I have not seen a single reference where a whole computer is built inside a chip itself instead of modularizing and spreading it on a board.
I acknowledge that having modular parts enable versatility, but can big silicon companies such as Intel, AMD produce a whole computer with cpu, chipset, RAM, memory controllers, all in a microchip?
I am familiar the concept of SoC but havent seen ALL the components inside single chip.
It is theoretically possible. However I would describe it as practically impossible.
When manufacturing silicon chips, you have a certain defect density over your wafer. Usually chips in the center are fine and at the edges more defects are present. This is usually not a big problem: Lets say you have 1000 single chips on one wafer and 20 defects, caused by process variations, particles on the wafer etc. You will get 20 Chips loss at most, which is 2%.
If you manufactured a single chip on this wafer you would have lost 100%. The bigger the Chip gets the smaller your yield gets.
I work in the semiconductor industry and have yet to see a wafer where all chips are fully functional. Nowadays we have very high yield numbers. But still: There are defects on the wafer.
Another thing is: Not all components in your computer can be manufactured on a silicon chip. For example the coils which are used for the DC/DC regulators cannot be implemented on-chip. Inductors on Chips are quite a pain. They're usually only done for > 1 GHz transformers for signals coupling etc. A power inductor with several nH or even uH is not possible (tm).
Another downside are multiple technologies. CPUs are usually done in a very small CMOS technology for the high transistor integration. However, let's say a headphone output has to drive 32 Ohm headphones. Manufacturing a headphone amplifier in a 7 nm FinFET technology is not ideal. Instead you use different semiconductor technologies with lower frequency but higher current capability. There a a lot of different semiconductor technologies that are used to manufacture all the chips for a single computer.
Regarding memories like DRAMs and nonvolatile memories like Flash: These also need specific technologies. One downside of manufacturing modern Microcontrollers (Processors with RAM and ROM on board) is, that the semiconductor process is somewhat bottlenecked by the internal flash these controllers need. More powerful processors usually don't have onboard program memory (except for a very small mask-ROM which holds the bootloader).
It is still better to combine multiple dedicated chips than trying to put everything on one die. As you've already stated: With modern SoCs there are a lot of formerly separate components now on a single IC.
However, putting everything on one chip is
can big silicon companies such as Intel, AMD produce a whole computer with cpu, chipset, RAM, memory controllers, all in a microchip?
Keep in mind that what you might think of as one silicon wafer may actually be multiple chips in one package. A good example is the latest generation AMD Ryzen 9 CPUs that are made of multiple "chiplets" that are bonded together in one package. AMD does it to improve yield and reduce cost, but the same method could be used to provide flash memory, CPU, and DRAM in the same package.
I have not seen a single reference where a whole computer is built inside a chip itself instead of modularizing and spreading it on a board.
What you are describing is a micro-controller or system-on-a-chip.
Many of the micro-controllers and system-on-a-chip devices out there have non-volatile storage, RAM, CPU, and peripherals in one die. In terms of capability they are comparable to a 1980s or early 1990s era PC.
While not technically one chip, Texas Instruments offers a technology called "Package on Package" for their OMAP mobile phone processors. The PoP chips are BGAs that features solder pads on their top side and balls on the bottom side. Instead of placing several chips next to each-other on a PWB, you stack a CPU, flash memory, and DRAM vertically right on top of each-other.
Another technology that comes close is the Xilinx ZYNQ FPGA. You can get a system running Petalinux with as little as 3 chips + power supplies. Some of the peripherals would also require a physical layer transceiver if they do not fit one of the available IO standards supported by the chip.
In terms of capability they are comparable to a 1980s or early 1990s era PC. that is pretty old information. Modern SoCs are much faster and exceed capabilities of PCs from early 2000's in both computing power and peripherals.
\$\endgroup\$
Commented
Jan 4, 2021 at 7:26
Theoretically, yes. Wafer-scale integration has been discussed in the past.
Practically, no. Manufacturing processes for DRAM and flash are customized and tweaked for those products, so there are extra process steps that are not needed for normal logic. Those process steps drive up the cost of everything on the wafer. Trying to integrate more and more logic on a larger and larger silicon device will lead to a higher number of defects per device, which will increase the need for redundancy and self-repair.
