Phone getting HOT with TDMA, not with GSM

[Shizam76]

I noticed something yesterday. At work I made a few lengthy calls on my Nokia 6340i with Cingular, like 20-30 minute calls and the phone did not get hot like my old TDMA used to with the same length call. Now last night my phone was in TDMA mode (I usually check before calling and power cycle if needed, but I didn't check this time) and made a call without thinking. The phone started to get really warm after about 10 minutes and I checked and I was on TDMA.

What is it about TDMA that causes the phones to heat up on lengthy calls?
Why does GSM not heat the phones up lengthy calls?

[Bugwart]

What gets hot are the chipsets. Newer chips are made with much smaller geometries than older ones. Smaller geometries mean less heat produced for the same functions.

I know that Nokia and many other handset makers have worked hard to make GSM chipsets as efficient as possible. The benefits are improved battery life, less heat, smaller size, etc.

I would highly doubt if anything approaching the same effort has been done with TDMA chipsets. Why spend many millions on optimizing a design that will be phased out in the near future?

I would guess that TDMA chips trail GSM chips by 2 or 3 generations. Thus, TDMA chips will produce more heat than GSM chips during calls of the same length.