Hi, my name is Erhard and Mr.Holub asked me if I was willing to take part in an interview for FLOP magazine. When I wondered what I should talk about I mentioned an interface that connects standard industrial floppy drives to the Atari, which I made in the late 90s. So I was asked to talk about this.
I live in Germany and for the time being I perform the floppy repair service for ABBUC.
The first contact with an Atari was in 1983 when a former colleague of mine wanted to upgrade to an Atari 800 while he wanted to sell his Atari 400. So I bought the Atari 400.
Then there was the usual progress with upgrading from slow datasette to an expensive Atari 1050 and to an Atari 130XE a bit later.
I performed my own memory upgrade to 192K and when I learned of a Happy 1050 upgrade I got one, too.
Mr.Holub: Why did you design the interface? It was because of insufficient original disk drives/floppies?
I heard of the maybe better or faster Speedy 1050 upgrade which I bought as well. But when it came to other floppy drives like the XF551 or the Floppy 2000 I was a bit annoyed by the relative small increase in capacity.
That's when I started to think about if it could be possible to run 3.5 inch drives of 1.44 MB with the Atari.
Mr.Holub: What kind of development tools have you used for firmware programming?
Since there was nothing on the market these days (appx 1996) (at least in Germany and except a hard drive on a MIO) I started to develop a single board computer (later called HDI) that should allow to connect the Atari to standard floppy drives via SIO.
Since I did not have Internet (did that already exist?) I wrote (snail mail !) to companies like Intel, AMD, Western Digital and others asking for IC data sheets and was very astounded when I was sent books. Nowadays they won't even read the letter ...
So I started creating some small PCBs that fit into the cartridge port so I could test chips like UARTs, RIOTs and FDCs individually from the Atari using a debugger. Btw, PCB design was done at the kitchen table using raster foil and symbols, the final PCB two-sided in 2:1.
When I had learned how the ICs worked I designed the PCB for the HDI. I had several prototypes along with fixes. The first boards were not drilled and I had to drill those 400+ holes myself. Then I had to manually throughcontact those 400+ holes and then populate the board.
Firmware development was like follows: I created an adaptor cable to connect the HDI CPU socket to the Atari 130 XE CPU socket and I disabled Atari memory from $4000 to $7FFF as the HDI's chips were in this area. So I could do programming tests using a debugger, Bug/65 to be exact and then write the real firmware in assembler using BiboAssembler. No idea why I didn't use Mac/65 by then. Maybe I did not yet have it.
Mr.Holub: What was the most difficult part of this project?
Everything was difficult and tedious, but I guess the most f**** task was to bring the SIO socket pins weird measuring to the PCB.
Mr.Holub: How long did it take to develop?
From start to ready product a bit more than 2 years.
Mr.Holub: Were there more units or just prototype?
It wasn't just a prototype. The final board was made by some company. When I had the first final boards for tests ready and populated I learned about ABBUC and went to some meeting, maybe that was the annual meeting in 1998. That's where I showed the HDI, a 3.5" 1.44 MB drive mounted on top of the HDI PCB. That's when people heard about it and I blindly ordered 50 PCBs from the company.
Then I started to receive orders. Most of them came from Germany but I had some orders from Austria, Great Britain, the USA and even one from Israel. In total I sold 56 HDIs. Well, imagine the fun with soldering 23000 pins.
Mr.Holub: What kind of formatting was used for floppy drives? Was it for standard 1.44MB disks?
I wanted to stay compatible to existing disk operating systems (otherwise the whole project would be useless) that were available for the Atari. Talking about higher capacities we only talk about MyDOS and SpartaDOS (later BW-DOS, too) and some others later still. SpartaDOS was my favourite anyway.
You can connect up to 4 standard drives to the HDI and it is possible to use a mix of 40 and 80 track drives. However the drives need to be able to provide the DC (disk change) signal on PIN34. The format for 1.44 MB is 36 sectors of 256 bytes per track per side. Well, of course you can insert a DD floppy into the drive and format it with 720K (2 sides x 80 tracks x 18 sectors per track x 256 bytes per sector).
Mr.Holub: Is there anything else you would like to add but I haven't asked?
Of course the HDI is no more available since some two decades. One could probably do a remake using newer chips but what for? There are more than enough mass storage peripherals available, the SDriveMAX for example.
The HDI may have been a very good solution in its time, but nowadays you can't even get floppy disks. Or at least it is difficult to put hands on new ones.
With Erhard by Mr.Holub
Erhard Puetz, the correct character to use is 'u' with umlaut and without the extra 'e', but such one is not included in the font used by FLOP, is a German fan of 8-bit Atari computers, active for many years. Apparently due to his interest in floppy disk drives, he has the nickname "Floppy Doc".
At meetings in Lengenfeld he often has his electronics tinkerer's apparatuses set up on his table and is researching or programming something.
In Czech Republic he often participates in events in the town České Budějovice, where he programs or plays games on a small Atari.