Intel's Haswell Moves Voltage Regulator On-Die 237
MojoKid writes "For the past decade, AMD and Intel have been racing each other to incorporate more components into the CPU die. Memory controllers, integrated GPUs, northbridges, and southbridges have all moved closer to a single package, known as SoCs (system-on-a-chip). Now, with Haswell, Intel is set to integrate another important piece of circuitry. When it launches next month, Haswell will be the first x86 CPU to include an on-die voltage regulator module, or VRM. Haswell incorporates a refined VRM on-die that allows for multiple voltage rails and controls voltage for the CPU, on-die GPU, system I/O, integrated memory controller, as well as several other functions. Intel refers to this as a FIVR (Fully Integrated Voltage Regulator), and it apparently eliminates voltage ripple and is significantly more efficient than your traditional motherboard VRM. Added bonus? It's 1/50th the size."
Update: 05/14 01:22 GMT by U L : Reader AdamHaun comments: "They already have a test chip that they used to power a ~90W Xeon E7330 for four hours while it ran Linpack. ... Voltage ripple is less than 2mV. Peak efficiency per cell looks like ~76% at 8A. They claim hitting 82% would be easy..." and links to a presentation on the integrated VRM (PDF).
Re:Heat (Score:4, Informative)
You're going to run into that heat anyway, whether it's on the motherboard in general or on the CPU. You can't win. But at least it's better to have heat build-up near a heat-sink, so for high-power conditions it might actually be better to put it on the CPU. I'm also an electrical engineer, but thermals are really a mechanical engineer's realm, so I can't run numbers for you.
Re:Heat (Score:5, Informative)
My suspicion(if only for die-space reasons, it isn't purely cosmetic that contemporary VRMs occupy a substantial amount of board space) is that is this a 'marketecture' summary of Intel moving some additional voltage adjustment and power gating functions on die, to support dynamic adjustment of power to the greater number of components(multiple CPU cores, possibly independently clocked, GPU, RAM controller, PCIe root, etc.); but we'll still see a bunch of chunky power silicon under serious heatsinks clustered around the CPU socket.
Given that much of the contemporary power savings are achieved by superior idling, rather than absolute gains in maximum power draw, Intel is either going to have to keep moving power regulation on die, or start dedicating even more pins to tiny voltages at nontrivial currents, with the associated resistive losses; but that won't necessarily change the fact that the circuitry that brings the 12v rail down to what the CPU wants is a pretty big chunk of board.
Full presentation (Score:5, Informative)
You can find the full slide set in PDF format here [psma.com].
If I read this right, it really is a fully on-chip switching regulator, inductors and all. They already have a test chip that they used to power a ~90W Xeon E7330 for four hours while it ran Linpack. (Or a virus -- it says Linpack in the summary page.) Voltage ripple is less than 2mV. Peak efficiency per cell looks like ~76% at 8A. They claim hitting 82% would be easy, and there are "additional advancements that cannot be reported at this time" planned for the future.
The slides have bunch of other technical details about testability features, too, which is always neat to see.
Re:Heat (Score:5, Informative)
Can someone please tell me why this is a good idea
The long story is here (PDF) [psma.com]. Motherboard will still do the heavy lifting from 12V to 2.4V, but the integrated VRM will distribute it. Advantage is extremely clean, fine-grained, low-latency and flexible power supply to deliver exactly as much power to where it's needed and probably - this is just speculation on my part - allowing the CPU to work on a wider range of voltages since there's less noise and ripple so you don't need the same tolerance limits. It sounds perfect for smart phones, tablets and laptops that are primarily battery-limited, nice to have for average machines but potentially an issue for overclockers. All you need is cooling though, it shouldn't limit overclocking if you can keep the temp down.
Re:sinking heat? (Score:5, Informative)
Re:Heat (Score:5, Informative)
Being 1/50th the size it will be welcome on mobile devices. Not sure that its a good thing for your gaming desktop.
That 84 watts is going to rip through your mobile device's battery pretty damn fast.
Re:Heat (Score:2, Informative)
Actually, no real device is ohmic at all. Even a resistor will heat up with increasing current causing an increased resistance that is non-linear. For us EEs, ohmic devices are our massless pullies and frictionless inclines.
Re:Heat (Score:5, Informative)
Ohm's law is completely irrelevant to this situation *in the form you describe*. "Burning a hole through the board" would be possible and a simple function of Ohm's law only if they were using a linear regulator to generate the Vcore. But VRM's have been switching DC/DC converters since the 486 days. They achieve a voltage conversion by switching the incoming voltage on and off *very fast*, which results in an output voltage that's a function of the input voltage and the duty cycle of the on/off switching. An inductor (current-smoothing) and capacitor (voltage smoothing) give a nice clean DC voltage.
