of the lower costs and faster workflows. The latest confirmation of NAND Flash’s lethal effects is this announcement in the Washington Post reporting that Sony plans to terminate production of floppy disks and will stop selling them in Japan next year after producing them for 30 years. For many who thought the floppy disk dead already, it may come as a surprise that they are still in production but they are apparently still in use in Japan where Sony claims to own more than 70% of the market. NAND Flash simply offers computer users many advantages including more capacity, better performance, and more ruggedness compared to the venerable floppy. Soon, the only remnant of the floppy disk’s former glory may well be the icon on a Microsoft Office application toolbar that serves as a shortcut for saving a document or file.

The proven lethal effects of NAND Flash on other portable media also point to the current controversy between SSD and HDD advocates. Hard disk drives retain their lead over SSDs in storage capacity and storage cost/bit and HDD vendors continue to move heaven and earth to maintain that lead. SSD vendors seem just as eager and determined to overtake HDD vendors and the historic record of NAND-Flash-based storage devices’ ability to kill older, competing media formats is pretty compelling. Already, enterprise-class storage systems are finding compelling applications for SSDs as storage accelerators. Leading-edge PC users including gamers and video producers find SSDs compelling for their speed, albeit at a higher cost for storage. Today, SSDs are mostly used as HDD helpers. Tomorrow may be another story. It obviously won’t happen next year or even the year after that, but I wouldn’t bet against the ultimate outcome.

One of the most ignored Intel announcements of recent memory must be Doug Davis’ early disclosure at IDF (China) on April 14 (see the hour-long keynote video here) of the company’s new Atom-based Tunnel Creek, an SOC specifically designed for embedded applications. Intel’s Atom processor, a relatively low-powered implementation of the “Intel Architecture,” has been taking the low-end notebook and netbook world by storm. Atom processors also work well and have been rapidly adopted in the embedded world when the embedded product’s block-diagram resembles a PC. However, smaller embedded systems can’t adopt the multichip, chipset-style design of PCs. Many smaller embedded systems require even fewer chips for cost-effective implementation.

Enter Intel’s Tunnel Creek, which sports four x1 lanes of PCIe in addition to the Atom processor core; memory, audio, and video controllers; and an LPC block. The simple addition of a flexible PCIe interface means that embedded designers can gluelessly add a variety of different chips to the Tunnel Creek SOC to create embedded designs with minimal BOMs.

Figure 1: Intel Tunnel Creek block diagram

What can you connect to a PCIe interface that would be useful in an embedded design? Here are just a few ideas that immediately come to mind:

1. An ASSP with a PCIe interface. In the same talk where he disclosed Tunnel Creek, Davis also mentioned that Intel will be developing more than one application-specific I/O hub for specific use with Tunnel Creek. In addition, there are many other likely candidates already on the market such as advanced video/graphics controllers from companies such as nVidia and fast Ethernet controllers from companies such as Realtek.
2. An FPGA. Both Xilinx and Altera offer FPGAs with integral PCIe interfaces. Imagine the ability to gluelessly graft an FPGA directly to an Intel Atom-based SOC. Tunnel Creek should be able to do that.
3. An SSD. You can get PCIe-based SSDs that provide more performance than SATA- or SAS-interfaced SSDs because the PCIe interface is more efficient for high-speed I/O than disk-centric interface protocols. Why add an unneeded disk controller to the mix?
4. Your own ASIC. Intel and TSMC announced earlier that the Atom core would be available to select customers as an ASIC/SOC core. Perhaps you don’t have the production volumes needed to qualify as a select customer for that program but you’d still like to avail yourself of Intel’s processor architecture because of the immense pool of existing software, the many available operating systems for the x86 architecture, and the broad development tool support. Tunnel Creek gives you a way of doing so using a standard processor-based SOC that will likely be produced in fairly high volumes. For lower production volumes, a 2-chip embedded design may well be the most economical.

If these possibilities excite your inner design muse, then start bothering Intel to see when you can get your hands on some Tunnel Creek samples.

Network World has just posted an SSD comparison test written by Logan G. Harbaugh. The test pitted some consumer-class SSDs against enterprise-class SSDs and with an Adaptec ASR5805/512 SSD controller and MaxIQ kit, which uses an attached SSD to accelerate attached drives arrays via flash caching. Overall, Harbaugh found that the SSDs improved system performance by a factor of 2 to 10 depending on the product.

The discussed test results illustrate many key points we’re learning about SSDS used both as direct storage devices and as caches for rotating storage. For example, the article discusses the “write cliff,” which is the sudden loss of write performance sustained by some SSDs after they are initially filled. The cause of the performance loss is the need to scavenge free space from deleted files and the need for “wear leveling,” which prevents premature NAND Flash failure in the SSD. If the SSD capacity is not overprovisioned (larger than the rated size), then writes cannot progress until the SSD’s controller finds, liberates, and organizes the free space. If the SSD capacity is overprovisioned, then free-space “garbage collection” and wear leveling can occur as a background task and will not increase the drive’s write latency. The write latency of an SSD that’s not overprovisioned can range unpredictably from milliseconds to seconds depending on the amount of free space to be liberated. Of course, there’s a cost for capacity overprovisioning and the higher cost of enterprise-class SSDs reflects the cost for added storage. The Network World article notes these characteristics in fine detail.

