I have no idea really, but technically, x86-based phones don't need to have any legacy hardware at all. Namely, the two common phone-OSes that run on x86 are Windows Phone and Android, and both were developed for ARM, which doesn't have any PC legacy at all.
So an x86-based phone wouldn't need to have any either.
On the other hand, earlier Atom-based systems ran on 'standard' desktop chipsets. So it could be that even the SoCs of today have the legacy hardware built in. I doubt that's enough to actually boot a legacy OS though. You can't boot legacy OSes on modern PCs very well either, because you won't have the proper drivers for SATA, PCI-e, USB etc. So basically it's the non-legacy stuff that causes the problems.

Modern x86 tablets, and likely phones, all are UEFI boot only. They don't have any BIOS compatibility module at all.

NJRoadfan wrote:

Modern x86 tablets, and likely phones, all are UEFI boot only. They don't have any BIOS compatibility module at all.

No, but I thought the question was about the hardware (does it support the usual 8237s, 8253, 8259s etc).
Because if they do, I suppose it wouldn't be that difficult to get an UEFI-to-legacy BIOS shim working.

Those chinese tablets that can run Windows 7 are probably compatible, but x86 Windows Phone / Android devices? One would need to investigate further, but I doubt it. The vídeo card doesn't really need to have VGA compatibility, stuff like the PC speaker and PS/2 ports do not exist, the disks do not need to be accessed through an ATA interface and I really doubt the manufacturers would keep unneeded hardware compatibility if dropping them would lower the costs of the device.

alexanrs wrote:

I really doubt the manufacturers would keep unneeded hardware compatibility if dropping them would lower the costs of the device.

I think this somewhat depends on the markets where these chips are sold.
For example, at my previous company, we used AMD Geode and Intel Atom-based systems, which had to run a fullblown Linux distro, so they had to be fully PC-compatible, and they were.
I can imagine that there is some demand even for (Free)DOS-compatible x86 SoCs (I know Canon cameras used to be built around a 186-compatible processor, running ROMDOS). So it could be that it's more economical for Intel to keep some of that legacy around, than to cut a few transitors and lose out on those sales...

My Bay Trail Atom Z tablet doesn't have BCM in its firmware at all. Heck, people had problems getting 64-bit Linux distros along with Windows 7 working on them since they only supported 32-bit UEFI despite having 64-bit CPUs. Prior to Windows 8, it was assumed that PCs were going to be 64-bit UEFI only until Microsoft pulled a fast one.

Necroposting a bit, but hey.

Basically, the smartphone Atoms (Z34xx/Z35xx for 22 nm, the x3 line for 28 nm budget chips) are x86 CPUs, but neither of them are PC-compatible in any way. They do have VT-x, so you can run Windows in a VM (because the VM emulates all of the I/O), but they can't run anything PC-compatible on the metal, because they have none of the PC legacy I/O, it's all modern smartphone I/O - this includes desktop Windows. You'd need a different HAL to do that, and that's not happening.

The tablet Atoms (Z36xx/Z37xx for 22 nm, the x5 and x7 lines for 14 nm) are PC compatible at the hardware level, though - they still have an internal ISA bus, they have PCI/PCIe internally (although it's not bonded out to the package, so you can't plug a PCIe card into a system using these chips), etc., etc. (IIRC, the 14 nm ones don't have A20 gate emulation, though, Intel's finally dropping that, but everything else is both XT and AT compatible at the hardware level.) However, as mentioned before, they don't usually have a CSM, meaning that only OSes that work with UEFI will boot - no DOS for you. There's nothing technically preventing this, though, and a company could absolutely release a firmware that offers legacy boot for these chips.

Also, IIRC, the next generation of Atoms (still 14 nm, but with a new CPU design) are going to unify the smartphone and tablet parts, so the new smartphone chips will regain XT and AT compatibility at the hardware level.