Thursday, July 23, 2009


OpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution (BSD), a Unix derivative developed at the University of California, Berkeley. It was forked from NetBSD by project leader Theo de Raadt in late 1995. The project is widely known for the developers' insistence on open source code and quality documentation, uncompromising position on software licensing, and focus on security and code correctness. The project is coordinated from de Raadt's home in Calgary, Alberta, Canada. Its logo and mascot is a pufferfish named Puffy.

OpenBSD includes a number of security features absent or optional in other operating systems and has a tradition of developers auditing the source code for software bugs and security problems. The project maintains strict policies on licensing and prefers the open source BSD licence and its variants—in the past this has led to a comprehensive licence audit and moves to remove or replace code under licences found less acceptable.

As with most other BSD-based operating systems, the OpenBSD kernel and userland programs, such as the shell and common tools like cat and ps, are developed together in a single source repository. Third-party software is available as binary packages or may be built from source using the ports tree.

The OpenBSD project maintains ports for 17 different hardware platforms, including the DEC Alpha, Intel i386, Hewlett-Packard PA-RISC, AMD AMD64 and Motorola 68000 processors, Apple's PowerPC machines, Sun SPARC and SPARC64-based computers, the VAX and the Sharp Zaurus

Wednesday, July 08, 2009

Processor architectures


ARM is designing and licensing high-performance chips requiring a relatively low power envelope, which would constitute an ideal basis for netbooks, and has touted these as an alternative platform. Despite this, ARM has had very little success in establishing a market for their chips in netbooks, likely because of incompatibilities of their ARM architecture to the established x86 software ecosystem (primarily the dominant Microsoft Windows operating system, Linux is fully compatible). Freescale, a manufacturer of ARM chips, has projected that by 2012 half of all netbooks will run on ARM and there has been much speculation as to a version of the upcoming Windows 7 compatible with ARM. In June 2009 nVidia announced a dozen mobile Internet devices running Tegra, some of which will be netbooks.


Some Ultra-Low Cost netbooks feature a MIPS CPU. The 64-bit Loongson MIPS microprocessor is also used for higher-end applications.


One report at the end of 2008 suggested the typical netbook featured a 3-lb (1.4 kg) weight, a 9-inch (23 cm) screen, wireless Internet connectivity, Linux or Windows XP, an Intel chip, and a cost of less than US$ 400. The x86-compatible VIA Technologies C7 processor is powering netbooks from HP and Samsung. VIA has also designed the Nano, a new x86-64-compatible architecture targeting lower priced, mobile applications like netbooks.

Tuesday, June 30, 2009

Net Work Cards

What is a network card?

A network card (also called a Network Adapter or Network Interface Card, or NIC for short) acts as the interface between a computer and a network cable. The purpose of the network card is to prepare, send, and control data on the network.

A network card usually has two indicator lights (LED's):

* The green LED shows that the card is receiving electricity;

* The orange (10 Mb/s) or red (100 Mb/s) LED indicates network activity (sending or receiving data).

To prepare data to be sent the network card uses a transceiver, which transforms parallel data into serial data. Each cart has a unique address, called a MAC address, assigned by the card's manufacturer, which lets it be uniquely identified among all the network cards in the world.

Network cards have settings which can be configured. Among them are hardware interrupts (IRQ), the I/O address and the memory address (DMA).

To ensure that the computer and network are compatible, the card must be suitable for the computer's data bus architecture, and have the appropriate type of socket for the cable. Each card is designed to work with a certain kind of cable. Some cards include multiple interface connectors (which can be configured using jumpers, DIP switches, or software). The most commonly used are RJ-45 connectors.
Note: Certain proprietary network topologies which use twisted pair cables employ RJ-11 connectors. These topologies are sometimes called "pre-10BaseT ".

Finally, to ensure that the computer and network are compatible, the card must by compatible with the computer's internal structure (data bus architecture) and have a connector suitable for the kind of cabling used.

