Reply 26180 of 27784, by Kahenraz
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- l33t
PD2JK wrote on 2023-12-11, 13:08:Kahenraz wrote on 2023-12-11, 12:38:PD2JK wrote on 2023-12-11, 09:30:A few days back I thought I blew an AT PSU, so I tried another PSU. Thankfully the short circuit protection kicked in. So after some inspection of the board, I saw this.
Why are there so many clock chips on that motherboard? I count no less than four from just that one angle.
I don't know. Maybe it's a (WD) Paradise thing, one some cards here I count just as much.
They even explain it at the bottom of the page. Very cool.
Paradise/Western Digital Crystals Most Paradise and Western Digital SVGA graphics cards come with 3 or 4 crystal oscillators, wh […]
Paradise/Western Digital Crystals
Most Paradise and Western Digital SVGA graphics cards come with 3 or 4 crystal oscillators, which are defined as follows:MCLK is the memory clock and determines the DRAM read/write access timing as well as the system CPU I/O and memory timing. MCLK should be 36 MHz if 120ns DRAMs are installed, and 42 MHz if 100ns or faster DRAMs are installed. This crystal should be of a higher value than VCLK0 and VCLK1.
VCLK0 is the video display clock (aka, the dot clock) for both text and graphics modes. At 25.175 MHz, this displays 640 pixels per horizontal display line.
VCLK1 can either be a second video display clock input or an output to an external clock selection module. If used as an input, 28.322 MHz is used to display 720 pixels per horizontal display line.
VCLK2 (if a fourth crystal is present) can either be a third video display clock input, or an output to an external clock selection module. If present it is usually 42.000 MHz or 44.900 MHz - don't confuse VCLK2 with MCLK. If the card also has a 36 MHz crystal elsewhere, that one is likely to be your MCLK crystal, and the 42 or 44.9 MHz one would be VCLK2. Your card might have a jumper to enable this fourth crystal, i.e. VCLK2.For 320 or 360 pixel modes, VCLK0, VCLK1 or VCLK2 is divided by 2 by the chipset to derive the pixel clock (PCLK).