Flaws In Intel Processors Quietly Patched

Nom du Keyboard writes "According to this article in The Inquirer and this Microsoft Knowledge Base article, a fix for some significant problems in many of Intel's most recent processors has been quietly released — by whom is not clear. Patches are available on Microsoft's site. Affected processors include Core 2 Duo E4000/E6000, Core 2 Quad Q6600, Core 2 Xtreme X6800, XC6700, and XC6800. Details on just what has been fixed are scanty (it's called a 'reliability update'), however, it's probably more important than either Intel or Microsoft is openly admitting." There is no indication that Apple users are affected.

Comments

Microcode

[bblount]

This patch affects the microcode, which are the underlying machine instructions: http://en.wikipedia.org/wiki/Microcode

How could this not affect Intel Macs? They use the same machine instructions that everyone else does!

Some more details

[macemoneta]

I had submitted some additional details in a rejected submission:

Two months ago, Intel introduced microcode updates for all systems with an Intel® Core(TM) 2 Duo processor. According to an HP Tech Support Document:

While the implications of the issue are difficult to quantify, any of the following symptoms can occur:

* The system may stop responding to keyboard or mouse input.
* A system operating in a Microsoft Windows environment may generate a blue screen.
* A system operating in a Linux environment may generate a kernel panic.

This was the first I had heard of this; probably a good time to check for BIOS or microcode updates."

The HP link also indicates the nature of the problem, which should not be OS specific:

This Intel microcode update addresses an improper Translation Lookaside Buffer (TLB) invalidation that may result in unpredictable system behavior such as system hangs or incorrect data.

Re:Ugh, I hated that bug.

[Wavicle]

Oh did you?

1) The Pentium FDIV bug produced an incorrect answer in 1 in 9 billion double precision floating point divides. It did not affect integer divides.
2) The answer always contained at least 14 correct significant bits (usually more, but an error in the 15th significant bit was the worst case). The means that single precision calculations were almost invariably correct.
3) Any hack to solve the problem would have been hundreds of times slower than just living with a small error in so few calculations.
4) All games today get by just fine using single precision floats for rendering.
5) It took a guy (Thomas Nicely) with a Ph.D. doing heavy research in computational number theory to find it, yet you found it while working on a game in QuickBasic.

I think Nicely said it best in his FDIV flaw FAQ:

Bear in mind, however, that the likelihood is 1000 to 1000000 times
greater that any erroneous results obtained on a Pentium are due to
software errors, rather than any error in the CPU.

and also:

Over a period of five years, no person was ever able to collect a
reward offered for exhibiting (other than with a code artificially
contrived to demonstrate the error), on either of two workplace
systems intentionally left with flawed CPUs installed, an error
caused by the flaw.

Re:correct

[ocbwilg]

The Linux kernel is not currently affected, though some multi-processor apps with homegrown assembly might be.

The problem is some sort of atomic operation sequence. Somebody let slip a reference to the bug on a mailing list today, without any real details. Probably the details are still under NDA.

I did some digging around, and it actually looks like this is a patch for a bug in the Translation Lookaside Buffer (TLB) that was discovered back in April. Microsoft has released a patch for people running current versions of Windows (Vista, XP, and server 2003) but if you're running anything else then you will have to get a new BIOS update to resolve the issue. If you check the major hardware vendors web sites (HP, IBM, etc) the are offering patches to their system ROMs regardless of the OS.

I know that it's popular on Slashdot to claim that Linux isn't vulnerable to the same bugs that Microsoft operating systems are, but when it comes to processor bugs (errata, in Intel-speak) that's simply not the case. Linux does make use of the TLBs. Every modern OS does. If you look at the hardware vendors' web sites, you will see that they specifically state that the bug could lead to a BSOD on Windows or a kernel panic on Linux.