x86

65 Articles

the SoM module used to power a Dell Mini 1210, in an extended SODIMM form-factor

When Dell Built A Netbook With An X86 System-on-Module

December 18, 2021 by 33 Comments

Just like with pre-touchscreen cellphones having fancy innovative features that everyone’s forgotten about, there’s areas that laptop manufacturers used to venture in but no longer dare touch. On Twitter, [Kiwa] talks a fascinating attempt by Dell to make laptops with user-replaceable CPU+RAM modules. In 2008, Dell released the Inspiron Mini 1210, with its CPU, chipset and RAM soldered to a separate board in an “extended SODIMM” form-factor – not unlike the Raspberry Pi Compute Modules pre-CM4! Apparently, different versions of such “processor cards” existed for their Inspiron Mini lineup, with varying amounts of RAM and CPU horsepower. With replacement CPU+RAM modules still being sold online, that makes these Dell netbooks to be, to our knowledge, the only x86 netbooks with upgradable CPUs.

You could try and get yourself one of these laptops or replacement CPU modules nowadays, if you like tinkering with old tech – and don’t mind having a subpar experience on even Linux, thanks to the Poulsbo chipset’s notorious lack of openness. Sadly, Dell has thoroughly abandoned the concept of x86 system-on-module cards, and laptops have been getting less modular as we go – we haven’t been getting socketed CPUs since the third generation of mobile Intel boards, and even RAM is soldered to the motherboard more and more often. In theory, the “CPU daughterboard” approach could improve manufacturing yields and costs, making it possible to use a simpler large board for the motherboard and only have the CPU board be high-layer-count. However, we can only guess that this wasn’t profitable enough overall, even with all the theoretical upsides. Or, perhaps, Google-style, someone axed this project internally because of certain metrics unmet.

If you think about it, a laptop motherboard is a single-board computer; however, that’s clearly not enough for our goals of upgradability and repairability. If you’re looking to have your own way and upgrade your laptop regardless of manufacturer’s intentions, here’s an old yet impressive story about replacing the soldered-in CPU on the original Asus EEE, and a more recent story about upgrading soldered-in RAM in a Dell XPS ultrabook. And if you’re looking for retrocomputing goodness, following [Kiwa] on Twitter is a must – last seen liveblogging restoration and renovation of a Kaypro someone threw out on the curb.

The Linux X86 Journey To Main()

November 5, 2021 by 7 Comments

Have you ever had a program crash before your main function executes? it is rare, but it can happen. When it does, you need to understand what happens behind the scenes between the time the operating system starts your program and your first line of code in main executes. Luckily [Patrick Horgan] has a tutorial about the subject that’s very detailed. It doesn’t cover statically linked libraries but, as he points out, if you understand what he does cover, that’s easy to figure out on your own.

The operating system, it turns out, knows nothing about main. It does, however, know about a symbol called _start. Your runtime library provides this. That code contains some stack manipulation and eventually calls __libc_start_main which is also provided by the library. Continue reading “The Linux X86 Journey To Main()” →

Software Defined… CPU?

July 19, 2021 by 45 Comments

Everything is better when you can program it, right? We have software-defined radios, software-defined networks, and software-defined storage. Now a company called Ascenium wants to create a software-defined CPU. They’ve raised millions of dollars to bring the product to market.

The materials are a bit hazy, but it sounds as though the idea is to have CPU resources available and let the compiler manage and schedule those resources without using a full instruction set. A system called Aptos lets the compiler orchestrate those resources.

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Where Are All The Cheap X86 Single Board PCs?

June 17, 2021 by 154 Comments

If we were to think of a retrocomputer, the chances are we might have something from the classic 8-bit days or maybe a game console spring to mind. It’s almost a shock to see mundane desktop PCs of the DOS and Pentium era join them, but those machines now form an important way to play DOS and Windows 95 games which are unsuited to more modern operating systems. For those who wish to play the games on appropriate hardware without a grubby beige mini-tower and a huge CRT monitor, there’s even the option to buy one of these machines new: in the form of a much more svelte Pentium-based PC104 industrial PC.

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DOS Gaming PC Gets Necessary Updates

April 17, 2021 by 10 Comments

PC-104 is a standard computer form factor that most people outside of industrial settings probably haven’t seen before. It’s essentially an Intel 486 processor with lots of support for standards that have long since disappeared from most computers, but this makes it great for two things: controlling old industrial equipment and running classic DOS games on native hardware. For the latter, we turn once again to [The Rasteri] who is improving on his previous build with an even smaller DOS gaming rig, this time based on a platform even more diminutive than PC-104.

The key of a build like this is that it needs native support for the long-obsolete ISA bus to be able to interface with a SoundBlaster card, a gold standard for video games of the era. This smaller computer still has this functionality in a smaller package, but with some major improvements. First, it has a floating point unit so it can run games like Quake. It’s also much faster than the PC-104 system and uses less power. Finally, it fits in an even smaller case.

The build goes well beyond simply running software on a SoM computer. [The Rasteri] also custom built an interface board for this project, complete with all of the necessary ports and an ISA sound chip, all while keeping size down to a minimum. The new build also lets him give the build a better name than the old one (although he phrases this upgrade slightly differently), and will also let him expand some features in the future as well. Be sure to check out that first build if you’re new to this saga, too.

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Undocumented X86 Instructions Allow Microcode Access

March 26, 2021 by 19 Comments

For an old CPU, finding all the valid instructions wasn’t very hard. You simply tried them all. Sure, really old CPUs might make it hard to tell what the instruction did, but once CPUs got illegal instruction traps, you could quickly just scan possible op codes and see what didn’t throw an exception. Modern processors, though, are quite another thing. For example, you might run a random instruction that locks up the machine or miss an instruction that would have been valid but the CPU is in the wrong mode. [Can Bölük] has a novel solution: By speculatively executing the target instruction and then monitoring the microcode sequencer, he can determine if the CPU is decoding an instruction even if it refuses to execute it.

Some unknown instructions may have power for good or evil, such as the recently announced undocumented instructions that can apparently rewrite the microcode. We expect to see a post soon on how to reprogram your Intel processor to run as a 6502 natively.

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Oddball X86 Instructions

February 25, 2021 by 66 Comments

David Letterman made the top ten list famous. [Creel] has a top ten that should appeal to many Hackaday readers: the top 10 craziest x86 assembly language instructions. You have to admit that the percentage of assembly language programmers is decreasing every year, so this isn’t going to have mass appeal, but if you are interested in assembly or CPU architecture, this is a fun way to kill 15 minutes.

Some would say that all x86 instructions are crazy, especially if you are accustomed to reduced instruction set computers. The x86, like other non-RISC processors, has everything but the kitchen sink. Some of these instructions might help you get that last 10 nanoseconds shaved off a time-critical loop.

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