3dfx Archive - Chrontel & Atmel chips on Pure3D cards

NitroX infinity

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Chrontel & Atmel chips on Pure3D cards
15.01.11 at 18:14:42

I'm sure these chips are on more cards than just the Pure3D's from Canopus but that's not relevant to the question I have.

On the Canopus we find a Chrontel chip, this chip turns VGA signals into PAL/NTSC signals.
http://www.datasheetcatalog.org/datasheets2/20/204066_1.pdf

However, there's also an Atmel chip;
http://www.atmel.com/dyn/resources/prod_documents/doc0364.pdf

As far as I can tell from reading the datasheet, it's a PAL emulator. I'm sorry, what? Why would there be a need for an emulator if there's already a converter (the Chrontel chip) ??

Can somebody please explain the function of that Atmel chip to me? How does it relate to the Chrontel chip?

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goriath God Member Offline Ruggedized Retro Gamer Posts: 599 Italy/Slovenija Gender:	Re: Chrontel & Atmel chips on Pure3D cards Reply #1 - 15.01.11 at 21:50:26 Emulation? No, nothing to do with emulation. The atmel is a CMOS chip, with an erasable and programmable flash memory area, just like many eeprom bios chip on motherboards and VGA.
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NitroX infinity YaBB Moderator Offline Posts: 1936 The Netherlands Gender:	Re: Chrontel & Atmel chips on Pure3D cards Reply #2 - 15.01.11 at 22:08:15 Then, what is it's function on the Voodoo cards?
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RaverX God Member Offline Voodoo2 fan Posts: 533 Oradea, Romania Gender:	Re: Chrontel & Atmel chips on Pure3D cards Reply #3 - 16.01.11 at 00:44:32 NitroX infinity wrote on 15.01.11 at 22:08:15: Then, what is it's function on the Voodoo cards? Isn't obvious ? It stores the videocard BIOS.
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exxe God Member Offline ^^ Posts: 1316 germany	Re: Chrontel & Atmel chips on Pure3D cards Reply #4 - 16.01.11 at 10:04:17 u20 can also be used with an other, smaller IC as far both ICs missing on the non TV-out version i would say both chips are need for the TV-out http://tdfx.de/pic/pure3dlx_01b.JPG http://tdfx.de/pic/pure3d_01b.JPG
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NitroX infinity

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Re: Chrontel & Atmel chips on Pure3D cards
Reply #5 - 16.01.11 at 13:52:18

RaverX wrote on 16.01.11 at 00:44:32:

NitroX infinity wrote on 15.01.11 at 22:08:15:

Then, what is it's function on the Voodoo cards?

Isn't obvious ? It stores the videocard BIOS.

Voodoo Graphic cards do not require a BIOS. Though I suppose it could be used to store information about PAL/NTSC resolutions?

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goriath

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Re: Chrontel & Atmel chips on Pure3D cards
Reply #6 - 16.01.11 at 14:49:49

NitroX infinity wrote on 16.01.11 at 13:52:18:

RaverX wrote on 16.01.11 at 00:44:32:

NitroX infinity wrote on 15.01.11 at 22:08:15:

Then, what is it's function on the Voodoo cards?

Isn't obvious ? It stores the videocard BIOS.

Voodoo Graphic cards do not require a BIOS. Though I suppose it could be used to store information about PAL/NTSC resolutions?

No, it couldn't.

Look at the pictures posted by exxe (thank you, exxe). You should notice an important difference between the two layouts beyond the atmel and chrontel chips.

Every Voodoo Graphics chipset (as every VGAs chipset) needs a crystal oscillator, in order to stabilize the chipset pixel clock signal. This is important to provide a stable image on the screen, at fixed resolution and refresh. Looking at first picture, you can find the crystal oscillator at the bottom of the card, under the ICS gendac.

But in the second picture, which displays the layout with TV out capabilities, the crystall oscillator is placed in the upper part of the board, beside the chrontel chip.

Now, also the chrontel chip need a crystal oscillator, but as you can see, there is only one. My guess is that the atmel chip is used as crystal oscillator replacement Wink

You can read the description for pin 17, page three of chrontel datasheet, to find a confirm about that.

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G1nX Senior Member Offline Running NSK Guardian Posts: 466 Romania Gender:	Re: Chrontel & Atmel chips on Pure3D cards Reply #7 - 16.01.11 at 16:37:01 To me it looks as both cards have a quartz just in different locations Y1 vs Y2. As to the Atmel chip I was thinking that i might have something to do with the special features Canopus provides with it's sw like the Witchdoctor setup to pass all signals to the Spectra2500. My two cents on the matter. Cheers, G1nX
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goriath

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Re: Chrontel & Atmel chips on Pure3D cards
Reply #8 - 16.01.11 at 16:49:05

G1nX wrote on 16.01.11 at 16:37:01:

To me it looks as both cards have a quartz just in different locations Y1 vs Y2.

Right, but in case of TV capabilities, the chrontel chip would need a crystal oscillator as well, while in the TV version of the card you can see there is only one oscillator.

This could be explaned by the presence of the atmel chip indeed, a replacement of the crystal oscillator.

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G1nX

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Re: Chrontel & Atmel chips on Pure3D cards
Reply #9 - 16.01.11 at 23:02:16

You only need one quartz because it serves the same function it only depends if it will handle VGA only or VGA + TV-out thus the different location on the board. See a similar scenario on Rush cards:
http://www.tdfx.de/pic/helios_rush_01.JPG
http://www.tdfx.de/pic/adrenaline_rush_01.JPG
An these don't have an Atmel chip only the BIOS chip (various brands).

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