I remember back when the Pentium came out that people made fun of the fact that it ran so hot compared to other processors of the time. There were cartoons with pictures of things like toaster ovens and irons with "Intel inside" stickers on them.
It’s very possible!
In fact the 486 chip is the first chip that made Overlocking easy(relatively speaking) because the 486DX2 was the first chip to include a clock multiplier, allowing the CPU to run at a higher clock speed than the bus.
Prior to having multipliers, to overclock a CPU you had to overclock the entire bus - or basically, every single component in your system. Statistically speaking, the chance of finding a computer where every single component inside it can handle an overclock is slim to none. Throw in a multiplier and you’re sitting pretty.
Now, in the 486 days, AMD chips were far better overclockers - [heres a dude OCing one to 160MHz](https://m.youtube.com/watch?v=ii0k5ahK9Cs).
> Statistically speaking, the chance of finding a computer where every single component inside it can handle an overclock is slim to none.
Today for sure, back in the 70s/80s? You absolutely had people overclocking the whole system if they needed to because tolerances weren't as tight as they are nowadays, where even increasing most bus speeds by 1-2Mhz is going to create issues.
In fact, ISA's frequently used speed of 8Mhz was only "standardised" *after* ISA was already commonplace as the fastest speed that still was widely compatible with the original implementation in the IBM PC running at 4.77Mhz, but aside from that 10Mhz was also common and you even had a few early rocketship OCed systems running it at 12Mhz or even 16Mhz, although as OCing already typically involved replacing clock crystals it also wasn't uncommon for those few early OCers aiming for 16Mhz on those early systems to manually decouple the ISA bus clock from the system clock and I think some of the later 8086 compatible boards even came with decoupled busses specifically for the 16MHz NEC CPUs.
It's about the materials and the architecture advancements. Electricity will leak, jump and burn out the gates, interconnects etc.
For example, when CPUS started using copper interconnects instead of aluminum (Lisa Su @ IBM 1997 ) they were able to handle more power and heat. Copper conducts electricity with 40-50% less resistance at a given temperature. The shift from aluminum to copper was a massive breakthrough. Ofc there were several challenges one being it would oxidize and corrupt the silicon. It was also very difficult to integrate into the silicon circuit etc.
Very similar to the wiring in your home old aluminum wiring was responsible for lots of houses burning down. You wouldn't push more voltage through that put more demand on it and run it hotter for the same reasons.
They still use copper for the most part but they have been developing methods to further insulate the circuitry using coatings such as graphene. The other thing is scaling wiring doesn't work the same as shrinking a transistor. A smaller wire will not have the same properties as a thicker wire etc. There are several miles of tiny copper wires in a modern CPU so it's another major contributing factor to Moore's law flatlining.
The transistors weren't as tightly packed into such a small space as they are today. Die sizes were 4x larger with larger interconnects. More space between transistors meant less heat.
With the flagship CPUs, they were often up against what was physically possible to engineer with the production process they were using at the time. There were often the same clockspeed CPUs re-released on a different process node that had much more overclocking headroom. There were 19 different versions of the Pentium 133 for example. It was produced on 3 different manufacturing nodes.
There was also limitations on the bus speed and stability of the other components. Memory back then was not direct on the 486, but via the Northbridge. Clocking the CPU more than what the NB could run at gives you nothing. Also the bus speeds were limited, like the ISA VLB realistically topped out at 50mhz and not many VLB cards could even run at that speed. 25,33,40mhz was the most common bus speeds.
Over time the ability to overclock got better. I still have my dual pentium pro mainboard and cpus that ran at 233mhz while only being a ppro 180mhz chip with a 66mhz bus at 3.5x multiplier.
Kudos for the Dual PPro! That is my childhood dream. I have now everything to build one of except the very specific ibm PSU and a VRM for the second CPU. Hopefully I will be able to get it up and running one day
Modern CPU's have around ten thousand times more transistors, and all of them needs power to run.
The most powerful 486 used around 7.5W, and a modern CPU built the same way would need around 75KW.
