Author Topic: Why have CPU's stopped at ~1.8 GHz?  (Read 15301 times)

0 Members and 1 Guest are viewing this topic.

Offline brucehoult

  • Super Contributor
  • ***
  • Posts: 1735
  • Country: nz
  • Formerly SiFive, Samsung R&D
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #50 on: May 30, 2017, 03:27:42 pm »
I would also add that current processors already operate at an energy density roughly equal to the surface of the sun

Hmm.

Skylake-K is according to Anandtech 122.4 m^2, which means with a 95W TDP that's 775 kW/m^2. Wiki says the Sun's luminosity is 3.828e26 W, and surface area is 6.09e18 m^2, so 62.8 MW/m^2.

So the Skylake energy density is almost two orders of magnitude lower.

Still, it's a lot.

Thus you see graphics cards with essentially 1000 Z80 processors on board

I don't think anything would be remotely like a Z80. At least the ones I'm familiar with are more like 1000 Cortex M4F processors, but with far more registers (and therefore longer instructions to encode them), but with maybe eight CPU cores sharing one program counter and instruction decode logic, and also operating as a "barrel processor" running maybe four threads in sequence (also processing the same instruction).
 

Offline Ampera

  • Super Contributor
  • ***
  • Posts: 2567
  • Country: us
    • Ampera's Forums
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #51 on: May 30, 2017, 04:04:14 pm »
Even though AMD is back into the performance game, Intel has a DAMN sight more money than AMD, and if they feel threatened they could steamroll AMD (no pun intended) within a year.
Professional complainer-in-chief criticizing other people's code
Programmer and bumbling Unix fool
Op @ EEVBlog IRC: irc.austnet.irc #eevblog
 

Online T3sl4co1l

  • Super Contributor
  • ***
  • Posts: 15875
  • Country: us
  • Expert, Analog Electronics, PCB Layout, EMC
    • Seven Transistor Labs
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #52 on: May 30, 2017, 04:12:48 pm »
AFAIK, GPUs are more about wide data than oodles of [independent] cores.  That is, you have, say, a thousand ALUs, and registers and pipelines and all that, but they're all driven by the same instructions from the same decoder and program counter.

Probably, they use a few levels of this approach, so it's not that the whole chip is doing just one series of instructions in lockstep, but a few in parallel, each of which is controlling a lot of parallel computations.

But I haven't done anything with them personally, so take this for what it is...

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Online wraper

  • Supporter
  • ****
  • Posts: 12157
  • Country: lv
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #53 on: May 30, 2017, 05:14:37 pm »
DDR5 has passed 7GHz speeds already.
Nope, divide that by 4 and get a real frequency.
 

Offline Muxr

  • Super Contributor
  • ***
  • Posts: 1347
  • Country: us
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #54 on: May 30, 2017, 05:34:21 pm »
DDR5 has passed 7GHz speeds already.
Nope, divide that by 4 and get a real frequency.
Yup. It's a bit annoying when manufacturers count data rate as frequency.
« Last Edit: May 30, 2017, 05:36:05 pm by Muxr »
 

Online james_s

  • Super Contributor
  • ***
  • Posts: 12613
  • Country: us
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #55 on: May 30, 2017, 07:06:29 pm »
It would be interesting to see what one could do with 1,000 Z80s, probably best tried in a large FPGA than using actual Z80 chips.
 

Offline grumpydoc

  • Super Contributor
  • ***
  • Posts: 2751
  • Country: gb
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #56 on: May 30, 2017, 08:03:02 pm »
It would be interesting to see what one could do with 1,000 Z80s, probably best tried in a large FPGA than using actual Z80 chips.
Not all that much

Modern processors are, conservatively 10's of 1000's of times faster than the Z80

Just on clock speed the fastest Z80 was 20MHz (the later, more highly integrated Z80181 and the EZ80's did go a bit faster) - modern CPU's are 3-4Ghz so there is a factor of 200 right there, 1000x if you compare a 4MHz Z80.

