Recently another antique computer was restored to working condition. Originally called the Harwell Dekatron, the WITCH (Wolverhampton Instrument for Teaching Computing from Harwell) was built in 1949-1951. Back in the early days of computing, it often took years to build a computer, rather then the minutes it takes to make a iPhone in today’s factories.
The WITCH was a decimal computer, storing data not in 0′s and 1′s of the transistor age, but actual decimal digits. It originally could store 20 8 digit numbers (0-99,999,999 or 23 binary bits) but later was upgraded to support up to 40, which was considered more then enough (such short sighted statements did not end in the 50′s, if you’ll remember Bill Gates comment about 640k of RAM is all anyone would need.) Data on the WITCH was stored on Dekatron tubes, a Cold-cathode device filled with Neon (or Argon) that could represent 10 digits. Sending a pulse to the Dekatron would cause the glowing Neon dot (and its associated high voltage) to move from cathode to cathode, thus allowing data to be stored. One side effect of having decimal data, and glowing orange dots for volatile storage is you can literally SEE what is in memory.
Dekatron in operation (courtesy of tube-tester.com)
The WITCH was mainly used to perform mathematical computations. It was not a fast computer, it took it a good 10-15 seconds to perform a multiplication. Many humans with adding machines could actually work the problems faster, however the WITCH never complained of carpal tunnel nor did it need breaks. The Harwell Dekatron was slow, but is was steady and quite reliable. It could go for days (providing it had enough problems fed to it on paper tape) without error or breakdown and that is what made it so useful and worth restoring.
Check out the BBC article and video of its operation and listen to the relays click, and see the glowing Neon of computational history.
Paul Allen, co-founder of Microsoft, has just opened the Living Computer Museum in Seattle. Living, of course, due to the fact that many of the vintage computers on display are working units. Some very rare systems including the only working PDP-7 in the entire world (UNIX was created to run on the PDP-7, so its a rather famous machine) and other DEC’s are on display. There are original IBMs, TRS-80s, Novas, and yes even some Apples. No Apple 1 as of yet. Perhaps Paul could pick up this latest one on auction? Should go cheap as it seems to be lacking an original MOS 6502 CPU.
The HP Input Output Blog has a nice write up on the floppy disk/drive. A very interesting read about a device many took for granted, and many of today’s generation did not ever get to experience. Many do not realize its humble beginnings, and the importance that Steve Jobs, ‘the bum in the lobby,’ played in the 5.25″ floppy becoming a standard. The 5.25″, holding twice what a 8″ floppy could, was developed by Shugart Associated in 1976. Shugart went on to become Seagate, known today for their hard drives. Hard drives that can store over 2 Terabytes of information. The original 5.25″ floppy? 160K, per side. An 8 inch? 80K a side. Interestingly enough, it was sometime before the Floppy Drive Controller (FDC) was integrated onto a single chip. Many original Shugarts used an Intel 8080 CPU for drive processing. The Commodore 64′s famous 1541 Floppy Drive ran its own 6502 type CPU, and was designed in such away you could actually load code directly to the floppy drive 6502. In the 1990′s attempts were made to increase the capacity, speed, and versatility of the floppy. Apple created a 2.88MB 3.5 inch floppy that never really caught on. There was the LS-120 drive which could use normal 1.44MB disks as well as special 120MB disks (was handy, but so few people had them, they had limited use). Ultimately, like most all technology the floppy has passed by the way side, today’s floppy is the USB Flash drive, holding many gigs of data for only a few dollars. And like the floppy, flash drives are used commonly for sneakernetting files around the office. Perhaps the mbile version of the floppy is the Micro-SD card, remember when Sony built a camera with a 1.44MB floppy drive built in? Not een large enough to store the picture from a cell phone camera today.
Yesterday Hans Camenzind passed away at the age of 78. Hans was a notable inventor of Swiss decent. Perhaps the most famous of all his inventions occurred in 1972 while working on a contract with Signetics he invented the 555 Timer chip, a simple oscillating IC that was inexpensive, and easy to build with. Now, even 40 years after its introduction, around a billion per year are still made, by dozens of companies around the world. The 555 Timer is often one of the very first IC’s electronics hobbyist begin experimenting with. Its applications are far reaching and while certainly not a CPU, its significance, and that of Camenzind, should not be forgotten.
