Reader How Tos: Build a PC for TV

The System Is Installed And I Am Ready To Turn On The Power!

It looks like everything is fine. I am now setting up different BIOS settings. CPU FrontSideBus = 533 MHz, and memory is 5:4 speed compared to the FSB. 533 MHz/ 4 = 133*5:4*2 = 333 MHz = DDR 333. Didn’t get this ? My P4 has a quad pumped FSB of 133 MHz, giving you equal to 533 MHz. The memory has a 166 MHz double pumped bus, giving you equal to 333 MHz (DDR333). This means the 133 MHz CPU FSB has to be multiplied by 5:4 to get 166 MHz, and then by 2 because of the double pumped DDR bus.

The memory also must run in CAS 2.0 mode to get the best performance. Further, I enabled the "Smart fan" feature, allowing the system to throttle the system/ CPU fan according to a specified CPU temperature. My P4 has a maximum junction temperature of 70 degrees centigrade. I recommend you choose something below that.

Now, for the Windows XP set-up. Everything went without a hitch until 27% of the file copy was completed. Then, it suddenly became impossible to read any more files from the CD. Hmmm. Was the CD ruined ? I tried a brand new OEM CD, and even a backup copy, to no avail. Then I tried yet another CD drive, and even another hard disk upgraded to the latest BIOS v35. Lastly, I tried the IDE cables.

None of these variables made a difference, so I surmised the motherboard had a faulty IDE controller. I phoned my retailer, and he said he would send me another system, but he would appreciate it if I tried some other RAM first. I thought it was weird that memory could give me these exact problems, but the CD players were DMA capable, so maybe there was something to this. I tried Twinmos, Samsung and Nanya memory sticks. None worked with my settings of DDR333 and CAS 2.0, even if the memory had these specs. Next, I lowered the speed to DDR 266 and CAS 2.5, and voila ! It worked with all memory types except my Corsair PC2700 CAS 2.0 stick. I had to lower to DDR266 and CAS 3.0 for it to work. No wonder I had problems. This defective stick went back to my retailer, and the replacement Corsair XMS worked with both DDR333 and CAS 2.0, so I concluded that the SIS chipset is very sensitive to memory timings.

Inserting memory/ IDE cables. A little tight in there. Make sure you don’t pull out the cables for 1394, USB 2.0 and front audio connectors.

Another setting that gave me headaches was the "Smart fan," since I had set the ’start’ temperature too high, causing the CPU to throttle and slow the XP set-up to snail speed. This was a little weird, because it would speed up every time I opened the door to my lab and let in fresh air.

Now, every known problem seems to have been solved, and XP installed without another hitch. Then I started listening for fan noise, and heard the AIW 7500 whining loudly. I had to decrease this noise. First, I disconnected the fan entirely to see if it ran stably in the way I was going to use it. I found I could watch half a DVD movie before anything happened. After that, the movie began stopping and restarting frequently, which was no good. I then connected a variable resistor in serial to the red fan cable. I determined that the fan running with 5 volts stopped when I set as little as 60 ohms of resistance, so I exchanged the resistor for one spanning 0-50 ohms. You may have to use a utility to underclock the card (if that is even possible), depending on what you use the card for. Only video-intense games strain the chip enough for it to require full fan speed. A good tip would be to drill a hole in the back of the case and install the variable resistor so you can adjust it on the fly.

AGP card modification. A simple variable resistor. My measurements on the fan showed I needed one able to handle 0.6 watts spanning 0-50 linear ohms. I calculated that the resistor needed to handle 0.6 watts, to be on the safe side. Any Radio Shack should have this part in stock.

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