The differences between on-motherboard VRMs and this new in-package (it's technically a separate chip...) are significant. First off, physically moving it closer means that you're not sending 100+ Amps of current over the 3-4 centimeters of generally very thin copper traces on the PCB, they're sent millimeters through die-bond wires, or even through a solid substrate (no idea what Intel does at that level). There's your Ohm's law coming into play at that level, but the power losses there are relatively minimal since you're talking maybe a few tenths of an ohm. Die-bond wires are going to drop that to 10's of milli-ohms probably, so nothing major but still a positive effect.
The main reason this will generate a lot less heat is because of the *frequency* of the switching. Because this on-board VRM is so much smaller, it can switch the input faster (shorter wires, less parasitic capacitance, less ringing, etc.). This in turn means smaller value components required, e.g. the switch from the monster inductors seen on the motherboard (at maybe 1-2MHz switching) in the slide to the tiny chip-scale inductors on the FIVR (at 10's or 100's of MHz). The end result of all of this is that switching losses get significantly smaller. It's those losses that create heat local to the regulator. If they can for example go from an 80% efficient VRM to an 90% efficient FIVR for a 100W CPU load, they reduce the switching losses from 25W to 11.1W.
Re:Full presentation (Score:5, Informative)
Re:Heat (Score:5, Informative)
Intel might be the first to do it on a CPU die, but they're not the first to do on-silicon inductors by any stretch. Switching regulators with inductors on silicon have been commercially available for several years now. The R-78 [digikey.com] and MIC33030 [micrel.com], for example, are drop-in replacements for linear regulators, with all components on die.
The real question in my mind is why anyone still uses linear regulators for anything, but I digress.
Re:Heat (Score:2, Informative)
Sorry, but I design quite a lot of switch mode regulators for my own hardware design, and there are several concerns here:
- the efficiency of 76% they claim is abysmally low, my regulators are never below 80% in their operating range, and often above 90%, with peaks in the 96-97% range.
- switch mode regulators need an inductor, and inductors need ferrite or iron cores, which is not going to happen on a silicon die. External inductors are much better
but low loss inductors for large currents are large, for fundamental physical reasons.
- the fastest acheivable switching frequency is in the low tens of MHz, and this is with considerable losses. Lowering the frequency decreases the losses which happen while the swictch(es) change state, which are dominating at higher swictching frequency. At lower switching frequencies, losses are dominated by I2R
in chokes and traces.
- increasing switching frequency allows to increase loop bandwidth and transient response, but another way to improve transient response is to increase output capacitance, which is relatively cheap at low voltage and is best attained by a parallel combination of ceramic capacitors (class II dielectrics like X5R/X7R, never use class III like Z5U or Y5V, they have horrible temperature and voltage dependent characteristics) for high frequency filtering and low ESR tantalum (like
AVX TPS, designed for this task) for absorbing transients while the regulator adapts within the limits of the loop bandwitdh.
- loop bandwidth can never be much above one tenth of the switching frequency, to avoid excessive phase shifting due to the sampling that makes the loop unstable
- an efficient way of minimizing ripples is to have several regulators in parallel with the same clock phase shifted. I've got exceptionnally low ripple in this case
(could not measure it with a good scope, not with a voltmeter whose bandwidth included the switching frequency).
- for the large currents, the regulator will be dierctly connected to a ground plane and to an output voltage plane, voltage drops on plane should be low enough
if you put enough vias to the component (BGA/LGA), and you can always sense the voltage back from the largest consumer.
Re:Heat (Score:3, Informative)
I do SoCs with integrated regulators now.
Their inductors are on-chip using extra thick metal levels. But "extra thick" levels on sub-20nm chips are still pretty damn thin, meaning high r/square, so the Q they can get out of the inductors is pretty low, especially since the configuration they use (linear coupling rather spiral) will also limit their available Q. That's what's driving their efficiencies down from what you're used to in discrete buck regulators.
The big advantage of integrating this is that you don't get the all the nasties of the pads. You usually get the power routed to the corner pins on an SoC and a big chip can easily generate 20+ nH and 1 pF on the pins of a wirebond SoC, and even a flip-chip will still see more than 10 nH typically. That's a problem when trying to deal with power transients, so the on-chip regulator really helps get the ripple down since it can sense/adapt to the voltage at the pin.
Personally, the big eye-opener to me was doing 400A of DC power on chip. Even at sub-1V the electromigration issues they have must be killer.