(UEFI) Dell XPS 15z L511z modded BIOS - and HOWTO

[jkbuha]

Hmmm good points:

1) Why would modifying the SSDT's in the BIOS change the voltage - I mean I've done this in OSX at runtime but the voltages still remain the same (I think, though I've never actually measured them in OSX, not sure if you can though - as they have to be reported through SMC?)

2) Good point re: AndyP. I'll drop him a PM.

[TimeWalker]

You've done what at runtime? You are using DropOemSSDT to drop original OEM tables and GenerateCStates to use something slice has hardcoded into his generator which never ever change. I'm not even sure where you are getting you P-States from, probably from predefined plist in PlatformPlugin ??? Not a particularly good idea if you ask me. Besides <key>DsdtName</key> has a default value of <string>DSDT.aml</string>, so there's little to no pint in duplicating this.

AFAIK you can get this reported from IntelCPUMontor, we don't have real SMC and never will, even though our ITE chip is technically an SMSC chip..

I've dropped a post on MDL forum already, not sure how close he's reading his thread though. I've already posted about versions after 2.07 going bananas about firmware volume header missing, but it's still present as of 2.13.

[Stalix]

could someone please explain why there isnt an a12 modded bios with undervolted gt550m vbios? I read through 10 pages and cant figure out why they are not available since before there were older modded bios with gt550m bios? i read its some sort of incompatibility? if so could i please get someone to tell me what is the incompatibility?

and maybe could someone make an a12 bios with undervolted 550m vbios for me to try if its safe?

thank you.

[jkbuha]

You've done what at runtime? You are using DropOemSSDT to drop original OEM tables and GenerateCStates to use something slice has hardcoded into his generator which never ever change. I'm not even sure where you are getting you P-States from, probably from predefined plist in PlatformPlugin ??? Not a particularly good idea if you ask me. Besides <key>DsdtName</key> has a default value of <string>DSDT.aml</string>, so there's little to no pint in duplicating this.

Ah the joys of typing a reply via mobile...

Sorry I was brief - what I was trying to explain (badly) is that I had originally used a modified SSDT table, together with manual P-states and voltages (before I modded the speedstep module), but I'm not sure if it was possible to reduce the voltages by loading this up through chameleon/clover. Why would patching the SSDT in the bios module make any difference - does the CPU take its voltage and P-state references from the SSDT tables?

IntelCPUMonitor only reports clockspeed (and temp), not voltage - maybe I'm missing a trick here?

---

could someone please explain why there isnt an a12 modded bios with undervolted gt550m vbios? I read through 10 pages and cant figure out why they are not available since before there were older modded bios with gt550m bios? i read its some sort of incompatibility? if so could i please get someone to tell me what is the incompatibility?

and maybe could someone make an a12 bios with undervolted 550m vbios for me to try if its safe?

thank you.

It's because I haven't made one (yet). This topic is mainly dedicated to showing everyone how to make their own flavours of bioses, as opposed to making every single one. As long as you can make a recovery bios, you're free to experiment with making your own.

Hope this helps!

[TimeWalker]

Ah the joys of typing a reply via mobile...

Sorry I was brief - what I was trying to explain (badly) is that I had originally used a modified SSDT table, together with manual P-states and voltages (before I modded the speedstep module), but I'm not sure if it was possible to reduce the voltages by loading this up through chameleon/clover. Why would patching the SSDT in the bios module make any difference - does the CPU take its voltage and P-state references from the SSDT tables?

IntelCPUMonitor only reports clockspeed (and temp), not voltage - maybe I'm missing a trick here?

Totally with you on the "typing from a phone" issue.. besides the autocorrect gives me nightmares that's why i've opted for a 7" screen now.

It must be possible as I see people over at applelife are discussing how to reduce voltage by implementing proper ACPI methods for PWM. The thing is, SSDTs are somewhat dynamic when it comes to multiple CPUs, so if at a given time you decide to upgrade your CPU it would change multipliers, power consumption etc, so tables would have to be rewritten again... otherwise BIOS will just generate new stock one according to the algorithm hardcoded into the modules related to power management.

By altering _PSS, not so much _CST, it's possible to change the voltage (or should I say power) CPU draws at a given state. Dell uses SPSS on our machines, the table is Cpu0Ist. Here's an example for my i3:

Code:

Name (SPSS, Package (0x07)
        {
            Package (0x06)
            {
                0x000008FC,
                0x000088B8,
                0x0000006E,
                0x0000000A,
                0x00000083,
                0x00000000
            },

            Package (0x06)
            {
                0x00000708,
                0x000064A6,
                0x0000006E,
                0x0000000A,
                0x00000183,
                0x00000001
            },

            Package (0x06)
            {
                0x00000640,
                0x000056F9,
                0x0000006E,
                0x0000000A,
                0x00000283,
                0x00000002
            },

            Package (0x06)
            {
                0x00000578,
                0x000049D8,
                0x0000006E,
                0x0000000A,
                0x00000383,
                0x00000003
            },

            Package (0x06)
            {
                0x000004B0,
                0x00003E7C,
                0x0000006E,
                0x0000000A,
                0x00000483,
                0x00000004
            },

            Package (0x06)
            {
                0x000003E8,
                0x0000326B,
                0x0000006E,
                0x0000000A,
                0x00000583,
                0x00000005
            },

            Package (0x06)
            {
                0x00000320,
                0x000026E4,
                0x0000006E,
                0x0000000A,
                0x00000683,
                0x00000006
            }
        })

Less power = less heat dissipation = less frequent fan noise = profit.

Newer version of IntelCPUMonitor is able to pickup the voltage on CPU (from kozlek's branch I believe).

[jkbuha]

Oh dear. I've just found a new reason to play about with bios modding again...

Ok I'll try to monitor voltages using HWINFO64 in Win8. In the meantime, do you know offhand the name of the module for the SSDT? Also - are the SSDT-1, -2, -3 -4 stored in a different location?

[TimeWalker]

It will have different GUID on your laptop, at least that's what I've seen when comparing @kasar's modules to mine. All PmRef cpu tables will be in one single modules, DSDT and HPET, UEFI etc will be in another module, nVidia Optimus will be in another module and PTID will be another module. So generally speaking, PWM-related stuff has its own dedicated module.

[jkbuha]

So how do I find it? I mean - is there a specific hex search I can use to trawl through the modules?

[TimeWalker]

Plain simple - it's a freeform module, the header will have PmRef string.

[HairyCube]

jkbuha, you can monitor voltages and even power consumption of the CPU with ThrottleStop: http://i.imgur.com/mgRI718.png
Works nicely with my i7-2620M, should work without an issue on your system as well.