The 10 most influential processors

17th Oct 2010 | 07:00

The 10 most influential processors

Where these chips led, others followed

10 most influential processors: 10-6

Almost 40 years ago, Intel announced "a new era of integrated electronics" with the advent of the 4004 processor.

While this might have been the first ever microprocessor, it's hard to think of it as one of the all-time greats. After all, it had a 4-bit architecture, it was clocked at 740kHz (that's 0.74MHz, or 0.00074GHz), and could access just 4kB of program memory, plus 5,120 bits of data storage.

By way of contrast, the smallest 'real' computers of the time were mini-computers typified by the DEC PDP-11/20, which was launched a year earlier. By using much smaller integrated circuits, but lots of them, it had a 16-bit architecture, a 1.25MHz clock, and could address 56kB of memory. The 4004 was a toy in comparison.

Of course, where it led, others followed – in their hundreds. But if the first ever microprocessor didn't have what it takes to earn a place in our hearts and minds, which of its successors did?

We've cast our nets wide to avoid the traditional Intel and AMD battles, and we're not looking for a chip for your modern PC either. Throughout the decades, dozens of semiconductor companies have tempted us with their wares, and many of the names here will be unfamiliar to those who think a computer always means a beige box running Windows.

Our top ten list includes no fewer than six chips that weren't born in the Intel or AMD stables. We've even included one processor that many thought was consigned to the history books but which is alive and well over 30 years on, as well as some chips that have never even been used in a computer. Read on to see our full list.

10. Intel Core

Historically, most people have primarily judged processors by clock speed. This is perhaps a naïve view, but clock speed is certainly an important metric, and for over 30 years, it has continued to grow apace.

From 740kHz in 1971, it has increased tenfold each decade. Surely that should mean we have 10GHz chips in our machines? Sadly not.

In reality, the fastest clocked x86 chip was a 3.8GHz Pentium 4, released in 2005. What drew a halt to this incremental state of affairs was the burgeoning power consumption, which in the case of that 3.8GHz chip had grown to a massive 115W. By limiting the clock speed but using multiple cores instead, power-hungry chips would seem to be a thing of the past – one of Intel's Core 2 chips had four cores, each clocked at 2.267GHz (a total of 9.068GHz – of a sort) and it consumed just 45W.

The Intel Core wasn't the world's first multicore chip (that honour goes to the IBM POWER4 in 2001), nor was it the first multicore x86 processor (that was the AMD Athlon 64 X2), but to many people it epitomises the multicore approach. In the guise of the Core i7, it's today's fastest x86 processor.

9. POWER & PowerPC

The x86 architecture might be dominant on the desktop today, but at one time it had to compete with Alpha, PA-RISC, MIPS, Itanium and POWER. Initially, most of these processor families were used in high-performance workstations and servers, after which Windows was ported to several of them.

In recent years, many have been dropped or sidelined into applications such as games consoles. As a pioneering technology with a proud heritage and a rosy future, one of these processors makes it into our top ten.

Developed by IBM in 1990, POWER was a RISC (Reduced Instruction Set Computer) processor that was first used in the RS/6000 UNIX-based systems. With the PowerPC 620 launched in 1997, it reached the 64-bit milestone long before x86 chips.

Roadrunner

POWER CHIPS:Roadrunner, the world's first petaflop computer, is built around POWER-based cell chips

For 11 years, in its PowerPC variant, it powered Apple Macs. However, perhaps its biggest achievement is that it's now found in many of the fastest supercomputers, including places three, five, eight and nine in the most recent TOP500 list, the league table of the world's supercomputers.

Intriguingly, the POWER-based Cell chip, of which the third-placed Roadrunner supercomputer contains 12,960, is also used in the Sony PlayStation 3.

8. MOS Technology 6502

In 1975, a now defunct company called MOS Technology introduced the 6502 processor. It went on to influence a generation.

Technically, it was nothing special – an 8-bit chip designed by the team responsible for the Motorola 6800, and similar to it in many ways. Where it broke new ground was in its cost. With a launch price of $25, considerably less than equivalent chips from Intel and Motorola, it started a price war.

BBC micro

BBC MICRO:Powered by the 8-bit 6502, the BBC Micro introduced a whole generation to modern computing

This then fuelled the home computer revolution. The 6502 first made its appearance in machines such as the Apple I and II, the Commodore PET, and the Atari. Here in the UK, it first made its presence felt in the BBC Micro. Introduced by Acorn in 1981 and priced at £235, this didn't have the same super-low pricing or mass market appeal as the likes of the Sinclair ZX81, but it had one important thing going for it.

Due to being featured in the BBC's Computer Literacy Project, it became established as the de facto educational computer and sold to schools by the millions. As a result, a whole generation was introduced to computing, and it was all down to the 6502.

7. Intel 80386

Each new x86 generation broke new ground, but the 80386 (the 386 to its friends) represented a quantum leap. The 4-bit chips lasted just a year before being toppled by their replacements, 8-bit architecture held the top spot for six years, and the 16-bit 8086 had just a seven-year innings.

