September 30th, 2017 ~ by admin

Processing the Page Turn

DSC Page Turn Processing Board. 6x 16bit ALUs – 1989

This board isn’t strictly a CPU but it is a processor of sorts.  I actually purchased this board as it was described as a DEC board, with not a great picture, having not seen a DEC board with LOGIC ALUs on it I bought it.  When it arrived I found it wasnt DEC at all but DSC, Digital Services Corporation.  DSC was a video effect company formed in the early 1980’s and later bought out by Chyron, one of the leaders of television video effects hardware.

In the 1980’s, effects on television were generally done in hardware, and required rather specialized hardware for each type of effect.  The most primitive were CG (Character Generators) that added captions typically to the lower third of the screen for a broadcast, like the name of the person speaking, etc.  As hardware capabilities increased, other effects could be generated, such as a video or image overlay, perspective changes or the page turn effect.

Logic L4C381GC-40 – 4x4bit ALU’s implemented in CMOS

These effects generally were handled by an effects processing system, with each effect having its own board in the system responsible for that effect.  Adding an effect required buying an effects board and installing it in the system.  This particular board from DSC handles the Page Turn Effect.  This is where one video transitions to another video with the look of a turning page.  It requires 3 inputs, the first video, the second video being turned to, and a typically solid color/image that represents the back of the page.  Here is a quick example on YouTube.  Today this can be handled by most any video editing software on a general purpose computer, but in 1989 there wasn’t a computer that could do this in near real time.

This board is built around 6 LOGIC L4C381GC-40/55 ALUs and 6x LOGIC LMU216JC-55 Multipliers.  The 4C381s are a 16-bit CMOS ALU, based on 4 74381 4-bit ALU,s a Carry Generator and interface logic.  Basically 1970’s technology updated to CMOS.  They handle 16 bit Addition, Subtraction and basic logic (XOR/OR/AND).  The LMU216s are 16 x 16-bit Parallel Multipliers.  They are the equivalent of the old AMD Am29516 that was cloned by TRW, Cypress and IDT.

LOGIC LMU216JC-55 – 16×16 CMOS Multiplier

The rest of the board consists of 6x64Kb or Video RAM, shift registers, and all the control logic (in PALs) to provide the instructions for the ALUs and multipliers.  The arrangement of the board suggests a 64-bit computation section and a 32-bit section.  Just as in the 1970’s the ALUs and multipliers have been used to make a custom processor, with a very specific instruction set and purpose and do so at a speed that would be compatible with broadcast television.  Sitting on one’s couch in the 1980’s watching TV and seeing a cool page turn effect one would think, ‘Hey that’s cool!’, yet have no idea that an entire processing system had to be designed, built and coded for that one second of television.

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CPU of the Day

February 13th, 2016 ~ by admin

RCA CDP1855: A Multiplier for the COSMAC

RCA CDP1855CE - 3.2MHz @ 5V

RCA CDP1855CE – 3.2MHz @ 5V

In the 1970’s MULT/DIV instructions were fairly uncommon to be implemented in hardware on a processor.  They were implemented in software (usually be the compiler, or hand coded) as a series of adds and subtracts/shifts.  In some cases dedicated hardware, usually through a series of bit slice processors, or ‘181s were added to handle MULT/DIV requirements.

In 1978 RCA announced the CDP1855 Programmable Multiplier/Divider for the 1802 COSMAC processor.  Sampling began in 1979, making this one of the earliest ‘math coprocessors’ of the time.  The 1855 was an 8×8 Multiplier/Divider, handling Multiplies with Addition/Shift Right Ops, and Division using Subtractions/Shift Left Ops.  It was, like the COSMAC, made in CMOS, and at 10V ran at 6.4MHz, allowing for a 8×8 MULT to finish in 2.8us.  The CDP1855 was also designed to be cascaded with up to 3 others, providing up to a 32×32 bit multiply, in around 12usec, astonishing speed at the time.  Even the slower CDP1855CE (using a 5V supply and clocked at 3.2usec) could accomplish a full 32×32 MULT in 24usec.  An AMD AM9511 (released a year earlier) can do a 32×32 fixed point multiply in 63usec (@ 3MHz).

Soviet Integral 588VR2A - CDP1855 'Analog' from 1991

Soviet Integral 588VR2A – CDP1855 ‘Analog’ from 1991

The CDP1855 was designed to interface directly with the 1802 processor, but could be used with any other 8-bit processor as well.  It was programmable, so the host processor only needed to load with the data to be multiplied/divided, the control values ot tell it what to do, and then wait for the results.