Harbaugh tested the Adaptec SSD controller/Intel SSD combo and drives or drive arrays from Apricorn, Compellent, Dot Hill, Fusionio, HP, and Ritek. The testbed was an HP ML370G5 server running Windows Server 2003 with external storage connected via Fibre Channel through a 2Gbps HP FC switch and the tests were run with IOmeter. Harbaugh notes that the Fusioio 32-Gbyte ioDrive and the HP StorageWorks IO Accelerator for blade servers (made by Fusionio) achieved the highest throughput in the tests. The Fusionio SSD delivered read and write throughputs of 706 and 456 Mbytes/sec respectively while the HP StorageWorks IO Accelerator delivered read and write throughputs on a blade server of 806 and 618 Mbytes/sec respectively. Both products delivered “excellent IOps, with no write cliff.” Note that the Fusionio drive costs $6,829.99 and the list price for HP StorageWorks IO Accelerator ranges from $4400 to 13,200 on the HP Web site for storage capacities ranging from 80 to 320 Gbytes. The tested 160-Gbyte HP accelerator lists for $7700. So performance comes at a price (nothing new there) that’s substantially higher than the SATA drives configured as HDD replacements.

Only the application developer can determine if high throughput and the absence of a write cliff is worth several thousand dollars. In many enterprise-class situations, the additional hardware cost is irrelevant. Online businesses such as Amazon.com have found that even a 1% increase in response time causes lost sales to the tune of millions of dollars because online customers are impatient and they bore easily. They will not wait long before wandering off, perhaps to a faster competitor. Large investment firms measure millisecond increases in online trading latency in terms of millions of dollars as well. The first trading firm to get a deal leaves competitors choking in the dust with no deal at all. So a few thousand dollars to avoid a sudden latency increase measured in tens or hundreds of milliseconds or even seconds is trivial insurance against large potential business losses.

The Network World article notes that one advantage these faster drives have is their use of the PCIe interface rather than the drive industry’s preferred SATA or SAS interfaces. The PCIe interface is closely coupled to the computer’s or server’s processor and can therefore provide very low latency and very high throughput, which is easily increased simply by adding parallel PCIe lanes. Several of the storage products including those from Fusionio and HP that were tested in this article employ PCIe interfaces to improve the storage subsystem’s performance.

Anandtech has just posted a meaty article about SandForce SSD controllers as used in SSDs from OCZ and Corsair. (Understanding SandForce's SF-1200 & SF-1500, Not All Drives are Equal) It’s worth a read from at least two perspectives. First, it gives you some pretty deep insight into the real importance and value of the firmware running on these SSD controllers. As the Anandtech article discusses, controller firmware can make a substantial performance difference using the same hardware. In the case of the SandForce SF-1500 enterprise SSD controller and the company’s SF-1200 “client” SSD controller chips, firmware makes all the difference in performance because the two devices are electrically the same IC. Both chips running their associated firmware are rated at 30K random-read IOPS (I/O operations per second for 4-Kbyte reads) but the SF1500 is rated at 30K random-write IOPS (4-Kbyte writes) while the SF-1200 is rated at 10K random-write IOPS, which is a whopping two-thirds less performance than delivered by the electrically identical SF-1500 controller chip. There’s also an order-of-magnitude difference in rated data reliability between the two controllers, which you’d expect customers to want for enterprise-class SSDs. From the perspective of product positioning, this performance spread makes tremendous sense because the enterprise-class SF-1500 is reported to be substantially more expensive than the SF-1200 and the price premium is largely attributable to the differential speed and data-reliability performance delivered by the controller firmware (along with some extra reliability testing for the SF-1500 chip).

As Anandtech reports, because of a special relationship with SandForce, OCZ apparently got a special “fast” version of the control firmware for the SF-1200 controller that delivers the faster random-write IOPS performance of the SF-1500 and OCZ will reportedly be using that controller-chip/firmware combo in an upcoming Vertex 2 SSD. Anandtech further reports that this “fast” SF-1200 firmware reached at least one other SSD vendor, Corsair, through an early firmware release. Anandtech has tested an early review version of this drive and it delivers the higher performance. A later production version of this controller firmware apparently does throttle the SF-1200’s write IOPS performance to the rated “client”
SSD levels.

Despite Anandtech’s stated concerns, all this versioning and throttling isn’t anything particularly new or insidious in the electronics industry. The end customer pays for performance, which is both a real and perceived value, whether or not the performance is due to hardware or firmware differences. From an SSD customer’s perspective, it’s the drive delivering this performance and most customers will not care or even understand the fine distinction between hardware-delivered and firmware-delivered performance. In fact the Anandtech article notes that Intel does a similar thing by enabling or disabling Hyperthreading on two differently priced Core i5 and Core i7 processors. Same die, different performance. I know of a case all the way back in the 1970s where changing one bit in a product’s firmware image doubled the amount of RAM available to the user. Changing that bit cost the customer a few thousand dollars. So the practice isn’t new. But SSD vendors do need to know the difference. They need to understand the cost/performance tradeoffs they are making, because their products’ performance will reflect the consequences of these choices.

