Historically, in the world of mobile devices, the NAND Flash storage subsystem has always been on a level of its own. This is driven by the requirement for a small single BGA package form factor and the demand for very low power consumption.
Another reason is the extremely tight level of integration in mobile systems. This requires extensive interoperability and qualification sessions involving the host platform with each NAND Flash storage device.
The constant push for faster, better performing systems blurs the lines between the performance demands of mobile devices and consumer PCs. This is driving the need to start exploring other solutions that could enable the next leap forward in mobile device technology.
Before we dive into this article, it’s worth learning a few details about the evolution of mobile NAND flash memory storage in our previous article. Click on the banner below.
Read: The evolution of mobile NAND flash memory storage
Why put PCIe NVMe BGA SSDs on a phone?
The PCIe bus is very versatile and today is the primary form of interconnect between processor and expansion cards, networking, storage, and peripherals in almost all classes of devices, including mobiles. .
In mobile applications, PCIe is generally used to connect the CPU with radio modules (WIFI, Bluetooth, cellular modem, etc.). Expanding its use to include storage devices is a logical choice since the PCIe hardware interface is already part of the processor development, testing, and qualification program. In addition, replicating, validating, and testing identical circuits (by adding multiple PCIe links) is much more cost effective than investing in totally unique design elements (like the circuits needed for UFS).
Recent advancements in silicon process nodes and NAND Flash controller architecture add to the mobile BGA SSD drive. The BGA SSD can now compete in power / performance (Watts / GBps) with UFS. As we dig even deeper, it becomes evident that we have to ask ourselves why mobile devices don’t use NVMe BGA SSD.
Rate of evolution
Let’s take a look at the release schedule and data rate supported by PCIe and UFS over several years of coexistence. PCIe specifications allowed comparable data throughput at least 2 generations before UFS. Our next-gen phones could be up to 3.5 times faster with the BGA NVMe SSD.
Aggressive approach or product maturity?
When a new UFS specification is released, the entire mobile industry rushes to develop, produce and qualify their products to catch the next generation of flagship mobile devices. It usually takes less than a year for the first supplier to start issuing samples of their products.
Considering an equally aggressive approach to PCIe would result in an immediate and extreme increase in performance in the same amount of time. It might even allow lane reduction (1 lane), which helps improve motherboard routing and takes up less PCB area, which is essential in such small and dense systems. If this change had happened in 2019, we could have had a PCIe Gen5 NVMe BGA SSD with 1 or 2 lanes (3.5 or 7 Gb / s) in direct competition with UFS 3.1 (limited to 2 Gb / s) by 2021.
While less exciting, but just as important, a BGA SSD improves time to market as phones benefit from components that have been tested, mass-produced, and adopted across a wide range of platforms. For example, the PCIe Gen3 x2-lanes (1.6 Gb / s) specification was released 6 years earlier than UFS 2.1 (1 Gb / s) and Gen4 x2-lanes (3.5 Gb / s) was released. 1 year earlier than UFS 3.0 (2 Gb / s). s).
Scale of development and production
A NAND Flash controller integrated circuit contains many different functional blocks which are commonly referred to as IP blocks (intellectual property blocks) or simply IP.
Two flash controllers that share the same interface, but are designed for different performance levels, can share IP addresses, including host interface high speed analog circuitry (PCIe, UFS) and NAND Flash I / O.
A BGA SSD benefits the entire PC and Enterprise ecosystem. For example, an entry-level DRAM-free NVMe M.2 PC SSD could simply be repackaged as a BGA SSD. The two SSDs would share the same Flash controller, most of their firmware, and several other development and testing resources. This allows the NVMe BGA SSD to benefit from economy of scale, resulting in better costs for both product lines and a much faster time to market.
Barrier to entry
Due to the high level of integration in mobile devices, there is absolutely no room for compatibility issues. Both host processor and peripheral manufacturers invest considerable effort to ensure that all parts listed on the AVL (Approved Supplier List) have been thoroughly tested and qualified together.
This means that once the industry has settled on the interfaces to interconnect the components, there must be strong compelling reasons for the changes. Although PCIe is not the officially adopted standard for mobile storage subsystems, it is already used to connect other subsystems. This greatly simplifies the migration from storage to PCIe.
Pioneers and expectations
In our previous article, we mentioned that BlackShark (member of the XiaoMi group) was the first to integrate an NVM BGA SSD into a flagship phone. The current processor of the phone cannot boot from NVMe, so the Phison NVMe BGA SSD (Phison E13T BGA SSD) was paired with a UFS 3.1 device in a RAID 0 configuration. This allowed the storage subsystem to ” achieve nearly 3 GB / s of bandwidth.
While working with BlackShark, Phison was able to test a wide range of other Phison NVMe SSDs to demonstrate the potential for design reuse and even greater bandwidth. Phison plans to launch a Gen4x2 BGA SSD in the first half of 2022.
Phison is committed to supporting BGA SSD on mobile phone applications and we are excited about the possibilities the future holds.