Finding a package to reliably support, connect, and dissipate heat from a very large piece of thin, brittle silicon is another problem.
It just doesn't make sense. If it did, Intel and ARM and AMD would be doing it.
In addition to all the other answers: We are kind of getting there, where it makes sense.
Early computers had dedicated chips for cache, graphics, audio, bus controller (PCI, AGP etc.), memory controller, network, serial/parallel ports etc. etc.
Today most of that is integrated in the CPU.
Look at a modern AMD Ryzen mainboard, for example this Asrock Deskmini A300:
It pretty much only provides the connectors, slots for RAM, storage and lots of decoupling capacitors. The few chips you see are just there for I/O stuff (e.g. Realtek audio codec, ethernet PHY, ESD protection, level shifters etc.), BIOS, fan control and power regulation.
Sure, it’s possible. There’s several issues however:
Silicon defects increase with area. The larger the chip, the more likely the die will have defects in it. Some of these can be worked around (such as mapping redundant memory cells) but in general the yield becomes unmanageably bad above a certain die size. Closely related to this is testability, which again becomes very challenging and time-consuming for large die.
Different parts of the system will require different types of process to best serve the function. A CPU will want to use a low voltage and low-threshold cells for speed, while a peripheral connection may need higher voltage for compatibility or to run mixed-signal blocks. These often work against each other, forcing trade offs in speed or cost.
I/O connections need to be brought out to be useful. This implies some kind of larger PCB to hold them. Power must also be brought to the die and distributed, which becomes increasingly difficult with larger die.
Finally, large memories (DRAM, flash) consume a lot of area, and need special process (such as trench capacitors for DRAM.) It’s more economical to build them on processes optimized for them than to wedge them onto the same die as the CPU.
This all said, in recent years large CPUs have moved away from being large single die, and instead are composed of ‘chiplets’ arranged together with other subsystems on a multchip package. The AMD EPYC is a great example of this approach, using a scalable group of compute units interconnected to each other by a high-performance datapath fabric. More about that here: https://www.nextplatform.com/2019/08/15/a-deep-dive-into-amds-rome-epyc-architecture/
I think the existing answers explain quite well why you still need a motherboard, even for SoCs that integrate as much as possible into the chip. Fundamentally you are constrained by the need to interface power and I/O to your computer.
With that said, it's certainly possible to find applications that minimize the amount of additional hardware required to put the silicon to work. The only place I can think of where a functional computer can be found in its final, working, application in the form of a single piece of silicon is an RFID tag.
This particular example uses the Impinj Monza R6 chip, whose manual gives a block diagram of its design :
The chip contains power management circuitry to collect RF energy from the antenna to power the chip, a microcontroller with ROM and writeable user memory, password protection, etc.
The final product requires no motherboard and the only power and I/O comes from the single wire loop used as an antenna. The wire antenna bonds directly to the IC on its only two contact pads :
You might consider the plastic sticker backing to be a "motherboard" of sorts, I suppose, but it otherwise requires no additional components to function.
Fundamentally, this is somewhat a question of semantics and where you want to draw the line between the computer, the box you put the computer into, and the perhipherals that you attach to the computer.
The fabrication process used for a high-end CPU will be designed primarily for cache memory (SRAM) because modern CPU's are mostly cache, by area. The logic is only a small part of it.
The fabrication for SDRAM (usually just called "RAM") is totally different from SRAM, and very specialized. SDRAM fabs don't produce anything else.
This, alone, is enough reason to have different fabs for SDRAM and CPU's.
There is also a modularity issue. Some people want multiple disk controllers, some want only one, etc. So committing all those decisions to a silicon wafer would probably not be the best idea. There are hundreds of different motherboards out there all doing slightly different things. The resources required to design and test a motherboard are small compared to the resources required to design and test a CPU.
All of that said, there are nonetheless so-called system on chip (SOC) processors out there in the micro-controller realm. They have voltage regulators, flash memory, SRAM multiple peripherals all on one chip. So it IS possible. It just doesn't seem to fit the market needs to do the same thing with high-powered processors.