Friday, June 19, 2009

Video Feature Connector Pinouts.

Pinout details






Dac Pixel data bit 0



bit 1



bit 2



bit 3



bit 4



bit 5



bit 6



bit 7



Dac Clock



Dac Blanking



Horizontal Sync



Vertical Sync















Select Internal Video



Select Internal Sync



Select Internal Dot Clock



Not Used















Not Used



Not Used

And I assume that pins 1 - 12 are outputs, and 17 - 19 are inputs. Is this correct?

The reason is this - I have a Rombo Media Pro+ video digitising card. It chroma keys its output into the vga monitor signal. However, although it is supposed to work with an ET-4000 with Hi-colour RAMDAC, the colours on screen behave as if the top 2 bits of colour information are missing, and red, green, blue signals are swapped around. Rombo has suggested that this may be due to insufficient buffering on the feature connector outputs, and is happy to sell me a buffer device for 50 pounds. I would rather save about 45 pounds, and build my own. I assume it would require (for example) a 74F244 buffer IC(or two).

Wednesday, May 20, 2009

KVM switch problems

There are two problems with VGA and KVM switches: the pin-9 problem and the pin-12 problem.

The pin 9 problem

Some monitors wait for a valid +5V level (TTL) on pin 9, using this signal to detect the computer. If the KVM switch doesn't provide +5V (pin 9 is floating) or pin 9 is missing on the connector of the cable, the monitor will not startup properly (sometimes the I/O light will flash slowly). The solution is to hardwire the console-side pin 9 of the KVM switch to +5V and ensure that the cable between the KVM switch and console has a wired pin 9.

The pin 12 problem

As mentioned under 'Disabling DDC', a machine connected to a KVM switch, but during startup not connected throughout the KVM switch to the console, will fall back to the default (lower) resolution. The solution is to remove the pin from one end of the VGA cable and to disable any plug and play for the monitor. Systems which use X11 to control the display (such as GNU/Linux or *BSD) will need to edit /etc/X11/xorg.conf so that:

Tuesday, April 28, 2009

Random Access Memory

Random access memory (usually known by its acronym, RAM) is a form of computer data storage. Today it takes the form of integrated circuits that allows the stored data to be accessed in any order (i.e., at random). The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.

This contrasts with storage mechanisms such as tapes, magnetic discs and optical discs, which rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than the data transfer, and the retrieval time varies depending on the physical location of the next item.

The word RAM is mostly associated with volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off. However, many other types of memory are RAM as well (i.e., Random Access Memory), including most types of ROM and a kind of flash memory called NOR-Flash.

Thursday, April 16, 2009

Intel integrated circuits

Among the most advanced integrated circuits are the microprocessors or "cores", which control everything from computers to cellular phones to digital microwave ovens. Digital memory chips and ASICs are examples of other families of integrated circuits that are important to the modern information society. While cost of designing and developing a complex integrated circuit is quite high, when spread across typically millions of production units the individual IC cost is minimized. The performance of ICs is high because the small size allows short traces which in turn allows low power logic (such as CMOS) to be used at fast switching speeds.

Monday, April 06, 2009

Intel dual-core x86 CPUs

The Core brand refers to Intel's 32-bit mobile dual-core x86 CPUs that derived from the Pentium M branded processors. The processor family used a more advanced version of the Intel P6 microarchitecture. It emerged in parallel with the NetBurst (Intel P68) microarchitecture of the Pentium 4 brand, and was a precursor of the 64-bit Core microarchitecture of Core 2 branded CPUs.

The Core brand comprised two branches:

1.The Duo (dual-core)
2.Solo (Duo with one disabled core, which replaced the Pentium M brand of single-core mobile processor).

Monday, March 30, 2009

Read-only memory (ROM)

Read-only memory (usually known by its acronym, ROM) is a class of storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified (at least not very quickly or easily), it is mainly used to distribute firmware (software that is very closely tied to specific hardware, and unlikely to require frequent updates).

