Ryzen CPU bug crashes PCs using Firewire devices — old school interface causes new school problems on Linux PCs, but a fix is on the way

(Image credit: AMD)

A Linux patch is on the way to solve crashing issues when attempting to use Firewire devices on PCs running Ryzen CPUs and Linux (via Phoronix). The unlikely hardware combination has enough Linux users to get attention from the community, and even a fix coming out with Linux 6.7 will be backported to prior Linux kernel releases.

Firewire, or IEEE 1394, is a data interface designed in the 1980s and most commonly found on Apple Mac computers and digital video cameras. It had many advantages over USB, which came out a decade later but ultimately failed to gain much attraction outside the audio-video market. Steve Jobs pronounced Firewire dead in 2008, and Thunderbolt practically replaced it in 2011.

Despite all that, Linux developer Takashi Sakamoto has pledged to keep Firewire support on Linux alive until 2029. Sakamoto is already making good on his promise with his latest patch, which solves an issue that uniquely affected PCs running AMD Ryzen CPUs. It would seem incredibly unlikely that anyone would be combining two pieces of hardware with nearly a decade between them, but those people certainly exist. They reported an unusually high amount of crashes.

Without getting too technical, Firewire and Ryzen users would often see their PCs crash if the "isochronous cycle timer" register on the CPU was accessed. This register would be accessed if a user ever plugged in a Firewire device or was using software that required constant access to the register.

To fix the bug, Sakamoto's patch doesn't allow access to the register, preventing crashing and time-aware software from being used. In that sense, it's not a complete fix but more of a workaround. This patch will arrive in Linux 6.7 (which launches tomorrow) and will be retroactively applied to older kernels that are still maintained and supported.

Although crashes are no longer a problem for Firewire-Ryzen PCs, the patch is a double-edged sword and "brings apparent disadvantage since time-aware application programs require it," according to Sakamoto. Linux users with this hardware combination might have to switch to Intel or even downgrade to one of AMD's pre-Ryzen CPUs, as neither exhibit the same problems seen on Ryzen-powered PCs.

Matthew Connatser

Matthew Connatser is a freelancing writer for Tom's Hardware US. He writes articles about CPUs, GPUs, SSDs, and computers in general.

  • scottscholzpdx
    I haven't seen a device with a firewire port in nearly a decade. Does this apply to firewire-usb adapters?
  • waltc3
    Thanks for bringing this up--stuff takes me way back! FireWire is ancient, how I remember it well (not really--I used to know why I liked it--but I forgot all that long ago!) I had several iterations of it, though, in my first Windows/OS2 boxes alongside several Amigas back in the late 80's early 90's (not in the Amigas, of course). Got rid of FireWire long before Jobs "declared it dead", though...;) I had USB long before Jobs got the bright idea to use the Intel standard in a Mac (poor Mac users thought Jobs had developed USB, which illustrated well how far behind Jobs actually was), but it's always amusing to see those who think Jobs was this sort of savvy guru when the fact was he was always playing catch-up in one way or another. Don't get me started, please, but I lost respect for Apple/Jobs several decades back. Not surprised that they had to transition to cell phones to make it--and, oh, look! We're not in the "post-PC era" at all, are we?. ...;) Jobs made the RDF (Reality Distortion Field) legendary. Sorry if I inadvertently pummeled someone's sacred cow--it's really not worth arguing.
  • rluker5
    Some motherboards still have PS/2 ports.
  • usertests
    rluker5 said:
    Some motherboards still have PS/2 ports.
    And they aren't going away:
    However, as of 2023, although PS/2 ports are rarely included in off the shelf computer systems, they continue to be included on some computer motherboards and are favored by some users for various reasons including the following:
    PS/2 ports may be favored for security reasons in a corporate environment as they allow USB ports to be totally disabled, preventing the connection of any USB removable disks and malicious USB devices.
    The PS/2 interface provides no restriction on key rollover, although USB keyboards have no such restriction either, unless operated in BOOT mode, which is the exception.
    To free USB ports for other uses like removable USB devices.
    Some USB keyboards may not be able to operate the BIOS on certain motherboards due to driver issues or lack of support. The PS/2 interface has near-universal compatibility with BIOS.Latency of miceUSB mice send data more quickly than PS/2 mice because standard USB mice are polled at a default rate of 125 hertz while standard PS/2 mice send interrupts at a default rate of 100 Hz when they have data to send to the computer. However, PS/2 mice and keyboards are favored by many gamers because they essentially have zero latency through the port. There is no "polling" needed by the OS. The device notifies the OS when it's time to receive a packet of data from it.
  • ollie802
    You'd be amazed how many industrial devices/cameras use old interfaces like this.
  • Neilbob
    rluker5 said:
    Some motherboards still have PS/2 ports.
    I was utterly devastated when my ancient PS/2 keyboard finally bit the dust. It was so fantastically heavy and robust it could serve multiple purposes: satisfyingly noisy typing, walloping intruders over the head or, if a bunch were obtained, paving Rome.

    As for Firewire, that was never quite so ubiquitous. I can't imagine the number of people affected by this is particularly large.
  • prtskg
    Admin said:
    A strange Linux bug would crash the system for Ryzen CPU owners that use Firewire devices.

    Ryzen CPU bug crashes PCs using Firewire devices — old school interface causes new school problems on Linux PCs, but a fix is on the way : Read more
    From the phoronix article-
    "VIA VT6306/6307/6308 provides PCI interface compliant to 1394 OHCI. When the hardware is combined with Asmedia ASM1083/1085 PCIe-to-PCI bus bridge, it appears that accesses to its 'Isochronous Cycle Timer' register..."
    Doesn't sound like Ryzen CPU bug, more like combo of VIA and Asmedia is causing problems.