Re: Where to find HARD DRIVES nowadays???

[Michael Black <blackm00@Gloria.CAM.ORG>]

On Fri, 21 Jul 2000, John King wrote:

> There is a person working on an IDE interface for the Apple 2 and TRS-80 4P
> (at least those). Hopefully a published schematic and appropriate OS patches
> will put an end to such fears forever.
> 
> I was sort of surprised at how simple the TRS-80 4P to IDE interface was.
> 
But that's because the "IDE interface" is only a bit of glue to connect
the drive to the regular computer bus.

The interface is nothing more than some buffers, and some address
decoders.

An IDE hard drive isn't just a hard drive, but the hard drive controller,
that in years gone by would be plugged into a computer, with some cabling
to the hard drive.  Think of early IBM computers, and there was a card
with all kinds of IC's that plugged into the buss, that was the controller
card, and then two cables connected the controller to the mfm hard drive,
a 34pin cable and something like a 20 pin cable.  An IDE drive integrates
the controller card with the drive, eliminating those two cables, while
the "IDE interface" just has address decoding to map the controller into
the computer's address space, and a bit of buffering becuase you are
extending the computer's main bus.

Older "IDE interface" cards made this clear, because they only used
commonly available IC's.  Later, they started using some PAL's,
programmable IC's, to take care of some of the address decoding.
If present "IDE interface" cards look complicated, it's probably because
they are using a single multi-pin IC to put everything in one package.
But that doesn't mean the function of the IC is complicated.

Undoubtedly, the first problem of an "IDE controller" for an old computer
is that most people won't want to build their own.  So either a company
has to make such a board, or some group gets together to do it (as
was done for the Radio Shack Color Computer, though that project seems
to be way behind schedule).  But once the basic concept is conveyed,
making one is relatively simple.

The bigger problem is software.  Somebody has to write a driver to
go with this "IDE interface"/IDE drive combination.

    Michael