21 de agosto de 2009

PCI Wireless Card Realtek 8185 weak signal

The default module to PCI Wireless Card Realtek 8185 has weak signal, something between 5% to 15%, on Ubuntu 9.04 kernel 2.6.28 .

On Mandriva this network device work very well, don't need to worry !

Nevertheless we can solve this problem installing the modeule from Realtek to this device.

The steps are easy:

  1. Download driver from Realtek .
  2. Unzip the file .
  3. Inside the file do make and make install, then reboot
  4. This is a very dirt step, you must install libssl-dev. Try a cable connection to Internet.
  5. unzip wpa_supplicant-0.5.5.zip
  6. cp defconfig .config
  7. make and cp wpa_cli wpa_supplicant /usr/local/bin
  8. reboot and let the job for the networkmanager

5 de agosto de 2009

Benchmark - cpus

Simple benchmark, just floating point calculations.
This can be use to evaluate the performance on Monte Carlo application and numerical recursions without memory use.
We calculate the time for 10^9 m=tanh(ran2(&seed)*m), m=sin(ran2(&seed)*m) and if(ran2(&seed)). (seed=234)
Used cpus in decreasing performance order :

Intel(R) Core(TM) i5 CPU 750 @ 2.67GHz
AMD Phenom(tm) II X4 945 Processor @ 3GHz
Intel(R) Xeon(R) CPU X5550 @ 2.67GHz
AMD Athlon(tm) 64 X2 Dual Core Processor 4000+ @ 2.1GHz
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz - Chipset ICH10
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz - Chipset ICH7

Intel(R) Core(TM)2 Quad CPU Q9300 @ 2.50GHz - Chipset ICH9
Mobile AMD Sempron(tm) Processor 3500+ @1.8 GHz
Intel(R) Core 2(TM) CPU T7200@ 2.0Ghz

Below graph (incomplete) shows time versus cpu for the if(ran2(&seed)) routine
Also the complete spreadsheet