As was typical, the Soviets made an ‘analog’ of the CDP1855 called the 588VR2 and 588VR2A.  The 588VR2 was packaged in a 24-pin package vs the 28 pins of the CDP1855, so its certainly not directly compatible.  Soviet IC design houses were instructed and paid to design and make copies of Western devices, typically original ideas were discouraged.  This led to a lot of devices being made that were similar, but not the same as their Western counterparts, the design firm could make a somewhat original device, and then simply claim to the bureaucrats that it is an ‘analog’ to a certain Western design.  Thus the 588VR2 is ‘similar’ or an ‘analog’ to the 1855.

The CDP1855 continued to be made, and sold into the late 1990s, much like the 1802 processor it supported.


May 16th, 2013 ~ by admin

ALU of the Day: Bipolar B2120A-30

B2120A Floating Point ALU 1989 33MHz

B2120A Floating Point ALU 1989 33MHz

Bipolar Integrated Technology Inc. (BIT) was founded in 1983 in Beaverton Oregon by former Floating Point Systems, Intel, and Tektronix engineers.  Their goal was to develop fast floating point processors based on a bipolar process (rather then the more common NMOS and CMOS of the time.  The bipolar process is used to make TTL, and ECL type products, and had been used in several previous processors, including the AMD 2901 and the SMS300 (Signetics 8X300).

The B2120 was part of a complete floating point chip set that was released in 1987.  the B2120 handled all the ALU functions, while the B2110 was the multiplier.  It was designed by Bob Elkind who was one of the original employees of BIT and oversaw the development, layout, and packaging of most of their early products. The B2120 was a TTL compatible device while the B3120 and B3110 made using ECL 10KH instead.  Both were made using Bipolar’s proprietary P111 1.2 micron process.  The B2120A-30 had a typical cycle time of 30ns, giving it an effective clock rate of 33MHz.

In 1990 BIT introduced the B2130 (TTL) B3130 (ECL 10KH) and B4130 (ECL 100k) which were 100MHz single chip versions of the 2110/2120

BIT would later make a SPARC chipset called the B5000 (which at 80MHz was the fastest processor of its time) and a follow on version called the B6000.  Both were made using ECL. Reliability problems and the eventual catchin up of CMOS in speed led to their demise, and in 1996 BIT was purchased by PMC-Sierra (who ended up consolidating a lot of 80’s and 90’s companies).



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CPU of the Day

March 16th, 2013 ~ by admin

ALU of the Day: Motorola MC14581CL – Logic 4 bits at a time

Motorola MC14581CL 4-bit ALU

Motorola MC14581CL 4-bit ALU – 1973

At the heart of every processor is an ALU, an Arithmetic Logic Unit.  It is what does the addition, subtraction, compares, and other logic function on the bits we call data. Add some memory for registers, stack, and program control and one has a basic processor, or bit slice processor.   In the 1970’s and even the 1980’s many systems still implemented their ‘processor’ in discrete logic.  The 74181 (TTL), 10181 (ECL) and 14581 (CMOS) were the heart of many of them.  The ‘181 could handle any of 16 arithmetic and logic functions on a pair of 4 bit words.

The Motorola MC14581CL was the first of the CMOS ALU’s.  This example was made in early 1973. CMOS itself was only patented a few years prior (1967) and didn’t see extensive use in processors until the mid 1970’s (RCA 1802) and most other processors in the 1980’s.  Remarkably, after 40 years, its still in its original package.


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CPU of the Day

February 17th, 2011 ~ by admin

The AMD 2901 Bit Slicer and Second Sourcing

AMD AM2901ADC – 1977

In August 1975 AMD introduced the ‘100 ns Bipolar microprocessor.’ This was a bit-slice device. Essentially a 4-bit ALU (like a 74181) with functionality (scratch pad memory and accumulator register) to make it work as a processor that could be scaled to any bit width (using the 2909 sequencer and 2910 controller).  Being made in bipolar allowed for the high speed (10MHz at the time was pretty quick).  The introduction of the 2901 also marked the beginning of the end to the competition int he bit-slice arena.  A combination of marketing, second-sourcing, and a good product allowed AMD to completely dominate the bit-slice market.  Even today most bit-slice designs are based on the 2901 from 35 years ago.

At the time there were several other bit-slice processors on the market.  Intel had the 3002 (a 2-bit design), National’s IMP-8 and IMP-16, and the original TTL 74181 were all bit-slice devices.  MMI (which AMD bought in the 1980’s) had introduced the 6701 4bit slice in 1974, a full year before AMD’s 2901.  TI had the SBP0400A and Motorola the MC10800 (in ECL – 1976). So why with all this competition did AMD come to dominate?

Raytheon AM2901ADC – 1980

Second Sourcing

Second sourcing is the licensing of a design to other companies for them to manufacture, market and sell it.  Sometimes its simply a license to manufacture, sometimes it comes with technical assistance, or even complete mask sets to make the device.  There are three main reasons this is done (or was done back in the day)


Guaranteed Availability.

