How many computers are in your computer?

Some people seem to get caught up in discussions about weird machines or how big an AI agent must be and whether there will be one, two, 10, or millions; this is not an important issue as it is merely an internal organizational one. What is important are the inputs and outputs: how capable is the system as a whole and what resources does it require? No one cares if Google is implemented using 50 supercomputers, 50,000 mainframes, 5 million servers, or 50 million embedded/mobile processors, or a mix of any of the above exploiting a wide variety of chips from custom tensor processing units to custom on-die silicon (implemented by Intel on Xeon chips for a number of its biggest customers) to FPGAs to GPUs to CPUs to still more exotic hardware like prototype D-Wave quantum computers - as long as it is competitive with other tech corporations and can deliver its services at a reasonable cost. (A supercomputer these days mostly looks like a large number of rack-mounted servers with unusual numbers of GPUs & connected by unusually high-speed InfiniBand connections and is not that different from a datacenter.) Any of these pieces of hardware could support multiple weird machines on many different levels of computation depending on their internal dynamics & connectivity. Similarly, it is foolish to insist on defining whether an AI is one AI or many: any AI system might be implemented as a single giant neural network, or as a sharded NN running asynchronously, or as a heterogeneous set of micro-services, or as a society of mind etc - but it doesn’t especially matter, from a complexity or risk perspective, how exactly it’s organized internally as long as the totality works; the question for AI risk is how dangerous is the totality. The system can be seen on many levels, each equally invalid but useful for different purposes.

Here is an example of the ill-defined nature of the question: on your desk or in your pocket, how many computers do you currently have? How many computers are in your computer? Did you think just one? Let’s take a closer look - it’s computers all the way down.

You might think you have just the one large CPU occupying pride of place on your motherboard, and perhaps the GPU too, but the computational power available goes far beyond just the CPU/GPU, for a variety of reasons: transistors and processor cores are so cheap now that it often makes sense to use a separate core for realtime or higher performance, for security guarantees, to avoid having to burden the main OS with a task, for compatibility with an older architecture or existing software package, because a DSP or core can be programmed faster than a more specialized ASIC can be created, or because it was the quickest possible solution to slap down a small CPU and they couldn’t be bothered to shave some pennies. Further, many of these components can be used as computational elements even if they were not intended to be or hide that functionality. (For example, I believe I’ve read that the Commodore 64’s floppy drive’s CPU running Commodore DOS was used as a source of spare compute power & for defeating copy-protection schemes.)

Thus:

• A common AMD/Intel CPU has billions of transistors, devoted to a large number of tasks:

  • Each of the 2-8 main CPU cores can run independently, shutting on or off as necessary, and has its own private caches L1-L3 (often bigger than desktop computers’ entire RAM a few decades ago⁶, and likely physically bigger than their CPUs were to boot), and must be regarded as individuals.
  • The CPU as a whole is reprogrammable through microcode, such as to work around errors in the chip design, and sport increasingly opaque features like the Intel Management Engine (with a JVM for programmability; Ruan 2014 & SGX), or AMD’s Platform Security Processor (PSP) or Android’s TEEs or Titan chips; these hardware modules typically are full computers in their own right, running independently of the host and able to tamper with it.
  • any floating point unit may be Turing-complete through encoding into floating-point operations in the spirit of FRACTRAN⁷

• the MMU can be programmed into a page-fault weird machine driven by a CPU stub, as previously mentioned

• DSP units, custom silicon: ASICs for video formats like h.264 probably are not Turing-complete (despite their support for complicated deltas and compression techniques which might allow something like Wang tiles), but for example Apple’s A9 mobile system-on-a-chip goes far beyond simply a dual-core ARM CPU and GPU as like Intel/AMD desktop CPUs, it includes the secure enclave (a physically separate dedicated CPU core), but it also includes an image co-processor, a motion/voice-recognition coprocessor (partially to support Siri), and apparently a few other cores. These ASICs are sometimes there to support AI tasks, and presumably specialize in matrix multiplications for neural networks; as recurrent neural networks are Turing-complete… Other companies have rushed to expand their system-on-chips as well, like Motorola or Qualcomm

• motherboard BIOS and/or management chips with network access

  • Mark Ermolov notes that

    It’s amazing how many heterogeneous CPU cores were integrated in Intel Silvermont’s Moorefield SoC (ANN): x86, ARC, LMT, 8051, Audio DSP, each running own firmware and supporting JTAG interface

  These management or debugging chips may be accidentally left enabled on shipping devices, like the Via C3 CPUs’s embedded ARM CPUs

• GPUs have several hundred or thousand simple cores, each of which can run neural networks well (which are highly expressive or Turing-complete), or do general-purpose computation (albeit slower than the CPU)⁸

• the controllers for tape drives, hard drives, flash drives, or SSD drives typically all have ARM processors to run the on-disk firmware for tasks like hiding bad sectors from the operating system; these can be hacked. (Given ARM CPUs are used in most of these embedded applications, it’s no surprise ARM likes to boast that a modern smartphone will contain somewhere between 8 and 14 ARM processors, one of which will be the application processor (running Android or iOS or whatever), while another will be the processor for the baseband stack..)

• network chips do independent processing for DMA. (This sort of independence is why features like Wake-on-LAN for netboot work.)

• smartphones: in addition to all the other units mentioned, there is an independent baseband processor running a proprietary realtime OS for handling radio communications with the cellular towers/GPS/other things, or possibly more than one virtualized using something like L4. Baseband processors have been found with backdoors, in addition to all their vulnerabilities.

• SIM cards for smartphones are much more than simple memory cards recording your subscription information, as they are smart cards which can independently run Java Card applications (apparently NFC chips may also be like this as well), somewhat like the JVM in the IME. Naturally, SIM cards can be hacked too and used for surveillance etc.

• USB or Thunderbolt cables or devices, or motherboard-attached devices: an embedded processor on device is needed for negotiation of data/power protocols at the least for cables/batteries/chargers⁹, and may be even more heavy duty with multiple additional specialized processors themselves like WiFi adapters or keyboards or mice or SD cards. In theory, most of these are separate and are at least prevented from directly subverting the host via DMA by in-between IOMMU units, but the devil is in the details…

• monitor-embedded CPU (part of a tradition going back to smart teletypes)

• random weird chips like the Macbook Touch bar running WatchOS

• …

So a desktop or smartphone can reasonably be expected to have anywhere from 15 to several thousand computers in the sense of a Turing-complete device which can be programmed in a usefully general fashion with little or no code running on the official computer, which is computationally powerful enough to run many programs from throughout computing history and which can be exploited by an adversary for surveillance, exfiltration, or attacks against the rest of the system.

None of this is unusual historically, as even the earliest mainframes tended to be multiple computers, with the main computer doing batch processing while additional smaller computers took care of high-speed I/O operations that would otherwise choke the main computers with interrupts.

In practice, aside from the computer security community (as all these computers are insecure and thus useful hidey-holes for the NSA & VXers), users don’t care that our computers, under the hood, are insanely complex and more accurately seen as a motley menagerie of hundreds of computers awkwardly yoked together (was it the network is the computer or the computer is the network…?); he perceives and uses it as a single computer.