Re: Not your father's Applicard

Steven Hirsch wrote:
MdntTrain wrote:

I'm a
software guy with enough digital hardware knowledge to be dangerous (now,
analog audio systems are another story, but who uses them anymore?).

Well, I do for one. And tubes.. and vinyl... :-)

Cool. I grew up with audio and have it in my blood. My late father, Julian Hirsch, was a well known audio reviewer and technical writer. After years of striving for the utmost accuracy in analog reproduction, I think he would have found it somewhat upsetting to see devices using lossy compression (e.g. iPod, MP3 players, etc.) take over so much of the market.

I think the market has decided that being able to carry your whole
music library in your pocket and listen to it with "acceptable" fidelity
anywhere is preferable to being able to listen to it with excellent
fidelity, but only in one room of your house.

IOW, good enough anywhere is "good enough"--particularly since it's
as good as or better than most people are used to hearing anyway.

Moderately good ear buds deliver pretty good dynamic range, but
progressive hearing damage has taken much of the mass appeal out
of "pure audio". ;-)

I still have have about 400 vinyl LP records, although I've been chipping away at transcribing them to CD (48Khz. PCM, NOT MP3 thankyou-very-much). I'm one of those folks who refuses to buy something twice just to have it on different media :-).

My collection is similar, and I received a USB turntable as a
present, so maybe such conversion is in my future. Now, if I could
just get a robot to keep putting the disks on the turntable and
turning them over. ;-)

The nice thing about Alex's upcoming FPGA project
board is that you can implement the 6809 (or, better yet, 6309) in
synthesizable logic and have enough room left over for two or three more CPUs.

You mean YOU could implement it. I wouldn't have the foggiest idea
of how to put a CPU core on an FPGA, much less the entire Mill card.
I'd like to learn, but man, what a stretch. My brain is back at 7400
series.

Don't get me wrong! I'm not anywhere NEAR far enough on the learning curve to code a CPU in VHDL. But, I think sewing together modules written and tested by others isn't beyond my grasp. I've been spending a lot of time reading through every book I can get my hands on, rewinding all the way back to the fundamentals of Karnaugh maps and by-hand logic minimization. I actually knew this stuff reasonably well when I got my CS degree, but never worked in the hardware domain and it sort of dissipated.

It's getting harder and harder to tell the difference between a hardware
designer and a software designer by looking over their shoulder!

How about this idea. If Alex introduces his FPGA kit, what about a
group effort / learning project to recreate the Mill on his card?
All in the group would commit to purchasing Alex's card, then we'd all
help each other learn about it and make kinda like an Open Source
project of getting a Mill, docs, and software all organized. A
project like this would help legacy brains like mine learn about the
newer technologies.. it'd be a great thing that'd go beyond just a
Mill card... especially if enough people would get on board.

I'm always up for a challenge, so why not? The first order of business is to find some architectural information on the 6809 Mill. The second is to reverse engineer the little piggy-back board that made it possible to run OS-9 on the Apple. If the implementation is anything like the CoCo (a good bet), memory re-mapping is a requirement. Everything in OS-9 is fully relocatable and it dynamically maps logical <---> physical address space in 4k chunks. My CoCo has 512K installed and it's able to use all of that by swapping these chunks into the 64k address space as needed by the currently running task. Task switching is triggered by a hardware timer interrupt. Quite sophisticated for a little machine.

The 6809 architecture is not really very similar to the 6502, and is highly optimized for relocatable, PC-relative addressing.

Of course, like all 68* machines, it's big-endian, so data exchange with
a 65* machine is a bit of a pain...

-michael

******** Note new website URL ********

NadaNet and AppleCrate II for Apple II parallel computing!
Home page: http://home.comcast.net/~mjmahon/

"The wastebasket is our most important design
tool--and it's seriously underused."
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