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UEFI boot x86 machine on x64 cpu

uefi x86 on x64 cpu

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#1 brajomobil

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Posted 21 January 2015 - 09:57 AM

Like the topic say is it possible ?

 

The tablet only has EFI no legacy mode bios, and it has x64 cpu.

 

I have tried booting with VHD x86 , also no luck...



#2 steve6375

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Posted 21 January 2015 - 10:09 AM

Some tablets have a 64-bit CPU but are 32-bit UEFI.

It would help if you stated what tablet it is, and what you want to boot.



#3 brajomobil

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Posted 21 January 2015 - 10:13 AM

Hi,

It is teclast x80h , with intel Intel Bay Trail-T Z3735F.

Win 8.1 x86 

 

Thanks in advance.



#4 steve6375

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Posted 21 January 2015 - 10:18 AM

So why not make a bootable USB stick using Rufus from a Windows install ISO and try it?

 

a 32-bit UEFI system needs to see a \EFI\boot\bootia32.efi file - it MUST be present on the USB stick and should be on a FAT32 partition.

 

Your system may be 64-bit UEFI, in which case you should use a 64-bit Windows Install ISO to make the bootable USB drive with and check that a \EFI\boot\bootx64.efi file is present on the USB drive.



#5 brajomobil

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Posted 21 January 2015 - 10:31 AM

Is that USB with Rufus the same like this:

 

Created USB with win8.1 x64 instalation. Instaled it with UEFI. everything OK.

Then applied install.wim from win8.1 x86 instalation on GPT partition where win8.1 x64 was installed.

 

Boot starts but error: 0xc0000359

 

Tried various bcd repair stuff, nothing helped.



#6 steve6375

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Posted 21 January 2015 - 10:39 AM

So you have a 64-bit UEFI system, but want to install a 32-bit UEFI OS?

Is that correct?



#7 brajomobil

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Posted 21 January 2015 - 10:41 AM

Yes, but it does not need to be uefi x86. Any thing that will boot x86 machne from x64 uefi 



#8 steve6375

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Posted 21 January 2015 - 10:49 AM

When you say 'x86' -  do you mean Intel CPU-based system or  Intel x86 32-bit machine??

I am confused because x86 just means Intel CPU instruction set - you can have x86 32-bit CPUs or x86 64-bit CPUs?

 

If you successfully installed Windows 64-bit OS via UEFI, then you have a 64-bit UEFI system.

Therefore it has to boot to using 64-bit UEFI files written in 64-bit long mode.

if your system has no CSM support, then I think you can only boot from 64-bit long mode efi files??



#9 brajomobil

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Posted 21 January 2015 - 11:00 AM

I mean 32bit machine. Booted by uefi x64.

 

Tablet does not have CSM legacy boot and that is the problem...



#10 brajomobil

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Posted 21 January 2015 - 11:36 AM

Can we some how patch "bootx64.efi"   to start/load  "bootia32.efi" ?



#11 steve6375

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Posted 21 January 2015 - 11:43 AM

I don't know - maybe others do?

What's wrong with  64-bit Windows? Is it too large and you are trying to save space? In that case there are ways to save space  - e.g. use wimboot and install using WinNTSetup?



#12 brajomobil

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Posted 21 January 2015 - 11:47 AM

Nothing wrong with 64 bit. The problem is in specific drivers for external usb device, only 32bit

and it will remain like that for unknown time :(



#13 steve6375

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Posted 21 January 2015 - 12:25 PM

I see. So no 64-bit driver for any Windows OS is available?

Maybe others have suggestions...



#14 brajomobil

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Posted 21 January 2015 - 12:26 PM

Yes, no 64 bit drivers at all. Only 32 bit.


Edited by brajomobil, 21 January 2015 - 12:47 PM.


#15 Tripredacus

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Posted 21 January 2015 - 04:47 PM

Windows 8+ 32bit (and by extension, its WinPE counterparts) support booting in UEFI mode.

Regarding this:

Some tablets have a 64-bit CPU but are 32-bit UEFI.


Can I find information on this? It is my understanding from the UEFI 2.3.1 spec that all UEFI is 64bit. From real-world use, I have found some manufacturers have firmware to limit reporting of a CPUs capabilities to 32bit or 64bit OS use only. I can't post a link right now as MSFN is down.

#16 steve6375

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Posted 21 January 2015 - 04:54 PM

A 64-bit CPU can run in 64-bit long mode or 32-bit long mode. Some tablets/netbooks choose to have a 32-bit UEFI 'BIOS' so it can (presumably) use the smaller payload OS of Windows 32-bit.

see http://rmprepusb.blo...-using-e2b.html and Asus T100.



#17 brajomobil

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Posted 23 January 2015 - 11:53 AM

Reading various forums this is the conclusion:

Without another version of "bios" with UEFI x32 bit it will not be possible.

 

Also I have found another tablet that has UEFI x32 bit but no UEFI x64.

teclast x98 air.

 

No tablet with both options of "bios" :(

 

Thank you all for the help and time to share...

 

Best rgerads,

brajomobil


Edited by brajomobil, 23 January 2015 - 11:55 AM.





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