First N1 Silicon: Enabling the Ecosystem with SDPs

A little known fact about Arm is that the company designs its own silicon test platform – actually deploying them on development board to enable validation and software development on hardware that Arm and developers have full control of. The latest generation was the Juno platform, which in its first revision started off with a Cortex A57 and served as the fundamental silicon testbed for ARMv8 software.

Ever since Arm started the programme in 2014, Arm has shipped over 1400 boards both internally and to its partners. The amount of chips we’re talking about here sounds paltry, however we have to keep in mind we’re talking about very limited shuttle runs on MPW (multi-project wafers) where Arm shares wafer space with numerous other companies.

For today’s announcement, Arm had the pleasure to reveal that it received back the first working Neoverse N1 silicon back in December – with the chips meant to be integrated into the new Neoverse System Development Platform (SDP).

The N1 SDP represents major step for Arm as it not only is the first silicon to come back with the N1 CPU, but also is Arm’s first own 7nm silicon. The platform represents a major proof of concept of the IP, as well as interoperability with third-party IP, employing a lot of the peripheral IP such as PCIe and DDR PHY supplied by Cadence.

The actual hardware is a limited implementation of an N1 SoC – we find a 4-core N1 CPU with 1MB L2 configuration in the form of 2xMP2 connected to a CMN-600 with an 8MB SLC setup.

The board includes a CCIX compatible PCIe 4.0 x16 slot which serves the crucial role of enabling development and demonstrating cache-coherent integration with CCIX hardware such as Xilinx’s FPGA.

The N1 SoC actually doesn’t contain dedicated I/O IP, rather Arm implements all connectivity via a dedicated FPGA which serves as the I/O hub, supporting various connectivity options such as Ethernet, USB, SATA and so on.

Naturally the big selling point of the SDP is its completely open-source firmware stack from not only the OS drivers, but more importantly the SCP and MCP firmware.

An important new feature that is first employed by the new N1 CPU is the introduction of statistical profiling extensions (SPE). The new extension enables the first ever self-hosted profiling capability in an Arm CPU – meaning we don’t require a separate CPU or system having to read out microarchitectural counters. Instead the new SPE can be configured to directly write this information into memory. The tool is extremely useful for tracing code and analysing core behaviour, identifying possible performance issues and further squeezing out the maximum performance out of a platform, something Arm is taking very seriously if it wants to succeed and gain adoption in HPC.

Finally, the N1 SDP will be available later this quarter – although don’t expect the board to be easily attainable for the average user.

E1 Implementation & Performance Targets End Remarks: Strengthening the Infrastructure Ecosystem
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  • WinterCharm - Wednesday, February 20, 2019 - link

    There's a gigantic Arm vs x86/64 battle brewing for the entire computer industry. ARM is just more efficient at every level, and if software is properly optimized it performs brilliantly.
  • eva02langley - Wednesday, February 20, 2019 - link

    However, it doesn't have the raw power required for many fields like scientific, compute and research. The core-count is also a huge factor in the upcoming future and unless you develop a chiplet approach, ARM is going to face the same issue of monolithic chips.

    The next chiplet evolution will require stacking. The future is way more related to modularity than the chip architecture. Don't get me wrong, the more advancement, the better for everyone, but I don't believe ARM is going to render x86 obsolete, hovwever I believe multi-chips SoC are going to render monolithic chip obsolete in the computer world.
  • SarahKerrigan - Wednesday, February 20, 2019 - link

    Sure it does. There are ARM supercomputers, and this very article shows an N1 core outperforming Zen on single-thread, and both Zen and SKL-SP on throughput.
  • HStewart - Wednesday, February 20, 2019 - link

    I think you are forgetting the very nature of RISC (Arm) vs CISC (x86) architectures. By the nature of designed of RISC - reduce instruction set, it takes more instruction to execute same operation than CISC. For simple stuff RISC can likely do better but remember also modern x86 based CPU also break down more complex instructions in simpler instruction so it can run one multiple pipelines.
  • SarahKerrigan - Wednesday, February 20, 2019 - link

    Dude, I work in the semi industry, and I've designed pipelined cores. Saying "ARM's workload-demonstrated higher performance doesn't matter because x86 is CISC" is idiotic.

    SPEC isn't "simple stuff." It is a selection of extremely compute-intensive workstation loads, one that the whole industry - including Intel - uses to demonstrate comparative performance.
  • HStewart - Wednesday, February 20, 2019 - link

    The biggest thing I found that seems misinformation is statement that these are estimates and this chip is simulated which tells me they don't need the real numbers.

    All I am saying is that CISC instructions can do more than RISC instructions per instruction, and it depends on compiler to take advantage of the those instructions. Please note I never sated it does not matter and that was in your words. I just mention considerations need to take in account of different architextures and the fact they are comparing future simulated designed to last year designs.
  • Andrei Frumusanu - Wednesday, February 20, 2019 - link

    > All I am saying is that CISC instructions can do more than RISC instructions per instruction

    Nobody cares. If the performance per clock is same or higher, you're just arguing about semantics.

    Internally CISC processors break things down into RISC like µOps anyway.
  • ZolaIII - Wednesday, February 20, 2019 - link

    @Andrei Frumusanu what would be estimated size of an A55 core with similar amount of cache as on represented E1 on 7nm lithography? I am very curious about that one. Also comparation to the A72 & A73 should be a good thing as ARM clames it reaches their level of performance. Its very interesting first born (SMT) and much needed one.
  • zmatt - Wednesday, February 20, 2019 - link

    When people talk about complex instructions they don't mean something like find the derivative of x^2. They mean something like a conditional move operation. The speed advantages on paper between RISC and CISC are in theory a wash. This is because while CISC can conceivably do more in an instruction, RISC can do more instructions per clock generally. In the real world the simplicity of RISC means usually, all other things being equal, the chips are simpler and can run higher clocks, draw less power and generate less heat for a given level of performance.

    x86 chips haven't actually been CISC since the mid 90's. Both Intel and AMD have been making chips that take the CISC instructions and run them through an instruction decoder that then hands RISC instructions to the actual cpu. Yes this does incur some overhead but it frees up cpu design quite a bit without being so closely tied to backwards compatibility.

    The fact that modern x86 chips ultimately are actually executing code as reduced instruction sets shows you don't understand the concept.
  • Wilco1 - Wednesday, February 20, 2019 - link

    x86 is still a CISC ISA irrespectively of how it executes instructions. Note that compilers predominantly use the simpler instructions, rather than the microcoded instructions and that's why it's possible for x86 to be fast at all.

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