The 555 Timer has of course been used in many many computers, notably in the Apple II computer as a joystick controller (558 Timer, which is a quad 555). Other uses include the IBM PC, Ataris, and many many more. In honor of Hans Camenzind, and the 555 Timer, go experiment with one and experience the joys of a device over 40 years old. Dont have one? They cost a whopping $0.95 at Sparkfun.
The Spacecraft CPU page has been updated, after a long gap. It now includes information of the recently landed Curiosity Lander, some new information on the 45 year old Voyager series as well as some on New Horizons, DAWN, and several others, so check it out.
Hard to imagine its been 30 years since IBM released the 5150 Personal Computer for the grand sum of $1265 thus starting the flood of PCs. Build with generic hardware, and MS-DOS from Bill Gates and crew (itself only released a month prior), the 5150 did away with proprietary, the MS-DOS OS was not exclusive to IBM, and the hardware was essentially off the shelf, using Intel’s 4.77MHz 8088 (cut down version of the 8086) processor and a discrete 256k of RAM. Other companies, could, and did, in mass, replicate and add to the 5150 making the 8088, and with it the x86 instruction set the de facto standard even to today. (though ARM has been making a large impact as of late due to the rise of mobile computing)
Here is an early add for the 5150, not only have we come a long ways in computers, but advertising as well.
On April 25th, 1961 Robert Noyce, then working at Farichild Semiconductor, received Patent 2,981,877 SEMICONDUCTOR DEVICE-AND-LEAD STRUCTURE. This was the patent for how to make integrated circuits, containing multiple silicon based transistors, on a single die. Six months prior Jack Kilby received a similar patent, but for geranium based devices. Silicon became, for a variety of reasons, the preferred material and 50 years later we now use some of the same principles to build IC’s with over a billion transistors on them. The diagram in the patent showed a device with 8 components on a single doe, 1 transistor, 2 diodes, 2 capacitors, and 3 resistors.
In 1968 Noyce, and Gordon Moore (of Moore’s Law fame) left Fairchild and founded Intel. Fairchild Semiconductor was the ‘incubator’ of many such semiconductor companies, Intersil, Teledyne, Xicor and AMD were all founded by former Fairchild employees
RCA 1802E Die - 20x magnification - Visual6502.org
The talent at Visual6502.org continues. After imaging and building a complete simulator for the MOS 6502 they did the same for the Motorola 6800 (from which the 6502 was based).
We have sent Visual6502.org several chips and they have now imaged the RCA 1802 that we sent. What is very interesting is how little marking are on the die, the only that I could see was the number ’10824.’ This particular chip was dated early 1981 though the 1802 COSMAC was designed in 1976 and was one of the first CMOS microprocessors. The 1802 had around 5000 transistors (Visual6502 will let us know exactly how many once they are done, and of course what each and every one of them does). For higher res shots and more info see here
Technologizer has published a very interesting article on Osborne Computers, and its founder, Adam Osborne. Osborne computers was started 30 years ago (April 3rd 1981). They were the fastest growing, and fastest failing company in Silicon Valley, impressive even today. Adam Osborne was one of the most important people in Silicon Valley (along with Bill Gates and Steve Jobs). His books in the 70′s are still invaluable resources for collectors, I have several editions of ‘An Introduction to Microcomputers’ which provide an invaluable reference to some of the chip designs of the 1970′s and early 1980′s.
The Osborne 1, the first wildly successful portable, was based on a Zilog Z80A processor and ran the then popular CP/M OS. If it wasn’t for cash flow problems, Osborne computers may very well have still been making computers today. It is also interesting that Mr. Osborne had a habit of picking designs that ended up to be not very successful (he chose the Zilog Z8000 and Intel 8089 I/O processor as ‘Chips of the Year’ in 1980)
In my daily hunt for new processors, and other chips for the museum, as well as information about new chips, I constantly come across interesting chips, in strange locations. Here you will get a chance to learn WHERE many of the chips in the museum come from and what they are.