Any wafer fabrication process calls for a (usually large) number of different steps, and these will be somewhat different for RAM, logic and specialised high-speed functions such as video and USB. Those functions could be manufactured on the same wafer with moderate compromises, as is done for microcontrollers, but power management functions such as high power DC-DC converters require significantly different fabrication and would be impractical. By analogy, you can make most parts of a motor car from sheet metal but you’d struggle to make an engine that way, not that it would be technically impossible but certainly not practical. Besides, much of the function of a motherboard is to house the connectors, so any monolithic solution would need something analogous to a motherboard even if it only had one chip on it.
@user4574 and @hacktastical have covered the major points, but there are a few others worth mentioning:
Suppose you are able to put all of the electronics on one chip. Congratulations, you are locked into a particular configuration of RAM, ROM, and peripherals. Any changes to these requires a completely different chip, which costs money every time you do that.
This issue isn't so bad in the microcontroller market, because there will always be plenty of embedded applications that only need 8k of RAM and 32k of ROM. These chips only need to be designed once, and sell tens of billions of units every year, forever.
Demand is much different in the PC/laptop/phone market. There is an expectation of more RAM and different peripherals every 2-3 years. So you are constantly designing new chips, to fit all of the various niches of the market and which last on the market for only a few years before being considered obsolete. You will be lucky if any given design sells one million units before becoming obsolete.
Meanwhile, your competitor produces one general-purpose CPU design every 10 years which can be re-used in various memory and peripheral combinations. Your competitor has less frequent development costs, produces a smaller product line, and sells 1000x as many units as you (because of their chip's versatility). Who do you suppose is going to have a cheaper product?
CPUs need an oscillator. Some microcontrollers have an on-chip RC oscillator, which produce at best 20 MHz. However, that's way too slow for the PC (2000+ MHz), laptop (500+ MHz), and cell phone (200+ MHz) markets. (These numbers are for the lowest end units; most units have clock rates much higher.) At these speeds, you need a real crystal for these, and it's way too expensive to put them on the same die as the CPU. So the crystal is put separately on the motherboard.
Digital circuits need bypass (decoupling) capacitors. Instead of taking up valuable chip space, it is cheaper to put them externally on the motherboard.
Often the power supply needs to be brought down to a lower voltage (e.g. 5V to 3.3V). The voltage regulators which do that dissipate a lot of heat. Better to have that on another chip on the motherboard, to keep that heat away from your CPU.
As far as I know only one company produces a wafer scale product for AI neural network applications, which is Cerebras
It contains over a trillion transistors and it's cost last time I checked was around $200k
Depends what you mean by computer and “all components”. An Arduino chip has input, output, storage, memory, and central processor with ALU all on one chip (other SOCs have far more, including network and graphics units). Even the old Intel (major vendor) 8051 is a fairly complete system, and SOC variants are used as single chip computer solutions in perhaps billions of products.
But even an Arduino doesn’t include AC power supply, LEDs, and physical buttons on chip.
Maybe I'm missing something, but I'm looking at this Arduino with an Atmel ATmega328 chip and the only external (computer specific) part I see is the crystal. One advantage to putting the whole computer in one chip is that routing larger busses to connect all the parts becomes a problem on printed wiring boards as buss size increases and is more easily handled inside a chip. A trade off is accessibility of each functional component, which we largely solve with JTAG or something similar.
It's called "SoC" and they're widely used in mobile devices. Beyond the main chip you just have a bunch of capacitors and resistors and things like charging chips to deal with electrical environment.
https://en.m.wikipedia.org/wiki/Texas_Instruments_TMS1000
This TMS1000 is the first computer on a chip and one of the first CPUs. It is from 1979.
< It combined a 4-bit central processor unit, read-only memory (ROM), read/write memory (RAM), and input/output (I/O) lines as a complete "computer on a chip". It was intended for embedded systems in automobiles, appliances, games, and measurement instruments
Yes, there's a technique that shows promise: it's called Silicon Interconnect Fabric.
Read all about it here:
https://spectrum.ieee.org/goodbye-motherboard-hello-siliconinterconnect-fabric#toggle-gdpr