Thus the point of this blog entry is to point out, perhaps even to underscore, that firmware is a big differentiator in SSD performance, just as it is in just about any product category. SSD vendors need to understand this. Companies developing SSD controller chips should be aware that excellent controller firmware can substantially differentiate products, just as it has for SandForce’s SF-1500 and SF-1200 controllers. SSD manufacturers should be ready to grill their controller vendors about the supplied firmware. Is it as good as it can be? Could it be faster? Very good questions to ask as the SSD competitive landscape continues to heat up. SSD controller-chip vendors: be prepared.

Geoff Gasior at The Tech Report has just published a long and very comprehensive side-by-side comparison of four SSDs from Corsair, Kingston, Plextor, and Western Digital. He’s pulled the covers off the drives to look at the guts (and he names names of the on-board controller chips in the process) and Gasior then tests each drive in turn to come up with some really interesting comparisons. If you’re interested in how SSDs are being and will be tested and want to see some surprises in the differentiated results, be sure to read through the entire 10-page article. For the more impatient, here are some key points made in the review:

Controller chips

One of the really interesting elements of the review is a description of each design’s architecture including the controller chip used. Here’s a summary:

Corsair Nova V128 (128 Gbytes)
Controller chip: Indilinx Barefoot ECO
NAND Flash: 16 MLC chips from IM Flash

Kingston SSDNow V+ (128 Gbytes)
Controller Chip: Toshiba T6UG1XBG
NAND Flash: 8 MLC chips from Toshiba

Plextor PX-128M1S (128 Gbytes)
Controller chip: Marvell "Da Vinci" 88SS8014
NAND Flash: 16 MLC chips from Samsung

Western Digital SiliconEdge Blue (256 Gbytes)
Controller chip: JMicron JMF612
NAND Flash: 32 MLC chips from Samsung (double stacked)

The diversity of the controllers and the differing quantities of on-board NAND Flash chips results in a diverse set of I/O performance specs for the drives:

Corsair Nova V128
Rated read speed: 270 Mbytes/sec
Rated write speed: 195 Mbytes/sec

Kingston SSDNow V+
Rated read speed: 230 Mbytes/sec
Rated write speed: 180 Mbytes/sec

Plextor PX-128M1S
Rated read speed: 130 Mbytes/sec
Rated write speed: 70 Mbytes/sec

Western Digital Silicon Edge Blue
Rated read speed: 250 Mbytes/sec
Rated write speed: 170 Mbytes/sec

Take some time to read through the article. Pay particular attention to the well-written discussion of the TRIM command, which is implemented on all of the above drives except for the Plextor drive.

This article is a good example of how people will be evaluating SSDs in the future. Unlike mechanical HDDs, where the read/write performance is largely set by the rotational speed of the spinning platters regardless of the drive vendor or the built-in controller chip manufacturer, SSD performance is very much a function of the NAND Flash parallelism in the drive’s architectural design, the SSD’s controller chip’s design, and the effectiveness of the firmware running on that controller chip. Based on the article’s results, you can see that there’s quite a bit of flexibility in play with respect to SSD performance and that the innovations put into the drive will be sussed out by advanced customers.

PCWorld reports that Micron will soon be rolling out Enterprise-class SSDs based on 34nm, ONFI 2.1, SLC (single-level cell) NAND Flash devices. These drives will employ the 6-Gbit/sec SATA 3.0 interface specification to create an I/O channel with enough bandwidth to support the faster Flash. Doing so makes the soon-to-be-introduced RealSSD P300 SSDs more than competitive with 10,000- and 15,000-rpm Enterprise-class HDDs, which may employ 6-Gbit/sec SATA 3.0 interfaces but cannot fully utilize the improved bandwidth because they simply cannot get the data off the read/write heads fast enough. The inherent scalable parallelism of SSD architectures makes it far easier for SSD designers to bump data bandwidth at will.

Micron will reportedly sell the P300 drives in capacities of 50, 100, and 200 Gbytes. These drives will replace the company’s current RealSSD P200 drives, which deliver sequential read speeds of up to 180 Mbytes/sec and write speeds of up to 115 Mbytes/sec while a fully saturated SATA 3.0 interface theoretically delivers a maximum bandwidth of 750 Mbytes/sec. Practical overhead issues will reduce the maximum effective bandwidth somewhat, but SATA 3.0 can clearly deliver far more throughput than currently achieved by Micron's P200 SSDs. One key to this boost is the faster ONFI 2.1 NAND Flash interface.

In contrast to short-stroked, high-rpm HDDs that require a lot of power and consequently require a lot of cooling, Enterprise-class SSDs draw far less power and require almost no cooling compared to high-rpm HDDs, so there are considerable cost considerations beyond hopelessly simplistic cost/Gbyte metrics when considering SSDs for enterprise-class storage. In addition, SSDs have predictable reliability characteristics that can help data centers avoid catastrophic storage failures in mission-critical applications such as finance and online commerce.