With the mobile world, people have come to expect instant-on, always connected devices. First it was smartphones, and then tablets based off of mobile operating systems which offered the ability to have the device in a deep sleep state, but still able to connect out to various services for notifications and app events.

With Windows 8, Microsoft brought this same always-on model to devices running Windows. It was a big change from the traditional ACPI Sleep states of S3 (Sleep) and S4 (Hibernate) which power down most of the system. Initially Connected Standby was only available on ARM based devices, but shortly after the launch of Windows 8 in October 2012, Clover Trail based tablets began to emerge which also supported this new sleep state. Connected Standby provides one big change over the traditional sleep and hibernate modes – it keeps networking devices powered on in a low power mode and allows apps and services to run in a restrained mode in order to run background tasks and process push notifications.

Clover Trail was a 32 bit CPU, so it wasn’t surprising that Connected Standby was limited to 32 bit installs of Windows, but since that launch a lot has happened in the x86 CPU landscape. First came Haswell, with a better efficiency than Ivy Bridge which it replaced, but more importantly for the tablet market, Bay Trail was launched. This was a big step up in performance for the Atom line, and Bay Trail is a 64 bit CPU. All tablets launched with Bay Trail came with a 32 bit install of Windows to enable Connected Standby. The 64 bit support was not there for any platform – Haswell or Bay Trail – and it has been a reason to hold tablets back with the 32 bit version of Windows.

In order to support Connected Standby, the entire system needs to be developed with the support in mind, as the following system requirements must be met:

Connected Standby System Requirements
  Requirements Motivation Responsibility
ACPI Flag The system ACPI firmware must set the ACPI_S0_LOW_POWER_IDLE FADT flag. Indicates the platform hardware supports the low-power idle mode for Connected Standby. System firmware developer
Core silicon / SoC must be capable of low-power idle.
ACPI namespace The system ACPI firmware must not provide an S3 object in the root of the namespace. Windows supports a platform that exposes either the S3 object or the ACPI_S0_LOW_POWER_IDLE FADT flag, but not both at the same time. System firmware developer
SoC The core silicon or SoC manufacturer must provide a Power Engine Plug-in (PEP). The PEP coordinates device state and processor idle state dependencies. A minimal PEP is required to communicate to Windows when the device power state dependencies have been achieved for the lowest SoC idle power mode. Core silicon / SoC provider
Windows 8.1 includes the PEP for Intel-based platforms.
Hibernate x86/x64-based Connected Standby PCs must also support Hibernate. Hibernate is used to save the state of desktop / Win32 applications when critical-low battery capacity is reached. System firmware developer
Network Stack All Built-In Networking Devices must be compatible with NDIS 6.3, specifically WoL Patterns, Protocol Offloads, and D0 Packet Coalescing. Enables the SoC to enter low-power modes while the networking device maintains connectivity. System designer (OEM/ODM)
Storage The primary storage volume must be solid-state and have a 0-millisecond seek penalty. Ensures that Windows can safely access the storage device any time during Connected Standby. System designer (OEM/ODM)

Today, we can confirm that Connected Standby is now available in 64 bit installs of Windows 8.1. Anand has confirmed that it is working in the new Surface Pro 3, and Intel has also confirmed to us that the drivers and firmware are complete to allow Connected Standby on Bay Trail-T processors. There has been some questions about the lack of support with some tablets such as the Lenovo ThinkPad 10 now offering a 64 bit install option, but assuming Lenovo has added all of the required pieces for Connected Standby, it should be available. The final result is still dependent on the OEM to choose the correct pieces, and ensure all necessary flags are set. Intel has confirmed that the HP ElitePad 1000 G2 is running Bay Trail-T x64 and has Connected Standby enabled.

With these developments, Intel based tablets can now offer the instant-on capabilities of smartphones, even with the 64 bit OS. AMD currently has no plans to support Connected Standby.

Source: Intel, Microsoft

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  • eddman - Wednesday, May 21, 2014 - link

    Off-topic: Will you ever update the comment system and add an edit feature? Come on.

    You are correct about the rest though, S3 and hybrid, but IMO connected standby easily replaces those.
  • Klug4Pres - Wednesday, May 21, 2014 - link

    Thanks, I missed that in the table, and I had based my observations on a Microsoft tech blog, so this may be a new requirement, or else I misinterpreted what I read, or ...

    I suppose if the hibernate function works reliably from within Connected Standby, to rescue a machine that is running out of juice, this would indeed mostly eliminate the need for the other options, but options are always nice to have.
  • edwpang - Wednesday, May 21, 2014 - link

    Definitely, I can setup my Asus Win8 Tablet to hibernate when battery drops below certain percentage. I can even force hibernation using command script, but I cannot enable the hibernation option in shut down menu on it.
  • javier_machuk - Wednesday, May 21, 2014 - link

    I agree with you, i own an asus t100 tablet and sometimes the battery drains quickly when in connected standby mode. This happened after i downloaded a few third party apps and configured them to receive updates when in standby. Since i figured this out i limited the apps running in standby to only 2, both of them from microsoft and the problem is almost solved(there are still sometimes when it drains the battery).
  • KonradK - Wednesday, May 21, 2014 - link

    Is S4 distinguishable by hardware from a simple power off? As far I know I can hibernate a system, then unplug a power cord, plug it again and then launch computer and successfully unhibernate the system, or boot from diferent drive.
    For me a S4 is more a feature of a system than actual power state of hardware.
  • eddman - Wednesday, May 21, 2014 - link

    S1,S2,etc. are the names of different power states and all fall under the G1 state. They are not exact hardware features.

    For example, a PC that is completely turned off and unplugged is considered to be in the G3 power state.

    Read this for further information:
  • eddman - Wednesday, May 21, 2014 - link

    Ok, maybe I got it wrong.

    Yes, you are right. They are the power states of the whole system.

    Since the system, when hibernated, saves everything to HDD/SSD and doesn't need any power to sustain itself, you can unplug it.

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