> FWIU, USB 3 is faster than FireWire

You've missed the point. The title of the article reads "The tragedy of FireWire" - how a good standard was victimized due to corporate politics. FireWire was 10 years ahead of USB. In 2002, FireWire 800 provided a data rate of 800 Mbps, full-duplex. On the other hand, USB 2 only had 480 Mbps, half-duplex. USB didn't catch up until 2010, after USB 3.0 was released. FireWire uses 30 V, 1.5 A power, and it supports power delivery up to 45 watts. USB didn't offer anything similar, not even the latest USB 3, until 2014 after Power Delivery and Type-C's standardization - and real applications only started to ramp up by ~2017. Both limitations of USB 2 were detrimental to some applications, e.g. using hard drives on a PC was painful due to speed and power constraints, had FireWire became more common, it would not be an issue. FireWire can also do everything Ethernet can do (in fact, 1394b's signaling is better than 100Base-TX Ethernet, and has lower radiation), networking is natively supported, you can network two computers together directly with a 1394 cable! On USB, it's only possible using an external controller. One application was NAS, a hard drive can be shared directly over 1394, and mounted as a local drive. Not possible with USB. Finally, 1394b does not have USB's 5-meter limitation due to protocol timing, and natively supports signaling over CAT-5 and fiber optics cable for a distance of ~50-100 meters - on USB, it requires a media converter running vendor-specific custom protocols and not interoperable. All of these features are standardized in 2004 in IEEE 1394b.

Of course, limitations are not inherently USB 2's failures, they have different applications, FireWire was more expensive, and USB's goal was low-cost. But the tragedy was that bad business decision prevented FireWire to achieve its full potential, slowly fading out, and eventually became irrelevant after USB 3 despite its initial good engineering.

FireWire was a tragedy.

> Due to DMA (Direct Memory Access) in most implementations, IEEE 1394 ("FireWire") can be used to directly read from and write to RAM.

This is why we need IOMMU.

You should not blame IEEE 1394 for DMA attacks just because it supports DMA. I agree that the tragedy of FireWire probably prevented a common PC exploit vector as an lucky unintentional consequence, but it's just a symptom, not the actual issue - and the symptom has came back in another form.

Most sufficiently fast hardware interfaces support DMA, and they're equally vulnerable - this includes PCI-E, ExpressCard (which exposes PCI-E), USB 4 (which exposes PCI-E port), Thunderbolt (which exposes PCI-E). Practical exploits are already widespread, not limited to arbitrary memory reads/writes, but also OptionROM arbitrary code execution if a Thunderbolt device is plugged in at boot time.

And this is not only a problem for external ports like 1394, USB 4 or Thunderbolt. Threats also exist from internal devices, like a Ethernet or Wi-Fi controller on the motherboard. While you cannot initiate a DMA transaction via Ethernet (without RDMA) or Wi-Fi since they don't expose PCI-E, the fact that those are connected directly to PCI-E implies any vulnerability in the controller firmware potentially allows an attacker to launch a DMA attack. Exploits already exist for Wi-Fi controllers.

This is the real problem. While the mechanism of IOMMU exists, CPU manufacturers and operating systems previously did little to systematically protect the system from DMA. In the past, Intel intentionally removed IOMMU functionality from low-end CPUs and motherboard chipsets in order to sell more Xeon CPUs to enterprise users. Also, while IOMMU is supported by operating systems, kernel code and drivers were not systematic audited for security - serious IOMMU bypass vulnerabilities have been previously discovered (and patched) in macOS and Linux's IOMMU implementations.

With continued proliferation of USB 4 and Thunderbolt, the lack of IOMMU and buggy driver implementation will become a bigger problem.

So far, QubesOS is most most protected operating system from DMA attacks. Untrusted hardware are assigned to a dedicated VM, and IOMMU is enforced by the hypervisor, not the individual device drivers in operating systems. Compromising a device driver in an untrusted domain does not directly expose the rest of QubesOS to attackers.

> and USB implementations do not use DMA.

USB 4 does now.