Hi Thomas, On Sun, Mar 28, 2021 at 03:07:24AM +0200, Thomas Gleixner wrote: > On Sun, Mar 28 2021 at 00:25, Willy Tarreau wrote: > > On Sat, Mar 27, 2021 at 10:13:22PM +0100, Mateusz Jonczyk wrote: > > FWIW I tested on my ASUS 1025C which runs on an Atom N2600 forced to > > 32-bit. I had already tried in the past but wanted to give it a try > > again in case I'd have missed anything. Sadly it didn't work, I'm > > still getting the "requires an x86-64 CPU" message. > > > > Given these machines were really cheap, I've always suspected that they > > employ cheaper, low-grade CPUs, possibly having been subject to reduced > > tests where x86_64-specific parts were not even verified and might be > > defective. This may explain why they forcefully disable long mode there, > > but that's just speculation. > > There are some of these '32bit only' CPUs out there in the wild which > actually support long mode. Some of them even do not have the long mode > CPUID bit fused out.
Yes, I'm aware of this as well. We might even have talked to the same "victim" :-) > But whether it works is a different story: > > - If the CPUID bit is on, then the chance is high, but it runs out of > spec (guarantee wise) > > - If it's off is still might work by some definition of work as they > might have fused off more or there are actual defects in some 64bit > only area which are irrelevant when in 32bit mode. > > Even if it could work perfectly fine, the BIOS/SMM/ucode can prevent > switching to long mode. > > It's a lost cause. I agree. While I bought this netbook to have a 64-bit CPU and was extremely disappointed, after seeing that it was not just a matter of "oops we forgot to enable LM", I concluded that it was pointless to try to go further, as I would never trust it anyway. Cheers, Willy