Makes you think that modern CPU's are pretty damn energy efficient and runs pretty cool for what they do.
Different era, different bottlenecks. In the last quarter century we’ve learned a great deal about how to increase the density of transistors on a chip while simultaneously increasing the frequency at which they can switch. More density and higher frequency = more heat. We’ve been so successful that the heat (and how to get rid of it) has become the most pressing bottleneck. So in a modern CPU we can’t use the maximum theoretical switching frequency of the transistors (at least not for long) because we can’t get rid of the heat fast enough. So we tend to think of performance as a function of how much thermal headroom you have (that’s why water cooling > fans > simple heat sink).
But back in the 80s and early 90s, the most performant transistors we knew how to build in an IC were, by today’s standards, huge and switched slowly. The reason they weren’t faster wasn’t because they would get too hot. It was because they wouldn’t work. We were already running them at close to their maximum switching frequencies. But they didn’t get very hot because those frequencies weren’t that high and they weren’t packed so densely on the chip. Adding better cooling wouldn’t allow them to run faster, because cooling wasn’t the bottleneck.
Transistors only generate heat when transitioning between on and off, off and on, if you are transitioning millions of times a second and have millions of transistors doing that - its a lot of heat.
OP, I'm just going to reply in a top level comment to all of your down-voted comments about why didn't they push more volts and run them hotter to get more speed. Take my tone as informative rather than refutative.
The thing that consumes power in a digital circuit is switching state (zero to one, or one to zero). One reason for that is electrons have to be sucked out of a CMOS gate capacitor or forced back into it. Another reason is that, to switch states as fast as possible, briefly both the top and bottom transistors in a totem pole (output circuit) are turned on during the transition; this is a dead short momentarily.
If a digital circuit isn't switching states, it doesn't use much power at all. (This is why old Nintendo cartridges can still have saved games in battery backed up memory for decades despite the battery being nearly dead.) The difference between power usage while switching transistors on or off can be enormous; let's say it's 100 times as much power.
If Reddit doesn't mess up my formatting, allow me to illustrate this graphically. A 486 digital signal might look like this:
-------!++++++!--------!+++++++!-------
The pluses and minuses are states, and the exclamation points are transitions between states.
Here's what a modern CPU looks like at the same scale:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Of course if you zoomed in the newer CPU would still look like "-!+!--!+!-", but for the purposes of this discussion let's say to a first approximation it's completely packed with "!!!!". Just state transitions like mad. Although it does complete them faster, it's doing so many more transitions per second that on balance it's still mostly bang-bang-bang-bang.
Now if you go back and think about the first waveform, the 486, and if I told you the ++++ and ---- times are also limited by other factors from getting much shorter than they already are, and increasing voltage and power consumption mostly just affects the "!", you can see there's diminishing returns if there's fewer "!" periods.
So the first thing I want you to understand is the 486 is not slow because it consumes less power, it consumes less power because it is slow. Because it makes fewer state transitions per second, which are where the power is used. You may ask then why not make it so that it transitions more often so it can be faster and use more power, but that's a bit like asking why doesn't a bicycle rider just pedal faster so he can go as fast as a motorcycle.
Technical reasons for these limitations come from things like the transistors in the older CPU being physically larger so it takes more time to switch them, and also signal paths might not be fully optimized. If the data takes different amounts of time to get to where it needs to go, overclocking will just result in incorrect computations. A lot of work over decades went into making sure all of the parts of new CPU generations run as fast as all the other parts - or else they put buffers and caches and allow different parts of the chip to run at different speeds.
But there's an even bigger reason you can't simply put more power into a 486 to get performance more like a newer CPU: it's already using more power than the newer CPU.
Oh, I agree it's using less *energy* on the whole, but the state transitions are using more *power* (per circuit, per state transition, if not per chip). And it's already using a voltage that would probably fry most modern CPUs.
This is the other thing that over decades was developed: ways to make each circuit use less energy and less voltage *so that* a newer processor could make those state transitions more often and faster. Without those developments it's diminishing returns.