In its strictest sense, ROM refers only to mask ROM (the oldest type of solid state ROM), which is fabricated with the desired data permanently stored in it, and thus can never be modified. However, more modern types such as EPROM and flash EEPROM can be erased and re-programmed multiple times; they are still described as "read-only memory"(ROM) because the reprogramming process is generally infrequent, comparatively slow, and often does not permit random access writes to individual memory locations. Despite the simplicity of mask ROM, economies of scale and field-programmability often make reprogrammable technologies more flexible and inexpensive, so mask ROM is rarely used in new products as of 2007.

Monday, March 23, 2009

Intel 8088

The Intel 8088 is an Intel x86 microprocessor based on the 8086, with 16-bit registers and an 8-bit external data bus. It can address up to 1 MB of memory. The 8088 was introduced on July 1, 1979, and was used in the original IBM PC.

The 8088 was targeted at economical systems by allowing the use of 8-bit designs. Large bus width circuit boards were still fairly expensive when it was released. The prefetch queue of the 8088 was shortened to four bytes (as opposed to the 8086's six bytes) and the prefetch algorithm slightly modified to adapt to the narrower bus.

Variants of the 8088 with more than 5 MHz maximum clock frequency include the 8088-2, which was fabricated using Intel's new enhanced nMOS process called HMOS, and specified for a maximum frequency of 8 MHz. Later followed the 80C88, a fully static CMOS design, which could operate from DC to 8 MHz. There were also several other, more or less similar, variants from other manufacturers. For instance, the NEC V20 was a pin compatible and slightly faster (at the same clock frequency) variant of the 8088, designed and manufactured by NEC.

Monday, March 16, 2009

Intel 8008

The Intel 8008 was an early byte-oriented microprocessor designed and manufactured by Intel and introduced in April 1972. Originally known as the 1201, the chip was commissioned by Computer Terminal Corporation (CTC) to implement an instruction set designed for their Datapoint 2200 programmable terminal. As the chip was delayed and did not meet CTC's performance goals, the 2200 ended up using CTC's own TTL based CPU instead. An agreement permitted Intel to market the chip to other customers after Seiko expressed an interest in using it for a calculator.

The chip (limited by its 18 pin DIP packaging) had a single 8-bit bus and required a significant amount of external support logic. For example, the 14-bit address, which could access "16 K x 8 bits of memory", needed to be latched by some of this logic into an external Memory Address Register (MAR). The 8008 could access 8 input ports and 24 output ports.

Monday, March 09, 2009

Intel 80386

The Intel 80386, otherwise known as the i386 or just 386, is a microprocessor which has been used as the central processing unit (CPU) of many personal computers and workstations since 1986.

As the original implementation of the 32-bit form of the 8086-architecture, the i386 instruction set, programming model, and binary encodings is still the common denominator for all 32-bit x86 processors. As such, it has remained virtually unchanged for over 20 years, enabling modern processors to run most programs written for earlier chips, all the way back to the original 16-bit 8086 of 1978.

Successively newer implementations of this same architecture have become several hundred times faster than the original i386 chip during these years (or thousands of times faster than the 8086). A 33 MHz i386 was reportedly measured to operate at about 11.4 MIPS.

The i386 was launched in October 1985, but full-function chips were first delivered in 1986[vague]. Main boards for 386-based computer systems were at first expensive to produce but were rationalized upon the 386's mainstream adoption. The first personal computer to make use of the 386 was designed and manufactured by Compaq.

In May 2006 Intel announced that production of the 386 would cease at the end of September 2007. Although it had long been obsolete as a personal computer CPU, Intel, and others, had continued to manufacture the chip for embedded systems, including aerospace technology.

Monday, March 02, 2009

Intel 80286

The Intel 286, introduced on February 1, 1982, (originally named 80286, and also called iAPX 286 in the programmer's manual) was an x86 16-bit microprocessor with 134,000 transistors.