When the 386 appeared in 1985, it introduced the 32-bit architecture that was the status quo for two decades. It wasn't until 2003 that 64-bit x86 chips entered the mainstream, and 64-bit computing still isn't universal today.

There was the instruction set to consider too. Estimates vary, but the 8086 is reckoned to have had around 120 of them, the 286 added around 17 more, and the 386 increased that number to about 200. Adding instructions doesn't mean a computer can do additional tasks, but transferring work from software routines to the processor's hardware can give a performance boost.

When you bear in mind that the 8086 launched at a clock speed of 5MHz, the 286 at 6MHz, but the 386 at 12MHz, you can see why it was the must-have chip of the 80s.

6. AMD Athlon 64

The AMD Athlon 64 takes its place in our league table as the chip that brought 64-bit computing to the masses. No longer would this headline figure be the sole domain of UNIX workstations and servers. As of 2003, desktop PCs could take advantage of a processor with 64-bit registers and 64-bit buses.

But what does that mean in practice? The first advantage is clear. Because data can be operated on in chunks of 64 bits instead of 32 bits, only half as many instructions have to be executed. That's an instant doubling in speed.

Athlon 64

AMD ATHLON 64:The RISC chips were the first to move to 64 bits, but AMD's Athlon 64 brought it to the masses

Then there's the amount of memory that can be accessed. Here the increase is staggering, from 4GB with 32-bit chips to a theoretical 16 Exabytes (that's 16 billion Gigabytes) with 64-bit architecture. Most 64-bit processors – the Athlon 64 included – don't make all 64 bits of the address bus available on external pins, so they can't address this much memory in reality.

However, for the cost of a few pins, they'd be able to store 2GB for every person on Earth. That's why some experts reckon we'll never need to go beyond 64 bits – though we're not betting on it!

10 most influential processors: 5-1

5. PIC Family

You could shell out up to £850 on a processor for a desktop PC, so it might be something of an eye-opener that several members of our fifth-place PIC family of chips sell in bulk for less that 50p.

The PIC10F200 manufactured by Microchip, for example, has a volume price of just 21p! Needless to say, you're not going to get blistering performance from this chip – it's intended for so-called embedded applications, so you're likely to find it hidden away inside a clinical thermometer or a touch-sensitive light switch, rather than a PC.

It has an 8-bit architecture and is clocked at 4MHz. It boasts built-in flash memory for a 256-instruction program, and it has 16 bytes of RAM. What's more, external memory can't be added – not surprisingly, considering this is a 6-pin chip.

Powerful or not though, eight billion have sold to date. It seems that small truly is beautiful.

4. Motorola 68000

Intel was the first to introduce a mass-market 16-bit chip. Motorola came late to the market in 1979, but leap-frogged Intel by going straight to a hybrid 16/32-bit processor – the 68000. That chip powered a generation of Apple Macs, Amigas and late-model Ataris.

Amiga a500

AMIGA A500:The 68000 powered the hugely successful Amigas and in so doing, gained a loyal following who still reminisce fondly about it today / PHOTO: Bill Bertram

Nick Veitch, one-time editor of Amiga Format magazine, recalls: "One great thing I remember about programming the 68k was that it was easy to use the instructions in a variety of addressing modes, which made things a lot easier than the alternatives. I remember old-time hackers comparing it to the PDP (the original hacker machine at places like MIT), rather than the other microprocessors of the day like the Z80."

Whereas the x86 architecture is still going strong, the last member of the 68000 family, the 68060, was launched in 1994. It was later dropped in favour of the PowerPC family.

3. ARM family

British firm Acorn cornered the education market with their 6502-based BBC Micro, and when the world turned to 16-bit computing, it launched its successor machine, the Archimedes, to do the same for a new generation.

Acorn took a bold approach: rather than basing its new computer on established processors from Intel or Motorola, it designed its own 32-bit processor called ARM (originally standing for Acorn RISC Machine, but now Advanced RISC Machine).

By adopting the Reduced Instruction Set Computer (RISC) approach at a time when most of the other semiconductor manufacturers were employing the Complicated Instruction Set (CISC) approach (today's x86 chips employ elements of both philosophies), the ARM chip was well ahead of the competition.

Despite initially having just an 8MHz clock, the first ARM-based systems were much faster than contemporary machines with Intel 80386s or Motorola 68020s, even though the latter were clocked at twice the speed. However, while it was technically superior, the growing momentum of the PC clones proved its downfall, and the last Archimedes was launched in 1992.

That wasn't the end of the ARM processor, though – far from it.

From tiny Acorns

Acorn might be long gone, but it lives on in the form of its former subsidiary ARM Holdings. More importantly, so does its pioneering processor.

ARM processor

ARM POWER:95 per cent of mobile phones worldwide, including the Nokia X6, use ARM processor cores

According to ARM, there are over 15 billion ARM-based chips in existence, powering over 95 per cent of mobile phones and over 25 per cent of all electronic devices. All this is down to that innovative RISC design, as simplicity means low power consumption.

Strangely, none of the four billion RISC cores made every year are actually manufactured by ARM. Instead, ARM licenses its intellectual property to other companies, who then incorporate it into their own designs. That means Nokia mobile phones, for example, contain Nokia-designed chips with an ARM core.

If you bought this processor for yourself, you wouldn't get a chip of silicon, but something that resembles a computer program – defining the core in a way that can be incorporated into a custom chip. You can build one, right?

2. Intel 8086

There's really no surprise in seeing this legendary chip near the top of the list, is there? The 8086 was Intel's first foray into 16-bit computing, while the 8088 was the cut-down version that made its appearance in the IBM PC, and in doing so, changed the face of personal computing forever.

The mid-70s were the heyday of processor development. The microprocessor revolution was less than seven years old when the 8086 entered the world in 1978. But then we were into the third generation after 4-bit and 8-bit designs.

Intel 8086

AMSTRAD:The Amstrad PC1512 used the 16-bit 8086 yet still drove down the cost of personal computing

What's more, the 8086 was clocked at 5MHz, up from the 4004's 740kHz just over six and a half years earlier. But there was a much more fundamental difference. Intel's 8-bit processors did end up inside computers, but none of these early personal computers exactly flourished – the chips really hadn't been designed with domestic applications in mind.

It's widely reported, for example, that one of Intel's first successes for the 8080 was in automated ticketing equipment for metro systems. Whether Intel really expected the new 8086, and its little brother the 8088, to power computers that would compete with minicomputers costing tens of thousands of pounds is unclear – but that's exactly what they did, and they did it phenomenally well.

Price wars

Released in 1981, the first IBM PC was still considerably more expensive than the home computers of the day, and as a result, there's no doubt that it was aimed at businesses rather than consumers.

The appearance of clones changed all that, though, and prices soon started to drop. Here in the UK, Alan Sugar's Amstrad was instrumental in driving down prices when it launched. The PC1512 had an incredibly competitive £499 price when it appeared in 1986.

By including both a floppy disk drive and a monitor, it was the first affordable serious computer. Interestingly, that rough price level has stuck ever since. Whereas today we're getting thousands of times more power for our money, we still owe a lot to that original 8088-based machine.

1. Ziglog ZX80

Back in the early 80s, the UK led the world for home computer ownership. This was due in no small part to the eff orts of one company – Sinclair Research. The ZX80 was the first home computer to break the £100 barrier, and with the ZX81, the price dropped to £69.95 (or £49.95 in kit form).

ZX spectrum

ZX SPECTRUM:This piece of tech makes us get all misty-eyed

Their successor, the ZX Spectrum, gave many people their first real taste of computing and it stayed cheap. Apart from the manufacturer and attractive pricing, all these home computers had one important thing in common – their use of the Zilog Z80 processor.

Blast from the past

The Z80 competed head-on with our eighth-placed chip, the 6502, in the home computer market of the early 80s. Its origin was on the other side of the great Intel-Motorola divide, having more in common with Intel's 8080. Given that it was designed by the 8080's maker Federico Faggin, who left Intel to set up Zilog, this is hardly surprising. Oddly, it seems likely that Faggin never really envisaged the Z80 being used in anything other than embedded applications.

It flourished on domestic machines nonetheless – in addition to home computers from Sinclair, the Z80 was used in such well-known computers as the Tandy TRS-80, the Amstrad CPC and PCW, and the Sharp MZ-80. It's now 34 years since the Z80 first made its appearance and you'd be excused for assuming that the chip is long gone.

In fact, Zilog is still making waves in 2010, something that has contributed in no small part to the Z80 achieving top spot in our league table. Of course, you won't find a Z80 in any modern-day computer – the 16-bit, 32-bit and 64-bit processors have made sure of that.

However, for embedded applications, it's still going strong today, decades after many of its contemporaries have ceased production. Amazingly enough, you can still buy a Z80 lookalike that's identical to its 1976 counterpart.

Zilog's Z84C0006PEG, for example, has a 6MHz clock and is housed in a 40-pin DIP – that's the big old black plastic chip with a row of pins down each of the long edges. Other variants are clocked at higher speeds and look much more like the modern-day components you see today.

High acclaim

Slightly further removed from the original Z80 is the eZ80Acclaim! family of microcontrollers. Containing a Z80 core that's software compatible with the very first Z80, this device also includes on-chip flash memory for the program, RAM and input/output circuitry.

Some family members even have Ethernet capability. You can expect to find it hidden away in vending machines, security systems and sales terminals. So, for kick-starting the home computer revolution of the early 80s while still beavering away behind the scenes 34 years later, we take our hats off to the most influential processor ever. Here's to the next three decades…

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First published in PC Plus Issue 299

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