Booting from a vinyl record
So this nutty little experiment connects a PC, or an IBM PC to be exact, directly onto a record player through an amplifier. There is a small ROM boot loader that operates the built-in “cassette interface” of the PC (that was hardly ever used), invoked by the BIOS if all the other boot options fail, i.e. floppy disk and the hard drive. The turntable spins an analog recording of a small bootable read-only RAM drive, which is 64K in size. This contains a FreeDOS kernel, modified by me to cram it into the memory constraint, a micro variant of COMMAND.COM and a patched version of INTERLNK, that allows file transfer through a printer cable, modified to be runnable on FreeDOS. The bootloader reads the disk image from the audio recording through the cassette modem, loads it to memory and boots the system on it. Simple huh?
Inside the 8086 processor, tiny charge pumps create a negative voltage
You might wonder how a charge pump can turn a positive voltage into a negative voltage. The trick is a “flying” capacitor, as shown below. On the left, the capacitor is charged to 5 volts. Now, disconnect the capacitor and connect the positive side to ground. The capacitor still has its 5-volt charge, so now the low side must be at -5 volts. By rapidly switching the capacitor between the two states, the charge pump produces a negative voltage.
Rainbow – an attempt to display colour on a B&W monitor
The aim of this project was to display a colour image on a black and white monitor, by overlaying an acetate bayer filter over the monitor and mosaicing a colour image.
Die shrink: How Intel scaled down the 8086 processor
The revolutionary Intel 8086 microprocessor was introduced 42 years ago this month so I’ve been studying its die. I came across two 8086 dies with different sizes, which reveal details of how a die shrink works. The concept of a die shrink is that as technology improved, a manufacturer could shrink the silicon die, reducing costs and improving performance. But there’s more to it than simply scaling down the whole die. Although the internal circuitry can be directly scaled down, external-facing features can’t shrink as easily. For instance, the bonding pads need a minimum size so wires can be attached, and the power-distribution traces must be large enough for the current. The result is that Intel scaled the interior of the 8086 without change, but the circuitry and pads around the edge of the chip were redesigned.
Classic ThinkPad Thermal Paste Change
Those who know me know that I am a bit fan of the oldschool Lenovo ThinkPad laptops with real 7-row keyboards. I own several *20 models from 2011 including W520, T420s and X220 ones. They still rock when it comes to ‘laptop computing’ and they are dirt cheap on any auction platform. They only got one flaw … that thermal compound on CPU (and sometimes GPU) gets older a lot faster then these laptops.
Reverse-engineering and comparing two Game Boy audio amplifier chips
The Nintendo Game Boy contains an audio amplifier chip for sound through a speaker or headphones. In this post, I reverse-engineer this chip and compare it with the later Game Boy Color chip (reverse-engineered earlier). Unexpectedly the Game Boy Color uses an entirely different amplifier design from the original Game Boy, which may explain why the two systems sound different.
Perhaps the highly anticipated moment that I’m going to contextualize today is totally inevitable, in a way. For years, there’s been a rumbling that Apple would take its knowledge of the ARM processor architecture and bring it to its desktop and laptop computers. Next week, at a virtual Worldwide Developers Conference, the iPhone giant is expected to do just that. Of course, many will focus on the failed partner, the jilted lover of the business relationship that led to Apple’s move to vertically integrate: Intel. But I’m interested in the demise of the platform Intel vanquished on its way to taking over Apple—and the parallels that have emerged between PowerPC and Intel over time. Today’s Tedium dives into Apple’s long list of jilted processor partners, leaning closely on the shift from PowerPC to Intel. Keep Apple happy, or else.
Greetings and salutations internet person! Have you ever pissed off a customer so much they bought a domain and stood up a website to shit on your asinine and boneheaded business practices? GE just did.
I just wanted a tall, cold, refreshing glass of water at 3am only to be greeted by a fucking atomic countdown on my trusty cold water and ice dispensing pal.
Pictures from inside the German intelligence agency BND
The German foreign intelligence service Bundesnachrichtendienst (BND) is moving to a brand new headquarters in Berlin. Here we show some unique pictures from inside the former headquarters in the village of Pullach and also give an impression of what the new building looks like.
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ZFS versus RAID: Eight Ironwolf disks, two filesystems, one winner
We exhaustively tested ZFS and RAID performance on our Storage Hot Rod server.
Extracting ROM constants from the 8087 math coprocessor's die
I opened up an 8087 chip and took photos with a microscope. The photo below shows the chip’s tiny silicon die. Around the edges of the chip, tiny bond wires connect the chip to the 40 external pins. The labels show the main functional blocks, based on my reverse engineering. By examining the chip closely, various constants can be read out of the chip’s ROM, numbers such as pi that the chip uses in its calculations.
A Codebreaker's Dream: The Bombe!
What is this, sporting dozens of colorful knobs, almost like a “turn-the-knob” toddler’s game at a playground in a nearest mall? This the awesome British Bombe electro-mechanical codebreaking machine which only had one purpose: to determine the rotor settings on the German cipher machine “ENIGMA” during WW2.
OpenBSD on the Microsoft Surface Go 2
I used OpenBSD on the original Surface Go back in 2018 and many things worked with the big exception of the internal Atheros WiFi. This meant I had to keep it tethered to a USB-C dock for Ethernet or use a small USB-A WiFi dongle plugged into a less-than-small USB-A-to-USB-C adapter. Microsoft has switched to Intel WiFi chips on their recent Surface devices, making the Surface Go 2 slightly more compatible with OpenBSD.
DVD+R and DVD-R; What was that about?
A format war within a format...
GPU architecture resources
I am often get asked in DMs about how GPUs work. There is a lot of information on GPU architectures online, one can start with these:
Tiny transformer inside: Decapping an isolated power transfer chip
I saw an ad for a tiny chip that provides 5 volts of isolated power: You feed 5 volts in one side, and get 5 volts out the other side. What makes this remarkable is that the two sides can have up to 5000 volts between them. This chip contains a DC-DC converter and a tiny isolation transformer so there’s no direct electrical connection from one side to the other. I was amazed that they could fit all this into a package smaller than your fingernail, so I decided to take a look inside.
Hacking together a USB-C charger for a cheap Chromebook
Only one thing won’t charge with USB-C, my awfully cheap ($190 for 4GB of RAM) Samsung Chromebook 3, a machine I use when I want the extra security of the Chrome OS platform. Instead, this laptop charges from an old-school 12V barrel connector, forcing me to carry around an extra brick.
What we need is called a “USB-C PD trigger”, a little board that negotiates a specific PD voltage with a charger. There are a few variants, including ones with a button to select the voltage, but the most common one is a tiny board with a female USB-C connector called ZYPDS.
Touch And Go
Pondering the disastrous fate of the HP TouchPad, an early tablet based on WebOS that’s best known for being the subject of a well-remembered fire sale.
TRRespass: Exploiting the Many Sides of Target Row Refresh
Well, after two years of rigorous research, looking inside what is implemented inside CPUs and DDR4 chips using novel reverse engineering techniques, we can tell you that we do not live in a Rowhammer-free world. And we will not for the better part of this decade. Turns out while the old hammering techniques no longer work, once we understand the exact nature of these mitigations inside modern DDR4 chips, using new hammering patterns it is trivial to again trigger plenty of new bit flips. Yet again, these results show the perils of lack of transparency and security-by-obscurity. This is especially problematic since unlike software vulnerabilities, we cannot fix these hardware bit flips post-production.