It was widely used in IBM PC compatible computers during the mid 1980s to early 1990s.

After the 6 and 8 MHz initial releases, it was subsequently scaled up to 12.5 MHz. (AMD and Harris later pushed the architecture to speeds as high as 20 MHz and 25 MHz, respectively.) On average, the 80286 had a speed of about 0.21 instructions per clock. The 6 MHz model operated at 0.9 MIPS, the 10 MHz model at 1.5 MIPS, and the 12 MHz model at 1.8 MIPS.

The 80286's performance was more than twice that of its predecessors (the Intel 8086 and Intel 8088) per clock cycle. In fact, the performance increase per clock cycle of the 80286 over its immediate predecessor may be the largest among the generations of x86 processors. Calculation of the more complex addressing modes (such as base index) had less clock penalty because it was performed by a special circuit in the 286; the 8086, its predecessor, had to perform effective address calculation in the general ALU, taking many cycles. Also, complex mathematical operations (such as MUL/DIV) took fewer clock cycles compared to the 8086.

Monday, February 23, 2009

Random Access Memory (RAM)

RAM (random access memory) is the place in a computer where the operating system, application programs, and data in current use are kept so that they can be quickly reached by the computer's processor. RAM is much faster to read from and write to than the other kinds of storage in a computer, the hard disk, floppy disk, and CD-ROM. However, the data in RAM stays there only as long as your computer is running. When you turn the computer off, RAM loses its data. When you turn your computer on again, your operating system and other files are once again loaded into RAM, usually from your hard disk.

RAM can be compared to a person's short-term memory and the hard disk to the long-term memory. The short-term memory focuses on work at hand, but can only keep so many facts in view at one time. If short-term memory fills up, your brain sometimes is able to refresh it from facts stored in long-term memory. A computer also works this way. If RAM fills up, the processor needs to continually go to the hard disk to overlay old data in RAM with new, slowing down the computer's operation. Unlike the hard disk which can become completely full of data so that it won't accept any more, RAM never runs out of memory. It keeps operating, but much more slowly than you may want it to.

Friday, February 13, 2009

Intel 8080

The Intel 8080 was an early microprocessor designed and manufactured by Intel. The 8-bit CPU was released in April 1974 running at 2 MHz (at up to 500,000 instructions per second), and is generally considered to be the first truly usable microprocessor CPU design. It was implemented using non-saturated enhancement-load NMOS, demanding extra voltages.

The Intel 8080 was the successor to the Intel 8008. It used the same instruction set as the 8008 (developed by Computer Terminal Corporation) and was source code compatible. The 8080's large 40 pin DIP packaging permitted it to provide a 16-bit address bus and an 8-bit data bus, allowing easy access to 64 kilobytes of memory.

As the chip was delayed and did not meet CTC's performance goals, the 2200 ended up using CTC's own TTL based CPU instead. An agreement permitted Intel to market the chip to other customers after Seiko expressed an interest in using it for a calculator.

Monday, February 09, 2009

Pioneer 10

Pioneer 10 (also called Pioneer-F) was the first spacecraft to travel through the asteroid belt, which it entered on July 15, 1972, and to make direct observations of Jupiter, which it passed by on December 3, 1973. It was launched from Cape Canaveral Air Force Station's Launch Complex 36A on March 2, 1972. Pioneer 10 is heading in the direction of Aldebaran, located in Taurus. By some definitions, Pioneer 10 has become the first artificial object to leave the solar system. It is surely the first human-built object to have been set upon a trajectory leading out of the solar system. However, it still has not passed the heliopause or Oort cloud.

Its objectives were to study the interplanetary and planetary magnetic fields; solar wind parameters; cosmic rays; transition region of the heliosphere; neutral hydrogen abundance; distribution, size, mass, flux, and velocity of dust particles; Jovian aurorae; Jovian radio waves; atmosphere of Jupiter and some of its satellites, particularly Io; and to photograph Jupiter and its satellites.

