Well, they would still need the raw buffer for every shot, no?
If they skip lines they don't need all of it, do they? Similarly to video mode... speed up readout by reading less. But maybe someone who has one of these cameras (S series? Others?) tell us how they work.
According to the specs, my A570 IS has 1.5 FPS burst mode (I never tried it though). Since people can use slower SD cards, it is reasonable to assume that there is such buffer.
This is just a spec for the regular continuous shooting mode, available in all shooting modes along with custom timer and the others. This burst speed drops if your card can't handle it. But now that you mention it, I don't think I've ever tested bursts thoroughly on a slow card (hint: those MMC's that come with these cameras are extremely slow). A pretty quick test should reveal whether the camera is able to buffer even one shot. I would think the cam could start shooting the next frame once it has finished JPEG encoding for the first shot, so it's to be expected that the delay between the first and the second shot could be shorter than all consecutive ones even if this extended memory area didn't exist.
The a570 can go on 'forever' with approximately that quoted 1,5 FPS in full resolution as long as no scaling happens, Tv is fast enough (duh), ISO is low (noise reduction processing is slow, if my mind serves me right ISO 200 and up start to slow bursts down...and this is separate from dark frame reduction) and if the card is fast enough.
Maximum burst speed is actually greater than that 1.5 FPS, it's achieved with the digital tele zoom feature cranked up to max 1.9x 'zoom' (==cropping from the center of the CCD) and JPEG resolution reduced accordingly to match the crop. I've measured 2.0 FPS at 1600x1200 this way.
Now, if this buffer can be found, and it is accessible by the ARM core, I think a lot of cool stuff can be done. For example, moving all the ROM in there, to be able to hook functions directly from the ROM.
I think there are some quite old posts you may want to try to find on these forums that I think discussed raw buffers... (no, I don't know where).
Anyway, if regular burst mode uses this area, then it's kind of a bad thing to use it for CHDK since everyday camera operation needs it. But of course sacrificing burst modes temporarily is no biggie if great things can be done this way.