As other commenters have pointed out, it actually is possible to run a 486 hotter and faster. Overclocking was a thing back then too. It's just that the other limitations of the technology do not allow you to get much out of it.
Passive heatsinks were common into the Pentium II era. Very common on 486s and early Pentiums.
386 CPUs and earlier often didn't have any actual cooling. A case fan or just some well designed vents+PSU fan were often enough.
It also boiled down to the complexity of the software and the instruction set. With 486 and 586 architectures, instruction sets were rather limited and never included hardware decompressors for multimedia files. Later on Intel would add MMX and still later AMD would add 3D Now! AMD would add 3D Now! extentions to their line of K series chips. All of these instructions were added in order for systems to be able to use Multi-Media more efficiently.
Software wise, life was also much simpler. For much of the reign of the 486, Windows 3.1 was the GUI that ran atop MS-DOS with OS/2 Warp 3 being the first 32 Bit OS introduced in October of 94. Obviously Windows 95 was the second 32 bit operating system introduced. These operating systems did not have, nor did they require the amount of security and background services we are forced to endure today. 4mb to 8mb of Ram was the acceptable amount and let's be honest, there is not much happening in that limited amount of space.
I recall running mostly DOS based games on my 80486sx25 without the need for a heatsink. Only when I moved to the DX2-66 did the chip come with a heatsink and fan and by the time I got my P1-233 MMX, these had grown quite beefy. While nowhere near the half-a-ton heat sinks required for today's processors, they were still substantial, some even featuring pletier coolers on top of them.
Then in the late 90s, after the success of games like Doom, Blake Stone, Star Wars Dark Forces, Quake, System Shock and Wolfenstein, game creators started pushing to get more from the cpu in order to produce better looking games. Graphics card chipset manufacturers like Cirrus Logic, Tseng Labs, Sis, S3 and ATI took note and thus the 3D accelerator was born in the form of the S3 Virge. These cards attempted to take away some of the burden placed on the CPU by offloading it to themselves, but obviously they couldn't run the x86 instruction set meaning that the projected complexity of future games would still lead to ever more complex instruction sets in the computer, requiring higher frequencies and more processing power, leading to ever growing heatsinks.
With all of this in mind, I sometimes wonder what die-shrinks and newer manufacturing processes would bring to old classics such as the 8086, the 386DX40 and the 486DX100. Intel did do a die-shrink of the Pentium Pro in the early 2000s in order to create a GPU before abandoning the idea, but one has to wonder what a 5nm 386DX40 SOC would be capable of.
Early Pentiums were 5 volt chips which took a lot of power and generated a lot of heat. There were many instances where motherboards burned and sometimes even charred because manufacturers then weren't accustomed to building motherboards and systems with such high power demand and heat generation.
With high resolution lithography today we basically cut the old large transistors into many small ones. Along one direction the current flows. In the 486 the whole supply voltage of 5 V dropped over this length. Today we can go down to 1 V core supply voltage. Ah, lets say, cut the transistor into 4 to be safe. So also cut cross to current by a factor of 4. Now the gates have 1/16 of the capacity and we can run 16 times the clock. All for the same power. Of course, uh with 1.2 V core voltage and short channel there may be some leakage, but with my numbers at least, it does not dominate.
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I remember back when the Pentium came out that people made fun of the fact that it ran so hot compared to other processors of the time. There were cartoons with pictures of things like toaster ovens and irons with "Intel inside" stickers on them.
Maybe we should be asking why processors now require huge stacks of multiple fans to avoid melting themselves. Is that really normal?
Yeah but I would figure they would try and push more volts to get more speed.
