intel

117 Articles

Benchmarking Chinese CPUs

November 26, 2025 by 25 Comments

When it comes to PCs, Westerners are most most familiar with x86/x64 processors from Intel and AMD, with Apple Silicon taking up a significant market share, too. However, in China, a relatively new CPU architecture is on the rise. A fabless semiconductor company called Loongson has been producing chips with its LoongArch architecture since 2021. These chips remain rare outside China, but some in the West have been benchmarking them.

[Daniel Lemire] has recently blogged about the performance of the Loongson 3A6000, which debuted in late 2023. The chip was put through a range of simple benchmarking tests, involving float processing and string transcoding operations. [Daniel] compared it to the Intel Xeon Gold 6338 from 2021, noting the Intel chip pretty much performed better across the board. No surprise given its extra clock rate. Meanwhile, the gang over at [Chips and Cheese] ran even more exhaustive tests on the same chip last year. The Loongson was put through typical tasks like  compressing archives and encoding video. The outlet came to the conclusion that the chip was a little weaker than older CPUs like AMD’s Zen 2 line and Intel’s 10th generation Core chips. It’s also limited as a four-core chip compared to modern Intel and AMD lines that often start at 6 cores as a minimum.

If you find yourself interested in Loongson’s product, don’t get too excited. They’re not exactly easy to lay your hands on outside of China, and even the company’s own website is difficult to access from beyond those shores. You might try reaching out to Loongson-oriented online communities if you seek such hardware.

Different CPU architectures have perhaps never been more relevant, particularly as we see the x86 stalwarts doing battle with the rise of desktop and laptop ARM processors. If you’ve found something interesting regarding another obscure kind of CPU, don’t hesitate to let the tipsline know!

Unusual Circuits In The Intel 386’s Standard Cell Logic

November 25, 2025 by 7 Comments

Intel’s 386 CPU is notable for being its first x86 CPU to use so-called standard cell logic, which swapped the taping out of individual transistors with wiring up standardized functional blocks. This way you only have to define specific gate types, latches and so on, after which a description of these blocks can be parsed and assembled by a computer into elements of a functioning application-specific integrated circuit (ASIC). This is standard procedure today with register-transfer level (RTL) descriptions being placed and routed for either an FPGA or ASIC target.

That said, [Ken Shirriff] found a few surprises in the 386’s die, some of which threw him for a loop. An intrinsic part of standard cells is that they’re arranged in rows and columns, with data channels between them where signal paths can be routed. The surprise here was finding a stray PMOS transistor right in the midst of one such data channel, which [Ken] speculates is a bug fix for one of the multiplexers. Back then regenerating the layout would have been rather expensive, so a manual fix like this would have made perfect sense. Consider it a bodge wire for ASICs.

Another oddity was an inverter that wasn’t an inverter, which turned out to be just two separate NMOS and PMOS transistors that looked to be wired up as an inverter, but seemed to actually there as part of a multiplexer. As it turns out, it’s hard to determine sometimes whether transistors are connected in these die teardowns, or whether there’s a gap between them, or just an artifact of the light or the etching process.

Comprehensive Test Set Released For The Intel 80286

July 24, 2025 by 23 Comments

Remember the 80286? It was the sequel to the 8086, the chip that started it all, and it powered a great number of machines in the early years of the personal computing revolution. It might not be as relevant today, but regardless, [Daniel Balsom] has now released a comprehensive test suite for the ancient chip. (via The Register)

The complete battery of tests are available on Github, and were produced using a Harris N80C286-12 from 1986. “The real mode test suite contains 326 instruction forms, containing nearly 1.5 million instruction executions with over 32 million cycle states captured,” Daniel explains. “This is fewer tests than the previous 8088 test suite, but test coverage is better overall due to improved instruction generation methods.” For now, the tests focus on the 286 running in real mode. There are no “unreal” or protected mode tests, but [Daniel] aims to deliver the in the future.

[Daniel] uses the tests with the ArduinoX86, a platform that uses the microcontroller to control and test old-school CPUs. The tests aid with development of emulators like [Daniel’s] own MartyPC, by verifying the CPU’s behavior in a cycle-accurate way.

We’ve explored some secrets of the 286 before, too. If you’ve been doing your own digging into Intel’s old processors, or anyone else’s for that matter, don’t hesitate to notify the tipsline.

[Thanks to Stephen Walters for the tip!]

Rhapsody OS is shown in its boot sequence on a monitor; the edge of the motherboard running it is just visible in the right side of the image.

Bringing An Obscure Apple Operating System To Modern Hardware

June 16, 2025 by 17 Comments

During Apple’s late-90s struggles with profitability, it made a few overtures toward licensing its software to other computer manufacturers, while at the same time trying to modernize its operating system, which was threatening to slip behind Windows. While Apple eventually scrapped their licensing plans, an interesting product of the situation was Rhapsody OS. Although Apple was still building PowerPC computers, Rhapsody also had compatibility with Intel processors, which [Omores] put to good use by running it on a relatively modern i7-3770 CPU.

[Omores] selected a Gigabyte GA-Z68A-D3-B3 motherboard because it supports IDE emulation for SATA drives, a protocol which Rhapsody requires. The operating system installer needs to run from two floppy disks, one for boot and one for drivers. The Gigabyte motherboard doesn’t support a floppy disk drive, so [Omores] used an older Asus P5E motherboard with a floppy drive to install Rhapsody onto an SSD, then transferred the SSD to the Gigabyte board. The installation initially had a kernel panic during installation caused by finding too much memory available. Limiting the physical RAM available to the OS by setting the maxmem value solved this issue.

