On Sun, Apr 29, 2001 at 07:15:11PM -0500, James West wrote:
>
> Actually -in- the dreamcast itself, which lends the question, how do we get 
> at it? If there is an IDE bus that is accessible, this lends more 
> possibility to the idea of hooking up an actual hard drive to the unit. 
> Since the zip drive was supposed to be all self-containted, I'm assuming 
> enough current runs through the modem port to power a small drive.


The simplest form of IDE is called something like PIO mode 1.  Basically,
the registers of the drive are mapped somewhere to the processor's memory 
space, sometimes through a special interface.  Through the control registers, 
you can tell the drive to read or write cylinder X, head Y, sector Z.  
Then you pass the data through one of the data registers.  

This is probably what that guy built, just an address decode / chip enable 
circuit and probably some buffers.  

Using DMA modes of the drive are more complicated... because it involves 
programming the DMA controller (assuming there is one).  But doing the 
simple PIO mode 1 (roughly 2-3 MB/s) should be very easy.  Of course, you 
have to build the completely custom hardware, which limits the mass appeal.  


Brendan Dowling