N8VEM

Last updated

N8VEM was a homebrew computing project. 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.

Contents

In November 2015 the N8VEM project was ended by its creator Andrew Lynch 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 Z80 microprocessor designed to run CP/M and similar operating systems. It was created in 2008 by Andrew Lynch. 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 has also developed boards for other processors including Z180, Intel 80188, MOS 6502, Motorola 6809, 68000 and 68030.

The N8VEM boards are designed with the free KiCad Electronic design automation (EDA) toolset. Printed circuit board routing 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 PPI chips.

The design philosophy encourages low cost development and assembly by hobbyist amateurs using common tools such as 25 watt soldering iron, multimeter, logic probe (optional), and common hand tools. An oscilloscope is recommended but not required. Some basic electronic skills are helpful although the printed circuit boards are designed for relative beginners.

There are numerous N8VEM components available including ECB [1] and S-100 backplane boards, allow 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 has 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 initial design work has been 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 other board projects aim to apply the convenient bus architecture to processor families beyond the 8080/Z80 CPUs for which the bus standard was originally designed: notably 6502, 68000, and later Intel processor types. [2]

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, [3] [4] many of whom are actively involved in designing and prototyping the hardware and software. [5] 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 [6] simulates the N8VEM SBC (along with many other architectures), providing a virtualised development environment that has the speed and flexibility of modern hardware.

Completed N8VEM hardware and software has frequently been displayed at Vintage Computer Festivals. [7] [8]

Single board computers

ECB Bus:

  1. SBC V2 (Z80, UART, PPI, RAM with battery backup, ROM, RTC)
  2. SBC-188 (80C188 10-25 MHz, UART, PPI, RAM with battery backup, ROM, RTC, FDC)
  3. 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)
  4. SBC Mark IV (Z180 processor, 512K SRAM, 512K Flash or 1MB EPROM, RTC, SD Card, 8-bit IDE, RS-232, RS-422, ECB bus)
  5. KISS 68030 (68030 processor up to 32MHz, up to 256M DRAM, 32K SRAM, 512K Flash, ECB bus)
  6. ZetaSBC (via the ECB Shim board)

S-100 bus:

  1. Z80 S-100
  2. m68k S-100 (In progress)
  3. 8086 S-100 (In progress)
  4. 6502/6809 ECB + carrier boards for other cpu's (?)

Other:

  1. 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.

ECB expansion peripherals

There is an active community development forum (N8VEM Google Discussion Group) from which additional board designs have been developed. There is active development of new boards underway.

System software

RomWBW is a popular system software distribution written to execute on N8VEM hardware.

The N8VEM family of hardware are primarily Z80 based microprocessor single board computers, as well as miscellaneous boards which may be combined and placed in an ECB-like bus, enabling the builder to create a custom computer system. These computers are primarily built from discrete components as were computers in the late 1970s and 1980s. The majority of the systems are Z80 based and use the CP/M-80 operating system that was developed in the late 1970s by Digital Research, Inc.

The RomWBW system software is highly configurable and supports all of the Z80 based systems constructed with N8VEM components. The system software is entirely open source and is provided in both machine readable source form and as pre-built images for those wishing to program firmware chips for insertion in the boards.

In addition to the fully implemented operating system with its BIOS (customized for the N8VEM hardware), there are several dozen utility programs that configure and verify the proper operation of system components such as persistent storage in the form of IDE Hard Drives, Compact Flash, and Secure Digital chips.

The CP/M-80 BIOS is written in assembly language and is built using the TASM assembler. Utility programs are written in a variety of languages including assembler, Digital Research RMAC, Aztec C, and Digital Research PLI. These natively hosted programming languages, and tools such as WordStar (a popular editor of the time), execute under the CP/M operating system and read source files stored on memory disk or persistent media such as IDE devices or Compact Flash and Secure Digital devices through the use of an external adapter.

The version 1.x distributions of the system software have been written in a very standard CP/M-80 way and over the course of a half dozen releases has reached a highly stable state supporting the most commonly built configurations in use. The version 2.x operating software was recently released and uses bank switched memory technology to achieve enhanced functionality. Due to the new technology, there are no practical limits on the number of drivers that can be built in. In the future, this will allow for dynamic configuration and will be much more flexible for the users, in many ways similar to the CP/M-80 Plus family of operating systems which also took advantage of memory paging.

