Notes on the Pentium's microcode circuitry

Most people think of machine instructions as the fundamental steps that a computer performs. However, many processors have another layer of software underneath: microcode. With microcode, instead of building the processor's control circuitry from complex logic gates, the control logic is implemented with code known as microcode, stored in the microcode ROM. To execute a machine instruction, the computer internally executes several simpler micro-instructions, specified by the microcode. In this post, I examine the microcode ROM in the original Pentium, looking at the low-level circuitry.

The photo below shows the Pentium's thumbnail-sized silicon die under a microscope. I've labeled the main functional blocks. The microcode ROM is highlighted...

Ghetto soldering tweezers

[Misc] And other 3D printed accessories

A USB interface to the "Mother of All Demos" keyset

https://invidious.privacyredirect.com/watch?v=DpshKBKt_os

In the early 1960s, Douglas Engelbart started investigating how computers could augment human intelligence: "If, in your office, you as an intellectual worker were supplied with a computer display backed up by a computer that was alive for you all day and was instantly responsive to every action you had, how much value could you derive from that?" Engelbart developed many features of modern computing that we now take for granted: the mouse,1 hypertext, shared documents, windows, and a graphical user interface. At the 1968 Joint Computer Conference, Engelbart demonstrated these innovations in a groundbreaking presentation, now known as "The Mother of All Demos."

Любительское электровакуумное дело. Освоение стекла от крупных ЛДС Т12

Домашние стеклодувные забавы сегодня осложнены добычей недорогих и легкоплавких заготовок-стеклотрубок. Остатки линейных ламп дневного света (ЛДС) разных типоразмеров могут служить их бросовым источником, но повозиться придётся. Главное дело — вдумчивое и аккуратное потрошение заводских ламп — придётся работать с токсичными веществами. Заготовим такое стекло, попробуем применить трубки от крупных ЛДС типоразмера Т12 Ø 37 мм и Т8 Ø 26 мм, собрав из них простую самодельную лампу-индикатор. Читать дальше →

Comments to USTR Opposing Tariffs and Tariff Increases

The United States Trade Representative invited comments from the public this past month to assist them in making recommendations about how to address so-called “unfair trade practices by other countries” and “non-reciprocal trade relationships”. This is the public comment I left today on the USTR docket. I have also submitted similar comments to my senators and representative in Congress.

“I am deeply alarmed by the Trump administration’s decision last week to impose tariffs on Canadian and Mexican goods, as well as further increase tariffs on imports from China. As the CEO of Great Scott Gadgets, a small Colorado-based business that designs,...

Robotron S6130 — Восставший из мертвых

История ремонта этой пишущей машинки тянется уже 8 лет! Шутка что ли, это Самый Первый Артефакт моего YouTube-канала!

Robotron S6130 — многофункциональная пишущая машинка формата A2 на базе процессора Z80, с функцией запоминания набранных текстов во встроенной оперативной памяти, с записью и воспроизведением на магнитофон, а также возможностью приема и передачи текстов с ЭВМ по последовательному порту!

Но, перед тем как появиться у меня, агрегат порядка четырех лет пролежал в сыром, заброшенном помещении на горе заплесневевших книг. За это время питающая ОЗУ резервная батарейка протекла и пожрала дорожки на материнской плате. Коррозией покрылись и ноги ближайших микросхем, ОЗУ. Разумеется, на первом...

The Pentium contains a complicated circuit to multiply by three

This article is available in German at Heise Online.

In 1993, Intel released the high-performance Pentium processor, the start of the long-running Pentium line. I've been examining the Pentium's circuitry in detail and I came across a circuit to multiply by three, a complex circuit with thousands of transistors. Why does the Pentium have a circuit to multiply specifically by three? Why is it so complicated? In this article, I examine this multiplier—which I'll call the ×3 circuit—and explain its purpose and how it is implemented.

It turns out that this multiplier is a small part of the Pentium's floating-point multiplier circuit. In particular, the...

Emulating a PS5 Controller with Cynthion

https://www.youtube-nocookie.com/embed/MMZAyQuZHvs

We’ve recently published the second video in our Cynthion training series, so if you want to go deeper into exploring and experimenting with USB, this is for you. In this video, Martin explains the basics and evolution of Facedancer and demonstrates how to use Cynthion and Facedancer to emulate a PS5 controller. If you haven’t already, check out the first video- Sniffing PS5 Controller Packets with Cynthion.

Repurposing Cisco power supplies

Sometimes you can find a good deal on used power supply from various vendors. In my case it was Cisco C3K-PWR-750WAC and RPS 2300. The problem is, that they don’t output any voltage until they are plugged into device. The question is, how to fool them into thinking they are plugged in. Update: including N2200-PAC-400W

The spec for the supply looks good:

And the interface is following:

You can see, there are some huge terminals which will obviously be power output and then 16 2.54mm pins where the detection will most likely happen. I was thinking how to find out which pins are...

Chinese PoE extractor teardown

I needed to power some cameras using Power over Ethernet but they only supported 12V input, so I ordered some PoE extractors from ali. Here they are for your information.

They both only support 100Mbps over 2 pairs. The wateproofing was quite annoying to remove but not impossible. It seems they both can be modified to support different input/output voltage. As you can see in the pictures, they are both using H6225K step-down regulator in a very similar design.

The circuit mostly corresponds to following schematic found on the internet:

Thank you for your attention.