The motivation for the change is that Intel's making the baseband instead of Qualcomm now, so it's not an ARM/Hexagon like it once was.
The author is just bent around a decade plus out of date view of chip architecture.
Additionally given that this is a very low power low level embedded system device for a specific function it seems most likely that it's also, like Intel's old Atom chips, a refined derivative of older simpler x86 chips with in-order execution, no speculative execution, no µop transforms or other stuff like that. Would be kind of interesting to learn some of the details, but at any rate that means whole classes of security issues people are already bringing up in this thread (like Spectre/Meltdown) are entirely irrelevant. If some arch simply lacks speculative hardware period then that's that. Simplicity in general can have major performance impacts sure, but it's also lower energy and more secure.
PCI-E does DMA, and AFAIU was inspired by Infiniband (another RDMA protocol).
But no, you're not safe because crappy USB drivers can probably be exploited if they're expecting the USB device to be playing nice.
A USB-C/USB3 physical port makes things a bit more complicated, as it also could be attached to a controller supporting Thunderbolt, which is PCIe.
The unsafe part of plugging in a USB device is probably at the OS level rather than the protocol level - in my opinion you're much more likely to be owned by something like connecting a device with a buggy or compromised driver, mounting a filesystem containing an FS exploit, or reading a file containing an application exploit than by a USB-level protocol exploit.
Finding a USB protocol level exploit would be like finding an exploitable bug in how a NIC does scatter/gather of packets. Like, notings impossible, but damn.
You still shouldn't stick random unknown USB devices into your computer though.
Edit:
Guess Intel got the CDMA assets via its purchase of VIA Telecom assets in 2015. Wonder why it’s taken this long to come to market?
Thanks a ton!
Also I'm a bit baffled that they wrote a tool to measure the entropy of the machine code, tried hand-disassembling and considered that it might have been an encrypted binary format before guessing that an Intel chip could be running an Intel CPU. But they did try "EVERY POSSIBLE RISC ARCHITECTURE [they] KNOW" because apparently nobody ever used CISC on embedded devices. Nobody tell him about the GameBoy.
Of course I'm a bit harsh, it's easy to mock in hindsight but it's still not very interesting technically.
moreover, all previous iterations of Intel basebands were custom ARM cores based around Infineon IP acquired by Intel to be competitive in the baseband market...you did not even read my document, because I said this about the old baseband version
moreover, by the nature of baseband itself, it requires a CPU capable of real-time or near real-time processing, as a matter of fact other vendors are using Cortex-R CPU, which is an ARM cpu made for real-time os, giving you predictable timings, especially interrupt processing and memory access
for example, Cortex-R gives you a special kind of memory, called TCM (Tightly-Coupled Memory) memory, which gives you predictable memory access timings, something that you cannot obtain with a simple cache
by the way, Cortex-R is also used in WiFi chipsets, because the type of processing required is very similar (check the excellent writeup done by Google's Project Zero about this)
so yes, it is interesting to see how Intel managed to implement this kind of features in an x86 CPU, which was never designed for such kind of requirements
I suggest you take a look at the References in my document, they might provide some useful information on the matter
of course if you're not interested in baseband reversing, then I guess you're right, it's not technically interesting material
they were Hexagon only just for few models (iPhone 5 and 5s I think), before that, they were using the Infineon baseband, which guess what...it's what Intel bought :)
btw, for the last 10+ basebands were mostly ARMs, with very few exceptions (the already mentioned Hexagon), check also Mediatek and Huawei basebands
and yes, I don't like having an x86 as an embedded CPU, but that's my problem, I guess...