Re: TP755C/CE differences?

["Robert George" <george@holmes.cs.nps.navy.mil>]

On Jan 19, 10:37am, Chuck McManis wrote:
> Subject: Re: TP755C/CE differences?
>
> The 755C is a 750C with a faster processor, it cannot be upgraded to a
> 755CD.
>
> The 755CE has a new motherboard and a new sound subsystem. The sound
> subsystem uses IBMs "MWave" DSP sound chip that can, among other things,
> act as a 28.8K modem (this saves you a PCMCIA slot). Allegedly (and I've
> not confirmed this) the MWave chip is also _register_ compatible with
> the Sound Blaster so many more DOS tools work out of the box without the
> generally unreliable sound blaster emulator driver. Finally the CE, unlike
> the C can take video *in* and display it on your screen. This is due to an
> enhanced LCD display that can display 64K colors simultaneously, to the
> 755C's 256.
>
> --Chuck
>-- End of excerpt from Chuck McManis

The number of colors the LCD panel can display has little to do with the panel
itself.  Active matrix LCD panels are _analog_ displays, much like a
television. Each pixel has an analog (non-switching) transistor driving a red,
green, and blue pixel.  This means that the panel itself can display an
infinite number of colors simulaneously.

The limitation of the ThinkPad's is due to the graphics chip which is driving
the panel.  The 755C's have an 8 bit chip driving the RAMDAC which converts the
digital output of the VGA chip to analog LCD signals.  The 755CE's have a
16-bit chip.

On a similar note, all 750 and 755's *can* display video.  I played with the
ThinPad television tuner which fits into the floppy drive bay in the 750 and
755's.  The screen quality for television broadcasts was actually quite good.
 Although the unit is outrageously expensive ($2000!), it has a very nice
feature: an external video input.  I was driving the screen of the ThinkPad
with a color CCD camera -- very nice.

Robert