But we can factor roughly 6x more for the fact that it takes a Z80 about that many clocks on average to execute an instruction and at least 4x for working in 8 bit chunks not 32 - eg for a 32-bit memory to memory add (i.e operands in RAM, result to RAM) takes a Z80 about 80 clocks compared with 4 on an i386 so there's a 20x speed-up there. That brings us to 4000x before we consider more complex operations (how long does a 32-bit multiply take on a Z80?), super-scalar execution, 64 bit ops, SIMD/Vector ops, FPUs that can do 80 bit floating point operations in one clock and multiple cores per die. Oh and the miserly amount of RAM that a Z80 can address compared with a modern CPU.

1000 Z80's is worth maybe 5% tops of a core i7.

Edit2: OK, in an FPGA you could clock them a lot faster than "real" Z80s but even then......

It's still my favourite 8-bit micro though (6809 gets close however).

EDIT: changed 32-but multiply to 32-bit multiply. A 32 but multiply is what my teenage son does when doing his maths homework. :)
« Last Edit: May 30, 2017, 08:23:32 pm by grumpydoc »
 

Offline Ampera

  • Super Contributor
  • ***
  • Posts: 2567
  • Country: us
    • Ampera's Forums
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #57 on: May 30, 2017, 08:21:17 pm »
TBH, my favorite micro is the 32-bit M68000. The register arrangement pleases me, and it's incredibly easy to program for with every instruction you could need in a basic CPU. That being said I have never really programmed much with it, but that's more out of being lazy than anything else.

The Z80 is a neat CPU, but it's IPC ratio is pretty poor compared to other micros of the time (Like the 6502)

Probably my least favourite has got to be the PPC. I first off do not like reduced instruction set CPUs, but to make matters worse, the execution by AIM was terrible. They did, granted, use IBM's POWER CPU which in it's own right is not a bad chip. Even still I don't hate the PPC and it found a lot of use in Macs for years, and even the 6th, 7th, and 8th generations of video game consoles all saw at least one PPC console. Even today, the PPC line is still used by the Amiga.
Professional complainer-in-chief criticizing other people's code
Programmer and bumbling Unix fool
Op @ EEVBlog IRC: irc.austnet.irc #eevblog
 

Online james_s

  • Super Contributor
  • ***
  • Posts: 12613
  • Country: us
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #58 on: May 30, 2017, 10:27:36 pm »
My favorite classic CPU is the 6502, partly because it was used in so many great systems and partly because it's such a great example of inexpensive minimalist hardware that people figured out all sorts of clever ways to make it do amazing things. It's the core of quite a few arcade games from the golden ere, it was used in the Commodore 64, the original Nintendo (in modified form) and countless other iconic systems of the late 70s through the mid 80s.
 

Offline grumpydoc

  • Super Contributor
  • ***
  • Posts: 2751
  • Country: gb
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #59 on: May 30, 2017, 10:29:31 pm »
TBH, my favorite micro is the 32-bit M68000. The register arrangement pleases me, and it's incredibly easy to program for with every instruction you could need in a basic CPU. That being said I have never really programmed much with it, but that's more out of being lazy than anything else.
+1

Quote
The Z80 is a neat CPU, but it's IPC ratio is pretty poor compared to other micros of the time (Like the 6502)
Maybe, the Z80 just needed more clocks to step through its internal state machine but I'm not sure it mattered much.

The 6502 can execute some instructions in one clock cycle whereas the Z80 takes 4 clocks to do the simple stuff and more to do anything complex. But the 6502 is hampered by its lack of registers, reliance on page zero and lack of any 16-bit operations - so in practice most instructions are at least two bytes/cycles.

So, whereas it looks at first sight that a 1MHz 6502 ought to be as fast as a 4MHz Z80 in practice the ratio was closer to 1:2 with a 4MHz Z80 having a slight edge on a 2MHz 6502 - when these were the fastest parts available that gave Zilog the edge. Also the Z80 moved on to higher clock speeds (eventually 20MHz for the CMOS part) whereas I don't think the 6502 got past 3MHz.