In the same way the hardware is open source, the software is provided in source form as well allowing users to both learn how software was written in the early days of microprocessors, but also to write new software using provided tools and documentation available both in the distribution, on the subversion server, and downloadable from a variety of public archives worldwide.

The current owners of the Digital Research, Inc operating systems and language software have licensed it for non-commercial use and the most comprehensive archives can be found at http://www.cpm.z80.de as well as other popular locations and mirrors.

An alternative system BIOS, UNA BIOS, also exists. It has the advantage that a single ROM image can run on all Z80 and Z180 systems. An alternative CP/M implementation, UNA CP/M, takes advantage of UNA BIOS disk and device drivers.

Related Research Articles

<span class="mw-page-title-main">Aster CT-80</span> 1982 personal computer

The Aster CT-80 is a 1982 personal computer developed by the small Dutch company MCP, was sold in its first incarnation as a kit for hobbyists. Later it was sold ready to use. It consisted of several Eurocard PCB's with DIN 41612 connectors, and a backplane all based on a 19-inch rack configuration. It was the first commercially available Dutch personal/home computer. The Aster computer could use the software written for the popular Tandy TRS-80 computer while fixing many of the problems of that computer, but it could also run CP/M software, with a large amount of free memory Transient Program Area, (TPA) and a full 80×25 display, and it could be used as a Videotext terminal. Although the Aster was a clone of the TRS-80 Model I it was in fact more compatible with the TRS-80 Model III and ran all the software of these systems including games. It also had a built-in speaker which was compatible with such games software.

<span class="mw-page-title-main">Motherboard</span> Main printed circuit board used for a computing device

A motherboard is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use.

<span class="mw-page-title-main">Zilog Z80</span> 8-bit microprocessor

The Zilog Z80 is an 8-bit microprocessor designed by Zilog that played an important role in the evolution of early computing. Software-compatible with the Intel 8080, it offered a compelling alternative due to its better integration and increased performance. The Z80 boasted fourteen registers compared to the 8080's seven, along with additional instructions for bit manipulation, making it a more powerful chip.

In computer architecture, 8-bit integers or other data units are those that are 8 bits wide. Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses of that size. Memory addresses for 8-bit CPUs are generally larger than 8-bit, usually 16-bit. 8-bit microcomputers are microcomputers that use 8-bit microprocessors.

<span class="mw-page-title-main">Zilog</span> American manufacturer of microprocessors

Zilog, Inc. is an American manufacturer of microprocessors, microcontrollers, and application-specific embedded system-on-chip (SoC) products.

<span class="mw-page-title-main">Nascom</span> British single-board computer kit

The Nascom 1 and 2 were single-board computer kits issued in the United Kingdom in 1977 and 1979, respectively, based on the Zilog Z80 and including a keyboard and video interface, a serial port that could be used to store data on a tape cassette using the Kansas City standard, and two 8-bit parallel ports. At that time, including a full keyboard and video display interface was uncommon, as most microcomputer kits were then delivered with only a hexadecimal keypad and seven-segment display. To minimize cost, the buyer had to assemble a Nascom by hand-soldering about 3,000 joints on the single circuit board. Later on, a pre-built, cased machine named Nascom 3 was available; this used the Nascom 2 board.

<span class="mw-page-title-main">Single-board computer</span> Computer whose components are on a single printed circuit board

A single-board computer (SBC) is a complete computer built on a single circuit board, with microprocessor(s), memory, input/output (I/O) and other features required of a functional computer. Single-board computers are commonly made as demonstration or development systems, for educational systems, or for use as embedded computer controllers. Many types of home computers or portable computers integrate all their functions onto a single printed circuit board.

<span class="mw-page-title-main">Atari Falcon</span> 1992 personal computer

The Atari Falcon030, released in 1992, is the final personal computer from Atari Corporation. A high-end model of the Atari ST line, the machine is based on a Motorola 68030 CPU and a Motorola 56001 digital signal processor, which distinguishes it from most other microcomputers of the era. It includes a new VIDEL programmable graphics system which greatly improves graphics capabilities.

The CP System II, also known as Capcom Play System 2 or CPS-2, is an arcade system board that Capcom first used in 1993 for Super Street Fighter II. It was the successor to their previous CP System, CP System Dash and Capcom Power System Changer arcade hardware and was succeeded by the CP System III hardware in 1996, of which the CPS-2 would outlive by over four years. The arcade system had new releases for it until the end of 2003, ending with Hyper Street Fighter II.