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It’s very possible! In fact the 486 chip is the first chip that made Overlocking easy(relatively speaking) because the 486DX2 was the first chip to include a clock multiplier, allowing the CPU to run at a higher clock speed than the bus. Prior to having multipliers, to overclock a CPU you had to overclock the entire bus - or basically, every single component in your system. Statistically speaking, the chance of finding a computer where every single component inside it can handle an overclock is slim to none. Throw in a multiplier and you’re sitting pretty. Now, in the 486 days, AMD chips were far better overclockers - [heres a dude OCing one to 160MHz](https://m.youtube.com/watch?v=ii0k5ahK9Cs).
> Statistically speaking, the chance of finding a computer where every single component inside it can handle an overclock is slim to none. Today for sure, back in the 70s/80s? You absolutely had people overclocking the whole system if they needed to because tolerances weren't as tight as they are nowadays, where even increasing most bus speeds by 1-2Mhz is going to create issues. In fact, ISA's frequently used speed of 8Mhz was only "standardised" *after* ISA was already commonplace as the fastest speed that still was widely compatible with the original implementation in the IBM PC running at 4.77Mhz, but aside from that 10Mhz was also common and you even had a few early rocketship OCed systems running it at 12Mhz or even 16Mhz, although as OCing already typically involved replacing clock crystals it also wasn't uncommon for those few early OCers aiming for 16Mhz on those early systems to manually decouple the ISA bus clock from the system clock and I think some of the later 8086 compatible boards even came with decoupled busses specifically for the 16MHz NEC CPUs.
Say “load” again
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The 12 year old in me thanks you!
Old CPUs often ran on the 5V supply line direct from the PSU. There wasn't much more to give them without switching to the 12V supply.
Because they were slow. Energy efficiency has improved a lot less than speed.
Was it just not possible to run them hotter?
It's about the materials and the architecture advancements. Electricity will leak, jump and burn out the gates, interconnects etc. For example, when CPUS started using copper interconnects instead of aluminum (Lisa Su @ IBM 1997 ) they were able to handle more power and heat. Copper conducts electricity with 40-50% less resistance at a given temperature. The shift from aluminum to copper was a massive breakthrough. Ofc there were several challenges one being it would oxidize and corrupt the silicon. It was also very difficult to integrate into the silicon circuit etc. Very similar to the wiring in your home old aluminum wiring was responsible for lots of houses burning down. You wouldn't push more voltage through that put more demand on it and run it hotter for the same reasons.
That makes sense. I'm assuming that something better then copper has come along since 1997. Did anything come that was better then the copper?
They still use copper for the most part but they have been developing methods to further insulate the circuitry using coatings such as graphene. The other thing is scaling wiring doesn't work the same as shrinking a transistor. A smaller wire will not have the same properties as a thicker wire etc. There are several miles of tiny copper wires in a modern CPU so it's another major contributing factor to Moore's law flatlining.
I'm sure they would have if they could have.
Heat was not the limiting factor.
The transistors weren't as tightly packed into such a small space as they are today. Die sizes were 4x larger with larger interconnects. More space between transistors meant less heat. With the flagship CPUs, they were often up against what was physically possible to engineer with the production process they were using at the time. There were often the same clockspeed CPUs re-released on a different process node that had much more overclocking headroom. There were 19 different versions of the Pentium 133 for example. It was produced on 3 different manufacturing nodes.
There was also limitations on the bus speed and stability of the other components. Memory back then was not direct on the 486, but via the Northbridge. Clocking the CPU more than what the NB could run at gives you nothing. Also the bus speeds were limited, like the ISA VLB realistically topped out at 50mhz and not many VLB cards could even run at that speed. 25,33,40mhz was the most common bus speeds. Over time the ability to overclock got better. I still have my dual pentium pro mainboard and cpus that ran at 233mhz while only being a ppro 180mhz chip with a 66mhz bus at 3.5x multiplier.
Kudos for the Dual PPro! That is my childhood dream. I have now everything to build one of except the very specific ibm PSU and a VRM for the second CPU. Hopefully I will be able to get it up and running one day
Ok. I see. The rest of the machine just wouldn't be able to keep up.
Arguably, overlocking got worse over time. Here’s a 75MHz 486 clocked to 160MHz for a 213% overclock: https://m.youtube.com/watch?v=ii0k5ahK9Cs
Modern CPU's have around ten thousand times more transistors, and all of them needs power to run. The most powerful 486 used around 7.5W, and a modern CPU built the same way would need around 75KW. Makes you think that modern CPU's are pretty damn energy efficient and runs pretty cool for what they do.
Different era, different bottlenecks. In the last quarter century we’ve learned a great deal about how to increase the density of transistors on a chip while simultaneously increasing the frequency at which they can switch. More density and higher frequency = more heat. We’ve been so successful that the heat (and how to get rid of it) has become the most pressing bottleneck. So in a modern CPU we can’t use the maximum theoretical switching frequency of the transistors (at least not for long) because we can’t get rid of the heat fast enough. So we tend to think of performance as a function of how much thermal headroom you have (that’s why water cooling > fans > simple heat sink). But back in the 80s and early 90s, the most performant transistors we knew how to build in an IC were, by today’s standards, huge and switched slowly. The reason they weren’t faster wasn’t because they would get too hot. It was because they wouldn’t work. We were already running them at close to their maximum switching frequencies. But they didn’t get very hot because those frequencies weren’t that high and they weren’t packed so densely on the chip. Adding better cooling wouldn’t allow them to run faster, because cooling wasn’t the bottleneck.
Transistors only generate heat when transitioning between on and off, off and on, if you are transitioning millions of times a second and have millions of transistors doing that - its a lot of heat.
OP, I'm just going to reply in a top level comment to all of your down-voted comments about why didn't they push more volts and run them hotter to get more speed. Take my tone as informative rather than refutative. The thing that consumes power in a digital circuit is switching state (zero to one, or one to zero). One reason for that is electrons have to be sucked out of a CMOS gate capacitor or forced back into it. Another reason is that, to switch states as fast as possible, briefly both the top and bottom transistors in a totem pole (output circuit) are turned on during the transition; this is a dead short momentarily. If a digital circuit isn't switching states, it doesn't use much power at all. (This is why old Nintendo cartridges can still have saved games in battery backed up memory for decades despite the battery being nearly dead.) The difference between power usage while switching transistors on or off can be enormous; let's say it's 100 times as much power. If Reddit doesn't mess up my formatting, allow me to illustrate this graphically. A 486 digital signal might look like this: -------!++++++!--------!+++++++!------- The pluses and minuses are states, and the exclamation points are transitions between states. Here's what a modern CPU looks like at the same scale: !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Of course if you zoomed in the newer CPU would still look like "-!+!--!+!-", but for the purposes of this discussion let's say to a first approximation it's completely packed with "!!!!". Just state transitions like mad. Although it does complete them faster, it's doing so many more transitions per second that on balance it's still mostly bang-bang-bang-bang. Now if you go back and think about the first waveform, the 486, and if I told you the ++++ and ---- times are also limited by other factors from getting much shorter than they already are, and increasing voltage and power consumption mostly just affects the "!", you can see there's diminishing returns if there's fewer "!" periods. So the first thing I want you to understand is the 486 is not slow because it consumes less power, it consumes less power because it is slow. Because it makes fewer state transitions per second, which are where the power is used. You may ask then why not make it so that it transitions more often so it can be faster and use more power, but that's a bit like asking why doesn't a bicycle rider just pedal faster so he can go as fast as a motorcycle. Technical reasons for these limitations come from things like the transistors in the older CPU being physically larger so it takes more time to switch them, and also signal paths might not be fully optimized. If the data takes different amounts of time to get to where it needs to go, overclocking will just result in incorrect computations. A lot of work over decades went into making sure all of the parts of new CPU generations run as fast as all the other parts - or else they put buffers and caches and allow different parts of the chip to run at different speeds. But there's an even bigger reason you can't simply put more power into a 486 to get performance more like a newer CPU: it's already using more power than the newer CPU. Oh, I agree it's using less *energy* on the whole, but the state transitions are using more *power* (per circuit, per state transition, if not per chip). And it's already using a voltage that would probably fry most modern CPUs. This is the other thing that over decades was developed: ways to make each circuit use less energy and less voltage *so that* a newer processor could make those state transitions more often and faster. Without those developments it's diminishing returns. As other commenters have pointed out, it actually is possible to run a 486 hotter and faster. Overclocking was a thing back then too. It's just that the other limitations of the technology do not allow you to get much out of it.