You can still buy new Z80's from mainstream distributors - I don't think that's true for the 6502.
 

Online james_s

  • Super Contributor
  • ***
  • Posts: 12613
  • Country: us
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #60 on: May 30, 2017, 11:45:33 pm »
The 6502 is still in production and available from mainstream distributors, clock speed up to at least 14 MHz but IIRC there are faster ones available.

http://www.mouser.com/ProductDetail/Western-Design-Center-WDC/W65C02S6TPG-14/?qs=sGAEpiMZZMtVFuKNr6IGvpdkwXR9vVB1
 

Offline Ampera

  • Super Contributor
  • ***
  • Posts: 2567
  • Country: us
    • Ampera's Forums
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #61 on: May 31, 2017, 12:23:51 am »
TBH, my favorite micro is the 32-bit M68000. The register arrangement pleases me, and it's incredibly easy to program for with every instruction you could need in a basic CPU. That being said I have never really programmed much with it, but that's more out of being lazy than anything else.
+1

Quote
The Z80 is a neat CPU, but it's IPC ratio is pretty poor compared to other micros of the time (Like the 6502)
Maybe, the Z80 just needed more clocks to step through its internal state machine but I'm not sure it mattered much.

The 6502 can execute some instructions in one clock cycle whereas the Z80 takes 4 clocks to do the simple stuff and more to do anything complex. But the 6502 is hampered by its lack of registers, reliance on page zero and lack of any 16-bit operations - so in practice most instructions are at least two bytes/cycles.

So, whereas it looks at first sight that a 1MHz 6502 ought to be as fast as a 4MHz Z80 in practice the ratio was closer to 1:2 with a 4MHz Z80 having a slight edge on a 2MHz 6502 - when these were the fastest parts available that gave Zilog the edge. Also the Z80 moved on to higher clock speeds (eventually 20MHz for the CMOS part) whereas I don't think the 6502 got past 3MHz.

You can still buy new Z80's from mainstream distributors - I don't think that's true for the 6502.

Fair enough. Maybe poor wasn't the right word, but you still need a higher clock to get things done.


I will also punch the next person who calls a 68k a 16 bit CPU. If you call a 68k a 16 bit CPU you also have to call the 8088 an 8 bit CPU, and the P5 Pentiums 64 bit.

And for those who play video games, the Genesis is 16 bit only if the SNES is 8 bit.
Professional complainer-in-chief criticizing other people's code
Programmer and bumbling Unix fool
Op @ EEVBlog IRC: irc.austnet.irc #eevblog
 

Offline technix

  • Super Contributor
  • ***
  • Posts: 3321
  • Country: cn
  • From Shanghai With Love
    • My Untitled Blog
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #62 on: May 31, 2017, 12:38:08 am »
Just remember that the declared clock speed of a processor is the speed of the external clock only.   They routinely divide that clock a lot before it reaches the ALU.   Different parts of the CPU operate at sometimes vastly different clock speeds internally.

That was true in the 70s and early 80s. It hasn't been true since around the 80486/68040 era, and certainly not since anything Pentium/PowerPC. Except for the dog called Pentium 4, where they bumped the MHz for marketing reasons, but it wasn't really real.

Indeed clocks these days are multiplied up for internal use.

Well, yes, the external 100 MHz or 133 MHz or whatever clock is multiplied by 30 or 35 or 40 or 45 to get the internal (and advertised) clock speed, and it's even adjusted dynamically for power consumption, temperature, or load reasons.

Even microcontrollers now have clock frequency multipliers. For example STM32F407ZGT6 can take an 8MHz crystal and generate a 168MHz clock out of it (8MHz / 8 * 336 / 2 = 168MHz.) this stands true for 8-bit cores too like ATtiny85 (8MHz * 8 / 4 = 16MHz) or PIC16F1455 (16MHz * 3 = 48MHz)
 

Offline Alex Eisenhut

  • Super Contributor
  • ***
  • Posts: 2371
  • Country: ca
  • If you can buy it for 4$ on eBay, why design it?*
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #63 on: May 31, 2017, 12:46:02 am »
*Except AC/DC adapters on eBay. Avoid them all!
 

