Re: IDE for C64

From: Marko Mäkelä (
Date: 1998-12-03 22:56:36

On Thu, 3 Dec 1998, Ruud Baltissen wrote:

> I just finished the HW of the interface to connect a IDE-harddisk with a
> C64.

Have you compared it with the one designed for the Oric, which is a 6502
computer? I think that the schematic is available either from
<URL:> or from Alexios Chochoulas' site
<URL:>.  I didn't find it at either
place, but I got the impression that they got the hardware running in the
summer of 1997.  As I haven't heard anything since, I think that they ran
into huge problems with software.

> Now the testing phase starts. FYI, it is built with 7 common available ICs.

Congratulations!  It is extremely important that there are no programmable
logic chips or other chips that are difficult to obtain. 

> The next problem is: what to do with the whole thing?

The German proverb "Good question. Next question?" applies here.  I think
that the programming effort is too big.  Interfacing the thing to the IEC
bus á la CMD's hard disks would be a waste of resources (both design
effort and computer resources; DMA transfer to the memory of the C64 would
be much faster), but it would ensure maximum compatibility (except with
fastloaders and copy-protected stuff).

I suggest that you use André Fachat's OS/A65 as a base for the system. 
Didn't he already have a filesystem implementation?  Emulating 1541-like
or 1581-like disks is not an option, since the maximum would be 255 tracks
and 256 sectors, which is less than 16 megabytes.  As someone recently
pointed out in comp.sys.cbm, it's not nice to divide a 4-gigabyte hard
disk to at least 256 partitions.

In my opinion, interfacing a hard disk directly to the C64 doesn't make
sense, except if you are religious about it and want to do without a PC. 
Speaking of which, last year you and Frank were playing with the thought
of connecting the C64 to a PC with DMA, so that the PC can access RAM and
I/O in the C64 address space without requiring any software to be
downloaded to the C64 first.  I'd like to see something like that in


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