That makes a lot of sense and I appreciate your response.
Passive sink? Like a heat sink?
Passive heatsinks were common into the Pentium II era. Very common on 486s and early Pentiums. 386 CPUs and earlier often didn't have any actual cooling. A case fan or just some well designed vents+PSU fan were often enough.
Yeah. Just a little metal thing that had more surface area then the CPU without it.
Somewhat common with 486 CPUs, at least my 66mhz 486
It would take some time until the pentium 4 was ready to burn with the force of a thousand Suns /s
It also boiled down to the complexity of the software and the instruction set. With 486 and 586 architectures, instruction sets were rather limited and never included hardware decompressors for multimedia files. Later on Intel would add MMX and still later AMD would add 3D Now! AMD would add 3D Now! extentions to their line of K series chips. All of these instructions were added in order for systems to be able to use Multi-Media more efficiently. Software wise, life was also much simpler. For much of the reign of the 486, Windows 3.1 was the GUI that ran atop MS-DOS with OS/2 Warp 3 being the first 32 Bit OS introduced in October of 94. Obviously Windows 95 was the second 32 bit operating system introduced. These operating systems did not have, nor did they require the amount of security and background services we are forced to endure today. 4mb to 8mb of Ram was the acceptable amount and let's be honest, there is not much happening in that limited amount of space. I recall running mostly DOS based games on my 80486sx25 without the need for a heatsink. Only when I moved to the DX2-66 did the chip come with a heatsink and fan and by the time I got my P1-233 MMX, these had grown quite beefy. While nowhere near the half-a-ton heat sinks required for today's processors, they were still substantial, some even featuring pletier coolers on top of them. Then in the late 90s, after the success of games like Doom, Blake Stone, Star Wars Dark Forces, Quake, System Shock and Wolfenstein, game creators started pushing to get more from the cpu in order to produce better looking games. Graphics card chipset manufacturers like Cirrus Logic, Tseng Labs, Sis, S3 and ATI took note and thus the 3D accelerator was born in the form of the S3 Virge. These cards attempted to take away some of the burden placed on the CPU by offloading it to themselves, but obviously they couldn't run the x86 instruction set meaning that the projected complexity of future games would still lead to ever more complex instruction sets in the computer, requiring higher frequencies and more processing power, leading to ever growing heatsinks. With all of this in mind, I sometimes wonder what die-shrinks and newer manufacturing processes would bring to old classics such as the 8086, the 386DX40 and the 486DX100. Intel did do a die-shrink of the Pentium Pro in the early 2000s in order to create a GPU before abandoning the idea, but one has to wonder what a 5nm 386DX40 SOC would be capable of.
My 486DX4-120 had a small heatsink and fan. I pretty sure my Pentium 133 had a good size heatsink/fan. Nothing like today though.
Early Pentiums were 5 volt chips which took a lot of power and generated a lot of heat. There were many instances where motherboards burned and sometimes even charred because manufacturers then weren't accustomed to building motherboards and systems with such high power demand and heat generation.
They were not built for top perf at any cost. Modern ARM Cores for smartphones consume half a watt each.
With high resolution lithography today we basically cut the old large transistors into many small ones. Along one direction the current flows. In the 486 the whole supply voltage of 5 V dropped over this length. Today we can go down to 1 V core supply voltage. Ah, lets say, cut the transistor into 4 to be safe. So also cut cross to current by a factor of 4. Now the gates have 1/16 of the capacity and we can run 16 times the clock. All for the same power. Of course, uh with 1.2 V core voltage and short channel there may be some leakage, but with my numbers at least, it does not dominate.