More than a decade of MIPS multi-threading
Last year we celebrated the 30th anniversary of the MIPS CPU architecture, recognising its strong legacy since its introduction in 1986. In this post, however, we are celebrating the fact that it’s now over a decade since the introduction of one of the specific features inside MIPS – something that sets it apart from the competition – hardware multi-threading.
Multi-threading was first introduced into the MIPS architecture in 2005 and it is an important part of what makes MIPS a compelling offering in the market for licensable CPU IP. Since its introduction with the 34K, it has been a mainstay of many MIPS CPUs, such as the 1004K, interAptiv, and the more recent Warrior cores such as the I6400 and I6500. In that time, at least 700 million SoCs have shipped based on processor cores utilising MIPS multi-threading technology.
What is multi-threading and why is it important anyway?
To answer that very question, Imagination recently published a white paper that gives a high-level overview of MIPS multi-threading, and for anyone wanting to get a clear understanding of the subject, we recommend reading it.
Essentially, multi-threading is designed to maximise the efficiency of how a CPU core is used. In any real-world system, a CPU will not be fully occupied all the time due to events such as data and instruction cache misses or a functional block being occupied with another task. Any of these can cause work on the current thread to stall. In these situations, it makes sense to start working on something else while it is waiting. It’s similar to how in a modern hypercar, such as the McClaren P1 the electric engine is used to ‘fill-in’ gaps in the power curve caused by turbo-lag, providing on-going performance, all of the time.
A small amount of additional hardware is required to enable hardware multi-threading capabilities in a CPU, but similarly to multi-core as a parallel execution environment, the actual performance benefit from multi-threading can vary, depending on the application and software tasks being run. On some software workloads, performance can improve well over 2x with multiple threads. As such, multi-threading is typically more efficient than multi-core in terms of silicon area and overall power consumption – both of which are critical in embedded systems.
Multi-threading also has a key advantage in that in unlocks the full potential of virtualization. The zero latency context switching that multi-threading delivers provides a huge performance boost for virtualization, as discussed at length in this webinar, where we note how this could bring significant benefit to SoC vendors, OEMs and operators. This same benefit can also be leveraged for low-latency interrupt response in deterministic, real-time embedded systems.
So who has shipped multi-threaded MIPS processors?
As you would expect, a wide range of companies have shipped multi-threaded MIPS processors over the years for numerous applications.
MIPS multi-threaded CPUs are particularly well suited to networking and communications processing. This is thanks to near instant context switching, which makes them very efficient at handling things such as virtual machines in real-time. It’s no surprise then that networking is a very significant area for MIPS CPUs. In fact, you probably didn’t know that 25% of all SoCs manufactured for networking products in the last four years used a multi-threaded MIPS processor.
In this post from 2014, we go into detail about a number of MIPS-based networking processers from a number of manufacturers. Here are a few examples:
- Ikanos Fusiv® Vx575 – a family of multi-mode gateway processors for smart residential gateways from Ikanos, now part of Qualcomm.
Ikanos Fusiv Vx575 processors feature a dual-core, multi-threaded MIPS interAptiv CPU
- Altair FourGee-3802 – This LTE-Advanced baseband processor from Altair (now owned by Sony) conforming to 3GPPP release 10. The FourGee-3100 MIPS-based chipset was also used for several Chromebook laptops, such as the HP Chromebook 11 and the ASUS Chromebook 13.3. Ralink Technology – Acquired by MediaTek in 2011, Ralink was famed for its Wi-Fi chipsets and used both 34K and 1004K multi-threaded products. The RT6856, based on a MIPS 34K multi-threaded CPU, could be found in many popular brands of home wireless routers such as Asus, D-Link, Linksys and ZyXEL. Equally many Ralink chipsets such as the TC3162(U) were used in xDSL router/modems from Asus, D-Link, Huawei, and TP-Link, among others.
- Lantiq VRX220 and MELT integrated device controller – Now owned by Intel, Lantiq is a long-time customer for multi-threaded MIPS CPUs. In 2014 its CEO Dan Artusi spoke at the annual Imagination Tech Summit (2017’s event is currently taking place in the US) and more multi-threaded products are on the way. Lantiq has also more recently announced its carrier-class GRX350 processor, based on MIPS interAptiv CPUs.
- A very common location for 34K MIPS CPUs over the last few years are in the SoCs from MStar found in digital televisions from the likes of Panasonic and LG. It’s a very large market – in 2015 32% of all TVs shipped globally featured a MIPS multi-threaded processor.
- MIPS can be found in the enterprise storage arena courtesy of PMC-Sierra, who made use of the multi-threading feature to offer highly competitive performance for its maxRAID architecture in the enterprise server space. PMC noted, “MIPS multi-threading capability… enables us to develop the higher performance, lower power solutions our customers require.”
- Valens produces the HDBaseT standard, a technology used for digital media distribution, and employs MIPS multi-threaded CPUs. HDBaseT delivers high-bandwidth digital communication over Ethernet, negating the need for more expensive HDMI. It’s popular in connected home and Valens last year announced its plans to work with car manufacturer Daimler to bring it into the automotive space.
- In the automotive space, MIPS has a significant presence thanks to Mobileye, a world leader in ADAS (Advanced Driver Assistance Systems); Mobileye’s technology is found in the vast majority of these systems today. It has been using MIPS multi-threaded CPUs including the 34K, interAptiv and the 1004K since the announcement of the EyeQ2 in 2006. Mobileye has maintained its use of MIPS, recently announcing it will be using the I6500 CPU in its upcoming EyeQ5, scheduled to hit the market in 2018. Mobileye noted that: “Imagination’s multi-threaded MIPS CPUs have helped us achieve performance increases of more than 6x with each successive generation of EyeQ® SoCs. Now with the EyeQ5® we are looking at an 8x increase.”
- Denso, one of Japan’s best-known automotive components manufacturing companies, is currently partnering with Imagination on research around the potential of using multi-threading technology in ADAS. DENSO is looking to make use of how MIPS’ multi-threading capabilities can boost performance in embedded applications that require superior compute capabilities within ultra-low power envelopes.
- A multi-threaded MIPS interAptiv CPU running at 550MHz is used in the Creator Ci40 IoT hub developer board. This helps to give it a serious performance advantage over other more hobby-focussed boards and means the Creator Ci40 can act as the focus point for serious, scalable IoT projects. This post discusses a white paper that has benchmarks that expose the benefits of multi-threading on the Ci40 for IoT.
As this quick run-through demonstrates, MIPS multi-threading CPUs have been found in a huge number of products across many different categories over more than a decade – and that continues to be the case.
As we move from LTE to next-generation technologies support for simultaneous multi-threading technology in MIPS I6400 and I6500 cores makes them ideal for many next generation applications including 5G’s high speed enhanced mobile broadband. As we explain in this post on 5G, carrier aggregation, a feature that is vital to increasing bandwidth to reach 5G’s capacity requirements, is a perfect candidate for MIPS multi-threading, as each thread can be used to maintain the context of a component carrier.
In addition, companies are also using MIPS multi-threaded CPUs for the LTE modems in many mobile devices.
Thanks to its unique multi-threaded capability, particularly in areas such as networking and automotive, MIPS CPUs continue to offer a highly attractive combination of performance, power-efficiency and broad eco-system support to the electronics industry.
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