Lowering FSB Increases WPA2 Speed

[Tiesto]

When i lower my FSB i get more kh/s ( From 160 kh/s to 262 kh/s ) In WPA2

has anyone herd of this and is this a real speed increase?

This only happens when i lower FSB using ASROCK OC Tuner and not from windows BIOS.

My max speed with my GPU before was only 160 kh/s (WPA2)

The lowest stable FSB i can achive withought windows crashing is 215

motherboard G41M-VS3 ASROCK
W8.1
R9 280X OC
Hashcat v1.31.64 (Windows)

[epixoip]

Literally impossible. WPA kernel in oclHashcat is ~ 14000000 instructions. You haven't posted your clock speed, so I am assuming a stock 1000 Mhz core clock. 2048 cores * 1000000000 Hz / 14000000 instructions =~ 146.3 KH/s max theoretical performance on a 7970 / R9 280X. Most users benchmark real-world performance around 127-135 KH/s.

So what's going on? Well, I think I have a wild theory that also explains why your hack doesn't work when setting FSB speed in the BIOS.

There seems to be a direct correlation between the FSB speed and the system clock. The system clock is calibrated at boot time using the APIC timer, and the local APIC frequency is dependent upon the FSB speed. So accurate timing depends on the FSB frequency. If the FSB changes on a running system, this has a direct impact on timer accuracy, which affects the system clock.

By using a software utility to adjust the FSB speed on a running system, you are literally slowing the clock down. Therefore 50 seconds of running time in your screen shot likely isn't actually 50 seconds, but more like 1m40s. Because of this Hashcat thinks you are doing twice the amount of work you are really doing.

The reason setting it in the BIOS doesn't work is because the system timer is calibrated at boot time, so it is able to compensate for the lower FSB at boot.

So no, you're not really making Hashcat go any faster. You're just making it think it's gone faster by making your system run in slow motion.

[epixoip]

I'll also further go on to state that there is absolutely no correlation between FSB speed and GPU speed. The GPU is a separate device that runs independent of the host system, only sharing the PCI-e bus, and PCI-e runs off the southbridge not the northbridge. Further, modern day systems (anything made in the last 11 years from AMD / 7 years for Intel) use a NUMA architecture and don't even have a front-side bus, CPUs communicate directly with RAM and do not go through the northbridge for CPU-RAM communication. So no matter how you spin it, it doesn't pass a simple logic test.

[Rolf]

Windows bug probably, as lowering clocks can never provide speed boost by design.
So no, the speed isn't real.
It's either skipping passwords or showing you higher-than-actual speed.

[Tiesto]

There seems to be a direct correlation between the FSB speed and the system clock. The system clock is calibrated at boot time using the APIC timer, and the local APIC frequency is dependent upon the FSB speed. So accurate timing depends on the FSB frequency. If the FSB changes on a running system, this has a direct impact on timer accuracy, which affects the system clock.

My APIC is disabled in bios or whaterver its called, but that does make sense about the FSB adjusting clock time. My fsb is 333 mhz default btw my overclock cpu speed is 3.ghz but on my lower power profile only 1.6 or smthn then clock down to 215 FSb about 1400 mhz.

Literally impossible. WPA kernel in oclHashcat is ~ 14000000 instructions. You haven't posted your clock speed, so I am assuming a stock 1000 Mhz core clock. 2048 cores * 1000000000 Hz / 14000000 instructions =~ 146.3 KH/s max theoretical performance on a 7970 / R9 280X. Most users benchmark real-world performance around 127-135 KH/s.

I can achive speeds of 160 kh/s on my R9280X OC (Overclock edition) default clock is 1100 mhz. It does 160 kh/s right out the box. My settings is 260 acell & 4096 GPU Loops.

Windows bug probably, as lowering clocks can never provide speed boost by design.
So no, the speed isn't real.
It's either skipping passwords or showing you higher-than-actual speed.

Well I hope its not skipping passwords only showing higher speed, I took a note of all the letters that was completed using the lower clocks so i could do them again if need be.

I did however notice that a letter that says would be completed in 4 hours actually took 8, but then other letters actually did take the time it says it would.. I guess this is a bug afterall.

[epixoip]

My APIC is disabled in bios or whaterver its called

I think you are confusing ACPI for APIC. Same letters, different things.

I can achive speeds of 160 kh/s on my R9280X OC (Overclock edition) default clock is 1100 mhz. It does 160 kh/s right out the box.

Well yes, of course if you are overclocking you will get higher speeds. That's why in the math I said I assumed a 1Ghz clock. For 1.1 Ghz,

2048 * 1100000000 / 14000000 = 160.9 KH/s max theoretical performance

So that aligns perfectly what what you are getting.