Monday, February 02, 2009

Intel 4004

The Intel 4004 is a 4-bit central processing unit (CPU) released by Intel Corporation in 1971. The 4004 is the first complete CPU on one chip, the first commercially available microprocessor, a feat made possible by the use of the new silicon gate technology allowing the integration of a higher number of transistors and a faster speed than was possible before. The 4004 employed a 10 μm silicon-gate enhancement load pMOS technology and could execute approximately 92,000 instructions per second (that is, a single instruction cycle was 11 microseconds).

The 4004 was released on November 15, 1971. Packaged in a 16-pin ceramic dual in-line package, the 4004 is the first computer processor designed and manufactured by chip maker Intel, which previously made semiconductor memory chips. The chief designers of the chip were Federico Faggin and Ted Hoff of Intel, and Masatoshi Shima of Busicom (later of ZiLOG, founded by Federico Faggin).

Monday, January 26, 2009

Digital Equipment Corporation

Digital Equipment Corporation was a pioneering American company in the computer industry. It is often referred to within the computing industry as DEC (this acronym was frequently officially used by Digital itself, but the trademark was always DIGITAL). Its PDP and VAX products were arguably the most popular minicomputers for the scientific and engineering communities during the 1970s and 1980s. DEC was acquired in June 1998 by Compaq, which subsequently merged with Hewlett-Packard in May 2002. As of 2007 its product lines were still produced under the HP name. From 1957 until 1992 its headquarters was located in an old wool mill in Maynard, Massachusetts.

Digital Equipment Corporation should not be confused with Digital Research; the two were unrelated, separate entities; or with Western Digital (despite the fact that they made the LSI-11 chipsets used in Digital Equipment Corporation's low end PDP-11/03 computers). Note, however, that there were Digital Research Laboratories where DEC did its corporate research.

Monday, January 12, 2009

NOR memories

Reading from NOR flash is similar to reading from random-access memory, provided the address and data bus are mapped correctly. Because of this, most microprocessors can use NOR flash memory as execute in place (XIP) memory, meaning that programs stored in NOR flash can be executed directly without the need to first copy the program into RAM. NOR flash may be programmed in a random-access manner similar to reading. Programming changes bits from a logical one to a zero. Bits that are already zero are left unchanged. Erasure must happen a block at a time, and resets all the bits in the erased block back to one. Typical block sizes are 64, 128, or 256 KB.

Bad block management neither is a relatively new feature in NOR chips. In older NOR devices not supporting bad block management, the software or device driver controlling the memory chip must correct for blocks that wear out, or the device will cease to work reliably.

The specific commands used to lock, unlock, program, or erase NOR memories differ for each manufacturer. To avoid needing unique driver software for every device made a special set of CFI commands allow the device to identify itself and its critical operating parameters.

Monday, January 05, 2009

Memory wear

Another limitation is that flash memory has a finite number of erase-write cycles. Most commercially available flash products are guaranteed to withstand around 100,000 write-erase-cycles, before the wear begins to deteriorate the integrity of the storage.[citation needed] The guaranteed cycle count may apply only to block zero (as is the case with TSOP NAND parts), or to all blocks (as in NOR).

This effect is partially offset in some chip firmware or file system drivers by counting the writes and dynamically remapping blocks in order to spread write operations between sectors; this technique is called wear levelling. Another approach is to perform write verification and remapping to spare sectors in case of write failure, a technique called bad block management (BBM).

For portable consumer devices, these wearout management techniques typically extend the life of the flash memory beyond the life of the device itself, and some data loss may be acceptable in these applications. For high reliability data storage, however, it is not advisable to use flash memory that has been through a large number of programming cycles. This limitation does not apply to 'read-only' applications such as thin clients and routers, which are only programmed once or at most a few times during their lifetime.