In the 1970’s making IC’s was a relatively new process, one with many bugs, and often reliability issues.  Having a second source was a must to get a big design win. A system design would not want to design a system around a chip that may end up not being available, or not be available in the quantities needed.  Having a second source to get the IC from alleviated this problem.  It gave system designers a stable supply, regardless if the primary source could not keep up, or had a problem.



Second-sourcing helped solve distribution problems as well.  A company may have an excellent design, but no way to sell it.  Often this was a geography problem.  American companies did not initially have a large presence, or distributors set up, in Europe or Japan.  An American company would often second-source a design to a European company (such as Siemens or Thomson) solely to get their design distributed in that area.



One of the keys to a processors success is design wins.  It can be the best processor on the market,. but if no one uses it, it will fail.  Having additional companies make, and market the processor vastly increased its exposure.  Second-source companies would also typically make development systems, and other support tools, as well as vast documentation for the processor.  This helped ensure that engineers knew about the processor, how to use it, and whee to get it, ensuring its winning of more sockets.

Soviet Electronika 1804VS1 – 2901 Clone – 1988

AMD clearly understood the importance of second-sourcing.  In November 1975, just months after the 2901 was released, they designed an agreement with Motorola to make the 2901.  In December, they signed up Raytheon, and in March of 1976 AMD signed an agreement with the SESCOSEM division of Thomson-CSF, to make and distribute the 2901 in markets outside the US and Japan. In June 1976 AMD amended their agreement with Motorola to include more technical assistance, ensuring Motorola could get the 2901 to market. In September 1976 MMI canceled the 6701, as they were unable to compete.  MMI had no second-sources for the 6701 which likely led to its failure.

As the years went by, AMD added more second-sources, and dropped a few. Eventually coming to completely dominate the bit-slice market.  The Soviets began to copy the 2901 around 1985 (not particularly legally but they did what they had to) and continued to do so until well into the 90’s.

Year Second Sources
1975 Motorola
1976 Motorola, Raytheon, Thomson
1977 Motorola, Raytheon, Thomson, National
1978 Motorola, Raytheon, National, Fairchild, NEC, Signetics, Thomson
1980 Motorola, Raytheon, National, Fairchild, NEC, OKI (MSM8821?), Thomson
1982 Motorola (2903), National, Fairchild, NEC, Thomson
1985 National, Thomson, Cypress, USSR
1990 Cypress, IDT, Thomson, National, USSR
1995 Cyrpress, IDT, WSI, Thomson, Russia

Innovasic IA59032 – 8 x 2901 – 2003

AMD also made the AM29C101 which was 4 2901s in a single chip, producing a 16bit processor.  Cypress manufactured a copy of the 29C101 called the CY7C9101

Several other companies also designed multiple 2901s into a single chip. WSI (and later InnovASIC) designed the 59032, which has the equivalent of 8 2901s to form a 32 bit slice and the 59016 which was  16bit slice (4x 2901).  IDT designed the 49C402 which was also a 16 bit slicer.  Today the 2901 is still in wide use, and while not generally used for new designs, it still powers a vast amount of electronic equipment that still is in use.  InnovASIC still manufactures the 2901 (in 59032 form) to this day.

September 23rd, 2010 ~ by admin

Arithmetic Processors: Then and Now

In the beginning there was the microprocessor.  A collection of logic that centered around an ALU (Arithmetic and Logic Unit) and a series of registers.  It was capable of doing most tasks just fine.  Simple math, and boolean logic were the key to most programming needs.  As the life of the processor and its extension, the microcontroller, progressed the computing needs became larger.  Programmers wanted to be able to manipulate larger numbers, and floating point ones at that.  Add and Subtract were no longer sufficient, division, multiplication and a host of other mathematical functions were needed.  In the 1970’s transistor counts were in the thousands, frequency in the MHz and line widths were measured in microns.  It was not feasible to build these math functions, in hardware, on the same chip (or rather die) as the processor.

AMD AM9511DM - 2MHz Military Temp Range APU - 1978

Several companies worked to solve this.  Perhaps the most successful, and famous, was AMD.  AMD in 1977 introduced the AM9511 Arithmetic Processing Unit.  It is best described as a scientific calculator on a chip. It could handle 32 bit double precision math (via 16 bit stack/registers) and supported not just the basic ADD, SUB, MUL and DIV, but SIN, COS, TAN, ASIN, ACOS, ATAN, LOG, LN, EXP, and PWR. 14 floating point instructions, in hardware, on a single chip.  It ran at up to 3MHz (4MHz in the ‘A’ version) and could interface with pretty much any microprocessor or microcontroller, providing much needed processing power.  It was designed as a peripheral, so that the main processor could assign it a task, and then go on about its program while the AM9511 crunched the math.  The AM9511 would then notify the host processor via interrupt that it was finished the the data/status was ready to be read.

AMD updated the design to support……

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