Offline Nusa

  • Super Contributor
  • ***
  • Posts: 1875
  • Country: us
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #64 on: May 31, 2017, 12:52:07 am »
68000 was a bit of a hybrid, bitwise. 32-bit internal bus, but 16-bit data bus.

The Sega CD had TWO 68000's and a Z80. How many bits is that? I developed games for it in the early 90's. The dev system's been sitting in a box since then. Might still work, but it was tempermental even when I was actively using it. Had to leave it powered up 24/7 to avoid random lockups.
 

Offline Ampera

  • Super Contributor
  • ***
  • Posts: 2567
  • Country: us
    • Ampera's Forums
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #65 on: May 31, 2017, 01:25:43 am »
That's pretty cool. TBH I am actually interested in that. I don't have really any money at the moment, but in the future, would you be willing to sell it?

And yes, the 68k was a hybrid, but at it's heart, it had a 32-bit instruction set, internal data bus, and registers. The only 16 bit part to it was the data bus and ALU. Addressing was 24 bit.
« Last Edit: May 31, 2017, 01:29:40 am by TwoOfFive »
Professional complainer-in-chief criticizing other people's code
Programmer and bumbling Unix fool
Op @ EEVBlog IRC: irc.austnet.irc #eevblog
 

Offline Carl_Smith

  • Frequent Contributor
  • **
  • Posts: 259
  • Country: us
    • MegaMicroWatt - Carl Smith's Blog
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #66 on: May 31, 2017, 02:29:25 am »
It would be interesting to see what one could do with 1,000 Z80s, probably best tried in a large FPGA than using actual Z80 chips.

For years I've wanted to build a board with a crap ton of whatever is the cheapest 8 pin micro.  Like 1000 of them on a board.  Hook them all together somehow so they can work on some massive parallel processing application.   Could hook one output pin into an input of the next chip and have a 1000 step pipeline of tiny PICs or AVRs.  Or I could wire up a grid that could load some data across a row then step it down through the columns.

Thing is, it's a solution I don't have a problem for.  So I never did it.  And I know the Core i7 in my laptop would run circles around it.   But I still think about doing it...

« Last Edit: June 01, 2017, 04:56:00 am by Carl_Smith »
 

Offline Alex Eisenhut

  • Super Contributor
  • ***
  • Posts: 2371
  • Country: ca
  • If you can buy it for 4$ on eBay, why design it?*
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #67 on: May 31, 2017, 02:32:00 am »
Sounds like a bit slice processor?

https://en.wikipedia.org/wiki/Bit_slicing
*Except AC/DC adapters on eBay. Avoid them all!
 

Offline TiN

  • Super Contributor
  • ***
  • Posts: 4199
  • Country: us
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #68 on: May 31, 2017, 04:26:15 am »
I've overclocked Intel Celeron (Netburst arch) to 8.2GHz about 10 years ago :).
Yes, that is with liquid nitrogen (-196c) cooling.  Intel Core i7 2600K CPUs were very common to do 4.9-5GHz 24/7/365 with decent cooling.
Yesterday released Core i7-7xxx X-series have clocks over 4GHz even for 10-core CPU. So yea, 1.8GHz was actual around 15 year ago with Athlon XP and Intel P4 era.
YouTube | Metrology IRC Chat room | Live-cam | Share T&M documentation? Upload! No MB limit, firmwares, photos.
 

