N8VEM

Key takeaways

N8VEM belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect N8VEM to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of N8VEM from memory before moving on to harder problems.

Reference excerpt

N8VEM was a homebrew computing project created in 2008 by Andrew Lynch. It featured a variety of free and open hardware and software. N8VEM builders made their own homebrew computer systems for themselves and shared their experiences with other homebrew computer hobbyists. N8VEM homebrew computer components are made in the style of vintage computers of the mid to late 1970s and early 1980s using a mix of classic and modern technologies. They are designed with ease of amateur assembly in mind. In November 2015, Lynch ended the N8VEM project, and the community reconvened under the new name of Retrobrew Computers.

Creation and operation

There are several N8VEM designs starting with a single-board computer carrying a Zilog Z80 microprocessor designed to run CP/M and similar operating systems. Contrasted with the P112, which has some surface-mount components, the N8VEM SBC uses only through-hole components, consistent with the design philosophy that building should be within the skills and resources of non-professional hobbyists. The project also developed boards for other CPUs, including the Zilog Z180, the Intel 80188, the MOS Technology 6502, and the Motorola 6809, 68000 and 68030. The N8VEM boards were designed with the free KiCad electronic design automation (EDA) toolset. Printed circuit board routing was provided by FreeRouting.net. Software is developed in Z80/8085 assembly language using the MS-DOS Telemark Cross Assembler program (TASM), as well as the open source Small Device C Compiler. A major design goal is to use freely available tools to the maximum extent possible. The printed circuit board design is supplemented using component libraries available at KiCad Libraries, specifically the Zilog Z80 CPU and Intel 8255 Programmable Peripheral Interface (PPI) chips. The design philosophy encourages low cost development and assembly by hobbyist amateurs using common tools such as a 25-watt soldering iron, a multimeter, a logic probe (optional), and common hand tools. An oscilloscope is recommended but not required. Some basic electronics skills are helpful, although the printed circuit boards are designed for relative beginners. There are numerous N8VEM components available including ECB and S-100 backplane boards, allowing processor and expansion boards to be connected. Other components include video boards, disk controllers, peripheral expansion, and prototyping boards. In response to interest from members, the N8VEM homebrew computing project collaborated in developing a range of boards for the S-100 bus. These can be used to build new systems from scratch on that historic industry standard platform, or to restore and enhance vintage S-100 systems preserved from the 1970s and 1980s. Most of the S-100 board's initial design work was contributed by John Monahan of s100computers.com, with board layout, prototyping and testing contributed by Andrew Lynch and other N8VEM supporters. Some of these S-100 boards provide enhanced capabilities beyond what was available on original S-100 machines, some are replacements for historic S-100 boards, and others aim to apply the convenient bus architecture to processor families beyond the 8080/Z80 CPUs for which the bus standard was originally designed: notably, the 6502, the 68000, and later Intel CPUs. N8VEM is notable for being the largest and most active homebrew computing community in existence today. The project is entirely non-commercial and is made up of over 350 hobbyists, many of whom are actively involved in designing and prototyping the hardware and software. The community is a modern-day version of the historic Homebrew Computer Club frequented by Steve Wozniak and other pioneers of home computer development. Printed circuit boards of the mature designs are manufactured in small batches on a collective order basis, and distributed to members for the cost of the board manufacturing and shipping. The project does not provide complete kits—builders must procure their own parts to populate a board. Support is purely on a volunteer basis through a Google Group and wiki. Software is open source and freely available for download from the wiki. The project was careful to keep things within the reach of the amateur computer hobbyist by using low cost and readily available components that can be assembled with simple hand tools. In addition, notable freeware system emulator SIMH simulates the N8VEM SBC (along with many other architectures), providing a virtualized development environment that has the speed and flexibility of modern hardware. Completed N8VEM hardware and software has frequently been displayed at Vintage Computer Festivals.

Single board computers ECB Bus:

SBC V2 (Z80, UART, PPI, RAM with battery backup, ROM, RTC) SBC-188 (80C188 10-25 MHz, UART, PPI, RAM with battery backup, ROM, RTC, FDC) N8 Home Computer (Z8S180 33 MHz, UART, ROM, RTC, Dual Interrupt controllers, Floppy, SD Card, 1MB RAM, AY-3-8910 sound, TMS9918A video, ECB bus) SBC Mark IV (Z180 processor, 512K SRAM, 512K Flash or 1MB EPROM, RTC, SD Card, 8-bit IDE, RS-232, RS-422, ECB bus) KISS 68030 (68030 processor up to 32MHz, up to 256M DRAM, 32K SRAM, 512K Flash, ECB bus) ZetaSBC (via the ECB Shim board) S-100 bus:

Z80 S-100 m68k S-100 (In progress) 8086 S-100 (In progress) 6502/6809 ECB + carrier boards for other cpu's (?) Other:

SBC6120-RBC: A new edition of the Spare Time Gizmos SBC6120 Model 2 updated to use easily available RAM and EEPROM components, only two PCB layers, and KiCAD.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with N8VEM

Start with the simplest possible case. Write down what N8VEM claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to N8VEM before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about N8VEM ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of N8VEM

In research: N8VEM appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses N8VEM in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: N8VEM is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer-related introductions in 2008, Free and open-source software, Open computers, so understanding it makes those chapters shorter.
In everyday life: Look for N8VEM outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study N8VEM in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what N8VEM means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain N8VEM out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is N8VEM in simple terms?

N8VEM was a homebrew computing project created in 2008 by Andrew Lynch. It featured a variety of free and open hardware and software.

Why does N8VEM matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study N8VEM?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on N8VEM.