<span class="mw-page-title-main">Tangerine Microtan 65</span>

The Tangerine Microtan 65 was a 6502-based single board microcomputer, first sold in 1979, that could be expanded into, what was for its day, a comprehensive and powerful system. The design became the basis for what later became the Oric Atmos and later computers. Those later machines have similar keyboard addressing and tape I/O as the Microtan 65. The Microtan 65 has a hardware single step function that can be used for debugging software in both ROM and RAM. The computer was available as ready-built boards or as kits consisting of board and components requiring soldering together.

<span class="mw-page-title-main">STEbus</span> Non-proprietary, processor-independent, computer bus

The STEbus is a non-proprietary, processor-independent, computer bus with 8 data lines and 20 address lines. It was popular for industrial control systems in the late 1980s and early 1990s before the ubiquitous IBM PC dominated this market. STE stands for STandard Eurocard.

<span class="mw-page-title-main">Z-80 SoftCard</span> Processor card for the Apple II

The Z-80 SoftCard is a plug-in Apple II processor card developed by Microsoft to turn the computer into a CP/M system based upon the Zilog Z80 central processing unit (CPU). Becoming the most popular CP/M platform and Microsoft's top revenue source for 1980, it was eventually renamed the Microsoft SoftCard, and was succeeded by Microsoft's Premium Softcard IIe for the Apple IIe.

<span class="mw-page-title-main">BBC Micro expansion unit</span>

A BBC Micro expansion unit, for the BBC Micro is one of a number of peripherals in a box with the same profile and styling as the main computer.

George Morrow was part of the early microcomputer industry in the United States. Morrow promoted and improved the S-100 bus used in many early microcomputers. Called "one of the microcomputer industry's iconoclasts" by Richard Dalton in the Whole Earth Software Catalog, Morrow ran his own computer business, Thinker Toys, Inc., later Morrow Designs. He was also a member of the Homebrew Computer Club.

Technical Design Labs (TDL) was an early producer of personal computers founded in 1976 by Carl Galletti and Roger Amidon. TDL was based in Princeton, New Jersey, USA in the 1970s and early 1980s.

<span class="mw-page-title-main">Heathkit H8</span> 1970s microcomputer

Heathkit's H8 is an Intel 8080A-based microcomputer sold in kit form starting in 1977. The H8 is similar to the S-100 bus computers of the era, and like those machines is often used with the CP/M operating system on floppy disk.

<span class="mw-page-title-main">Single-board microcontroller</span> Microcontroller built onto a single printed circuit board

A single-board microcontroller is a microcontroller built onto a single printed circuit board. This board provides all of the circuitry necessary for a useful control task: a microprocessor, I/O circuits, a clock generator, RAM, stored program memory and any necessary support ICs. The intention is that the board is immediately useful to an application developer, without requiring them to spend time and effort to develop controller hardware.

<span class="mw-page-title-main">Europe Card Bus</span>

The Europe Card Bus is a computer bus developed in 1977 by the company Kontron, mainly for the 8-bit Zilog Z80, Intel 8080 and Intel 8085 microprocessor families.

The P112 is a stand-alone 8-bit CPU board. Typically running CP/M or a similar operating system, it provides a Z80182 CPU with up to 1MB of SRAM memory, 32KB of in-system programmable flash ROM, serial, parallel and diskette IO, and a realtime clock, in a 3.5-inch drive form factor. Powered solely from 5V, it draws 150mA with a 16 MHz CPU clock. Clock speeds up to 24.576 MHz are possible.

References

  1. "N8VEM". Hd64180-ecb.de. Retrieved 2016-04-01.
  2. "S100 Computers". S100 Computers. Retrieved 2016-04-01.
  3. "Rich Cini's Computer Lab - N8VEM SBC". Classiccmp.org. 2016-02-20. Retrieved 2016-04-01.
  4. "First Project: N8VEM Single Board Computer | Nathan's build log". Thomasns.wordpress.com. 2009-10-26. Retrieved 2016-04-01.
  5. "N8VEM computer with a 3Km wireless link". Hackaday. 2009-03-04. Retrieved 2016-04-01.
  6. "Altair Other Operating Systems". Schorn.ch. Retrieved 2016-04-01.
  7. "Vintage Computer Festival". Vintage.org. Retrieved 2016-04-01.
  8. Finnegan, Patrick (2010-09-18). "N8VEM exhibit | Flickr - Photo Sharing!". Flickr. Retrieved 2016-04-01.

Further reading