Hacker News Reader

Hacker News

Comment by ianhowson | Hacker News Reader

Full thread

ianhowson

There are probably another order of magnitude more computers in a 'computer' than Gwern estimates.

Consider:

- Power management chips (of which there are dozens) each containing programmable MCUs

- Batteries, of course, contain one or more MCUs each

- Clocks

- 'Glue' MCUs for things like DMA controllers and USB controllers. (USB controller firmware has been exploited from the port side, and it's not upgradeable)

- Supervisors

- RGB LEDs (!)

- SD cards have several (see Bunnie's work)

- Ethernet, WiFi and Bluetooth controllers contain several small and usually a few large computers each

Some of these have fully-baked ROM code, some are programmed and modifiable through flash, and some have firmware written at driver load time to save money.

View on HN

Many of those chips are not programmable though, or are 'programmed' through things like voltage dividers.

At what point do you consider a chip a 'computer'? Would something like a voltage regulator or mux/demux count as an ASIC?

I'm considering anything that runs firmware. I wouldn't consider e.g. a regulator with configurable voltage via resistor divider to count.

I would consider a switchmode PSU where the main switch FET is driven by a microcontroller running firmware (they can then have an I2C/SPI input to allow programmable voltage control). There are probably dozens of these in any modern computer.

I once knew a hardware engineer who worked on a team designing cutting-edge equipment. His mantra was “just use a PIC chip”. He had all sorts of war stories about other engineers coming to him with power regulator designs they just couldn’t get right. He’d often add a PIC chip or two and have the firmware dev write a few routines in C. Problem solved.

PIC chips are small, they are everywhere, they are very useful for adding complex, software-defined behavior (including DSP) at the circuit component level, and they are full general-purpose CPUs with onboard RAM and programmable ROM.

Sprinkling a ton of micros around a board can create a small nightmare for the software developers though, just working out what version of the firmware is running on each chip on the board can become a painful task. (if the software is 'simple enough', this may not be a problem, but it does tend to grow...)

Often you're unaware that these things contain firmware. They're just sold as e.g. 'bluetooth controller', but internally, there's a largish processor, a chunk of RAM and firmware in ROM mask. The firmware versioning is implicit in the chip revision.

(Of course, this just moves the problem around; it's not uncommon for a chip revision to break software elsewhere in the system.)

At what point do you consider a chip a 'computer'?

I would say anything that approaches a Turing-complete machine.

Many of those /are/ programmable. Here's the code we used to get code execution on an SD card bought at the markets in Shenzhen (the project I did with bunnie, referenced above): https://github.com/xobs/ax2xx-code

The factory needs to get code on there somehow, and usually the method isn't documented. Oftentimes it's not locked down.

The blog entry "On Hacking MicroSD Cards" (2013):

https://www.bunniestudios.com/blog/?p=3554

> At what point do you consider a chip a 'computer'?

IANACS, but I'd say the point at which it becomes capable of running Turing-complete languages. This probably covers anything that has a firmware, save maybe if there exist firmwares programmed in limited languages that can't execute arbitrary computation.

Reply on news.ycombinator.com