After this, the graphical installation went fairly smoothly. A serial mouse was essential here, since Rhapsody doesn’t support USB. It detected the video card immediately, and eventually worked with one of [Omores]’s ethernet cards. [Omores] also took a brief look at Rhapsody’s interface. By default, there were no graphical programs for web browsing, decompressing files, or installing programs, so some command line work was necessary to install applications. Of course, the highlight of the video was the installation of a Doom port (RhapsoDoom).

This isn’t the first obscure Apple operating system we’ve seen; some of them have even involved updates to Apple’s original releases. We’ve also seen people build Apple hardware.

Thanks to [Stephen Walters] for the tip!

A Forgotten Consumer PC Becomes A Floating Point Powerhouse

February 17, 2025 by 24 Comments

[Michael Wessel] found some of his old DOS 3D graphics software and tried to run it on an 8088 PC. The tale of adding an 8087 co-processor to speed up the rendering was anything but straightforward, resulting in a useful little project.

There was a point around the end of the 1980s when the world of PCs had moved on to the 386, but the humble 8086 and 8088 hung around at the consumer end of the market. For Europeans that meant a variety of non-standard machines with brand names such as Amstrad and Schneider, and even surprisingly, later on Sinclair and Commodore too.

Of these the Schneider Euro PC was an all-in-one design reminiscent of an Amiga or Atari ST, packing a serviceable 8088 PC with a single 3.5″ floppy drive. A cheap machine like this was never thought to need an 8087, and lacked the usual socket on the motherboard, so he made a small PCB daughter board for the 8088 socket with space for both chips.

It’s a surprisingly simple circuit, as obviously the two chips were meant to exist together. It certainly had the desired effect on his frame rate, though we’re not sure how many other Euro PC users will need it. It does make us curious though, as to how quickly a modern microcontroller could emulate an 8087 for an even faster render time. Meanwhile if you’re curious about the 8087, of course [Ken Shirriff] has taken a look at it.

A Die-Level Look At The Pentium FDIV Bug

December 29, 2024 by 10 Comments

The early 1990s were an interesting time in the PC world, mainly because PCs were entering the zeitgeist for the first time. This was fueled in part by companies like Intel and AMD going head-to-head in the marketplace with massive ad campaigns to build brand recognition; remember “Intel Inside”?

In 1993, Intel was making some headway in that regard. The splashy launch of their new Pentium chip in 1993 was a huge event. Unfortunately an esoteric bug in the floating-point division module came to the public’s attention. [Ken Shirriff]’s excellent account of that kerfuffle goes into great detail about the discovery of the bug. The issue was discovered by [Dr. Thomas R. Nicely] as he searched for prime numbers. It’s a bit of an understatement to say this bug created a mess for Intel. The really interesting stuff is how the so-called FDIV bug, named after the floating-point division instruction affected, was actually executed in silicon.

We won’t presume to explain it better than [Professor Ken] does, but the gist is that floating-point division in the Pentium relied on a lookup table implemented in a programmable logic array on the chip. The bug was caused by five missing table entries, and [Ken] was able to find the corresponding PLA defects on a decapped Pentium. What’s more, his analysis suggests that Intel’s characterization of the bug as a transcription error is a bit misleading; the pattern of the missing entries in the lookup table is more consistent with a mathematical error in the program that generated the table.

The Pentium bug was a big deal at the time, and in some ways a master class on how not to handle a complex technical problem. To be fair, this was the first time something like this had happened on a global scale, so Intel didn’t really have a playbook to go by. [Ken]’s account of the bug and the dustup surrounding it is first-rate, and if you ever wanted to really understand how floating-point math works in silicon, this is one article you won’t want to miss.

A Look At The Intel N100 Radxa X4 SBC

July 29, 2024 by 19 Comments

Recently Radxa released the X4, which is an SBC containing not only an N100 x86_64 SoC but also an RP2040  MCU connected to a Raspberry Pi-style double pin header. The Intel N100 is one of a range of Alder Lake-N SoCs which are based on a highly optimized version of the Skylake core, first released in 2015. These cores are also used as ‘efficiency’ cores in Intel’s desktop CPUs. Being x86-based, this means that the Radxa X4 can run any Linux, Windows and other OS from either NVMe (PCIe 3.0 x4) or eMMC storage. After getting his hands on one of these SBCs, [Bret] couldn’t wait to take a gander at what it can do.

Installing Windows 11 and Debian 12 on a 500 GB NVMe (2230) SSD installed on the X4 board worked pretty much as expected on an x86 system, with just some missing drivers for the onboard Intel 2.5 Gbit Ethernet and WiFi, depending on the OS, but these were easily obtained via the Intel site and installed. The board comes with an installed RTC battery and a full-featured AMI BIOS, as well as up to 16 GB of LPPDR5 RAM.

Using the system with the Radxa PoE+ HAT via the 2.5 Gbit Ethernet port also worked a treat once using a quality PoE switch, even with the N100’s power level set to 15 Watt from the default 6. The RP2040 MCU on the mainboard is connected to the SoC using both USB 2.0 and UART, according to the board schematic. This means that from the N100 all of the Raspberry Pi-style pins can be accessed, making it in many ways a more functional SBC than the Raspberry Pi 5, with a similar power envelope and cost picture.

At $80 USD before shipping for the 8 GB (no eMMC) version that [Bret] looked at one might ask whether an N100-based MiniPC could be competitive, albeit that features like PoE+  and integrated RPi-compatible header are definite selling points.