How does the FDS video by-pass to the Famicom system video itself?

[ooXxXoo]

Hi Ya'll!
I've a technical questions for all of you Famicom stuff related experts...
I'm working on a project, and would like to know exactly how does the FDS video output gets into a Famicom system when attached together....
Hopefully someone already knows before I go on taking my systems apart...Thanks in advance!..

[133MHz]

The FDS doesn't generate a video signal at all, not even the RAM adapter. The only non-digital data that it provides is an analog extra sound channel that gets mixed inside the Famicom with the normal sound from the CPU. All video work is done by the Famicom's PPU, the FDS only provides data like a normal cartridge with extra sound hardware.

You're thinking Sega. The 32X overlays its video signal on top of the Genesis one, usually the Genesis draws the background while the 32X draws the sprites, both signals get composited together and you get the sum of both images. That's the purpose of the cable that connects the 32X to the Genesis, carrying the RGB+Sync signals to the 32X.

[nintendodork]

I always found it funny how you could simply plug in the RAM adapter of the FDS into the Famicom and it would still turn on with out a power supply or even plugging the RAM adapter into the Disk System

[133MHz]

The RAM adapter is like any other cartridge, it gets its power from the Famicom, and the FDS drive isn't more than a custom Mitsumi Quick Disk drive, there are no other logic chips inside it besides the drive controller (and write lockout chips on large power boards). Nearly everything is done by the RAM adapter itself.

[nintendodork]

Ah, ok..but Nintendo should have made the whole Disk System just run off the power of the Famicom instead of bulky AC adapters or 6 huge C batteries

[ooXxXoo]

Oh, Thanks for the heads up!....That's exactly what I was thinking, just wanted to make sure since I'm fairly new at messing with FDS stuff....

[133MHz]

Me too, but the motor is the biggest power drain in the FDS (around 250mA during operation) and running it off the Famicom's power would have worked in the short term, but it would put unnecessary stress on the Famicom's voltage regulator and AC adapter which will lead to reduced lifetime of said components and failure in the long run (remember that a motor is an inductive load, and switching it on and off produces voltage spikes).

Basically Nintendo played safe and avoided a Xbox 360 RRoD type fiasco.

[nintendodork]

Wow, I can't believe I was thinking like M$ instead of Nintendo....
I just blew my mind