Offline grumpydoc

  • Super Contributor
  • ***
  • Posts: 2751
  • Country: gb
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #69 on: May 31, 2017, 07:04:08 am »
The 6502 is still in production and available from mainstream distributors, clock speed up to at least 14 MHz but IIRC there are faster ones available.

http://www.mouser.com/ProductDetail/Western-Design-Center-WDC/W65C02S6TPG-14/?qs=sGAEpiMZZMtVFuKNr6IGvpdkwXR9vVB1

Ah, I stand corrected :)

I wonder what uses those. There again I wonder what uses new Z80s
 

Offline coppice

  • Super Contributor
  • ***
  • Posts: 5944
  • Country: gb
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #70 on: May 31, 2017, 08:46:32 am »
The 6502 is still in production and available from mainstream distributors, clock speed up to at least 14 MHz but IIRC there are faster ones available.

http://www.mouser.com/ProductDetail/Western-Design-Center-WDC/W65C02S6TPG-14/?qs=sGAEpiMZZMtVFuKNr6IGvpdkwXR9vVB1

Ah, I stand corrected :)

I wonder what uses those. There again I wonder what uses new Z80s
I don't know who uses the 6502, but it seems an entire organisation is kept alive by it, since http://www.westerndesigncenter.com/wdc/ seems to handle nothing else.

The Z80 core is inside numerous things. I doubt many use the traditional 40 pin DIP Z80 now, but quite a few still use the core, sometimes running at hundreds of MHz.
 

Offline Ampera

  • Super Contributor
  • ***
  • Posts: 2567
  • Country: us
    • Ampera's Forums
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #71 on: May 31, 2017, 04:52:16 pm »
It's used in the 100+ USD Ti-83 and 84 line of calculators. I will never buy a single thing from Ti, and for as long as I can I will not touch one. Ti is ripping off hundreds of thousands, maybe even millions of college students. A group of people who are normally gutted for cash. 100+ dollars for a 1 dollar Z80 computer, 25 cent display, 10 penny keyboard, and couple cent case. It's highway robbery.

If you are in the market for a calculator, buy HP. They do a hell of a lot more than Ti, and for the same price. My HP Prime cost around 110 USD, and is 3 times as fast as even the most powerful Ti calculator on the market.
Professional complainer-in-chief criticizing other people's code
Programmer and bumbling Unix fool
Op @ EEVBlog IRC: irc.austnet.irc #eevblog
 

Online james_s

  • Super Contributor
  • ***
  • Posts: 12613
  • Country: us
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #72 on: May 31, 2017, 05:52:44 pm »
I'd bet it costs a lot more than you estimate to build those TI calculators. They may be overpriced but not to the degree you suggest.

You want an example of highway robbery just look at textbooks. They make trivial revisions consisting mostly of shuffling things around and call it a new edition which you then have to buy at exorbitant cost. Your expensive book is then almost worthless once a new edition comes out.
 

Offline Syntax_Error

  • Regular Contributor
  • *
  • Posts: 204
  • Country: us
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #73 on: May 31, 2017, 05:55:50 pm »
It's used in the 100+ USD Ti-83 and 84 line of calculators. I will never buy a single thing from Ti, and for as long as I can I will not touch one. Ti is ripping off hundreds of thousands, maybe even millions of college students. A group of people who are normally gutted for cash. 100+ dollars for a 1 dollar Z80 computer, 25 cent display, 10 penny keyboard, and couple cent case. It's highway robbery.

If you are in the market for a calculator, buy HP. They do a hell of a lot more than Ti, and for the same price. My HP Prime cost around 110 USD, and is 3 times as fast as even the most powerful Ti calculator on the market.

 ::)

Ah, yes. All hail the almighty college student, the noblest of all demographics, entitled to free and cheap...everything. Again,  ::)
« Last Edit: May 31, 2017, 05:58:14 pm by Syntax_Error »
It's perfectly acceptable to not know something in the short term. To continue to not know over the long term is just laziness.
 

Offline edavid

  • Super Contributor
  • ***
  • Posts: 3012
  • Country: us
Re: Why have CPU's stopped at ~1.8 GHz?
« Reply #74 on: May 31, 2017, 06:15:17 pm »
68000 was a bit of a hybrid, bitwise. 32-bit internal bus, but 16-bit data bus.

That is not really correct, the 68000 had a 16 bit ALU and internal data bus.  This is obvious from the instruction timings, and has been confirmed by die photos.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf