Thanks for that, but i've seen in a couple of places that this doesn't fix the problem, and may make matters worse.

The real problem is that for reasons unknkown and totally illogical Dell no longer wish to support users who want S3 sleep, and so don't have that support in their BIOS.

I'm perfectly happy to go buy HP, Asus, whatever if they support S3, and I wondered if anyone else was exploring this.

@Charles_xps13 
Whats up, I just bought a xps 7590 to replace my older xps m1530 and one of the only problems I have with it is the sleep issue your experiencing. Machine is perfect except for it! I searched for a few hours looking to resolve it and came across this post on the forum and the registry edit here completely solved the sleep issue on my machine and I haven't had any issue with it since! Hopefully it works for you, I am using the latest BIOS, 1.5 I think. 

https://www.dell.com/community/XPS/Dell-XPS-15-9570-not-going-to-sleep/td-p/6206588

Hope it helps you!!

OK thanks for all the replies.

I did try this, and it seems to work in a fashion, but the only way to wake up now is a long press of the power button. A short press (as with my HP laptop) seems to wake something up, but the display remains blank.

With all my previous laptops (HPx3, Toshiba) A long press on the power button is usually associated with a forced power down.

The problem is caused by the Dell BIOS; Dell has totally ignored user requests for S3 sleep support.

I'll just go back to how it was before, and delete Dell from my shopping list.

> The problem is caused by the Dell BIOS; Dell has totally ignored user requests for S3 sleep support.

I don't think its the BIOS, per se; S3 sleep works perfectly in Linux on my 7390 2-in-1.

Thing is, Micro$oft believes that Sleep time is too precious for them to let laptops sleep soundly, even if their owners would prefer so. M$ demands all new laptops that support S0 to default to S0, and they don't support switching from S0 to S3 after Windows has been installed (this has been reported to often work via a registry hack, but sometimes fails). Hence, for legit S3 these days, BIOS must deny that S0 is supported, which should be provided as a BIOS option by laptop makers. It is not enough to support S3. Of course, going Linux is an alternative. 

Dell presumably don't like the burden of supporting two sleep modes, for both of which bugs do get reported, and are difficult to diagnose.  

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@Charles_xps13 wrote:

Dell XPS-9370 

That one thing is the lack of S3 sleep mode and Dell buying in to Microsoft's ludicrous "connected standby"

 

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Not sure if this helps, but on my Alienware Aurora-R6 desktop, I had a similar situation.

In the BIOS:
Disabled - Intel Ready Mode Tech
Enabled - DeepSleep Control in S4 and S5
Enabled - USB Wake Support in S3 (Can now wake from Sleep with Mouse)

In Windows:
- Uninstalled the Intel Ready Mode Technology program.

Machine now Sleeps nicely, but will still wake for Scheduled Windows Events (like Macrium Reflect backups). 

Were you able to solve this? I'm so frustrated I could throw the bloody DELL from the window(s)! To troubleshoot such idiotic nonsense at the evening, after the whole day of meetings/troubleshootings, it's completely perverse! As I wrote in another thread: this is my last DELL machine. Not having sleep in 2020?!?!?! I will sell this brick and switch to HP really, am googling it right now filled with frustration.

I also have the same issue.
I want to conserve power, because it's a 6 core 45 watt chip in the 7590.
When you're on battery mode, you want the chip to not boost so high, so I enabled throttlestop to apply the disable turbo, which keeps it to 2.6.(but that's less ideal as it seems to prevent it form under-clocking)
But when I sleep the machine, either by closing the lid, or by pressing the power button, or even 5 minutes standby, it goes into some pseudo-sleep mode, which is not sleep at all, but simply logged out with the screen off.
Dell must enable the option to disable S0 in bios, there's so many other extra bios features in there that other laptops don't include, why not include one that will be truly useful?
If I shut the laptop lid, I want the CPU to be OFF, and the screen OFF, not fans spinning and 90c temps as soon as you lift the lid, what kind of primitive **bleep** is that, anyway?
If microsoft wants to enable a constantly connected spy program, Dell should refuse this because they have a 45 watt chip not a 7 watt snapdragon or whatever it is.
97watt-hour battery is huge, with a little bios tweaking, improved sleep, and an option to adjust turn-on-off turbo, boosting and disable a few cores, should be also inside the Dell software in windows 10.
That way you're engineering your device to actually give a **bleep** about battery life.
Right now, the 6 core 45 watt boosts over 4ghz on battery, with no option to sleep.
Unlike the previous user I'm not going to sell this laptop, but it's just another failure on laptop manufacturers to make a perfect device - which isn't hard, all you have to do is listen to customer complaints and enable the fix, but there's likely too many men in suits without the ability to have the rank in their corporation to pull the trigger, and just a bunch of bald psycho yes men squandering the profits of the corp.

In the meantime I'm going to keep trying to registry edit the thing until I can disable s0 and have s3 by default.
I also experience some freezes for less than 1 second in games, despite the frames being very high.
Who knows how to diagnose such a thing? Very difficult, i'd have to reinstall windows as a first try to fix.

HI! Any solutions yet?

I have the same problem with my XPS 7590. But it worked before. Don't know what happened, but it no longer works.

I also tried to set the registry key " \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power" to 0 but no improvement.