You are not logged in.

#1 2016-10-17 08:20:44

Raize
Member
Registered: 2016-06-24
Posts: 10

Early Microcodes, SSE4, Xeon Mods...

I recently did the S775-S771 mod to allow me to fit a Xeon X5450 in my socket 775 P35 motherboard.

After updating the BIOS to the latest version, the processor does work, but when I run lscpu there is no sse4_1 flag, which I think may be reducing performance.

I installed the intel-ucode package and configured GRUB to do an early microcode update in the hopes that this would enable the sse4_1 without having to modify my BIOS, and the microcode update is happening:

[    0.000000] microcode: microcode updated early to revision 0xa0b, date = 2010-09-28
[    0.650078] microcode: CPU0 sig=0x1067a, pf=0x40, revision=0xa0b
[    0.650083] microcode: CPU1 sig=0x1067a, pf=0x40, revision=0xa0b
[    0.650090] microcode: CPU2 sig=0x1067a, pf=0x40, revision=0xa0b
[    0.650098] microcode: CPU3 sig=0x1067a, pf=0x40, revision=0xa0b

These are definitely the correct and latest microcodes, but there is still no sse4_1 flag when I run lscpu. I really don't want to modify the BIOS to add the microcodes, and to be honest, I don't see why it would make any difference whether the microcodes are loaded by the BIOS or during boot.

Can anyone help me get SSE4 working?

Offline

#2 2016-10-17 10:51:29

frostschutz
Member
Registered: 2013-11-15
Posts: 1,409

Re: Early Microcodes, SSE4, Xeon Mods...

I don't see why it would make any difference whether the microcodes are loaded by the BIOS or during boot.

The running system (or glibc really) can't handle changes in CPU flags. This is a problem with Haswell in particular... if you don't use early microcode with Haswell the system will crash (better to not use any microcode at all, than late microcode).

In your case the bios is probably responsible. You are using an unsupported CPU (wow) after all, I'd be glad it works at all.

There have been cases of bioses not providing all available cpu flags before... some laptops with AES-NI cpus hid the aes flag from the OS. Not sure how this works but apparently bios has some say in these things.

Offline

#3 2016-10-18 04:18:16

Raize
Member
Registered: 2016-06-24
Posts: 10

Re: Early Microcodes, SSE4, Xeon Mods...

frostschutz wrote:

The running system (or glibc really) can't handle changes in CPU flags. This is a problem with Haswell in particular... if you don't use early microcode with Haswell the system will crash (better to not use any microcode at all, than late microcode).

OK, good to know.
I modified the BIOS and re-flashed it and now I am getting all the right cpu flags. Although sadly it is not benchmarking any better.

Offline

Board footer

Powered by FluxBB