1541 intro

[shoestring]

 

[carlsson]

When you thought every trick in the book was already exploited. A little sad about the video and serial cables but I'm sure he had spares. I've read about other people with similar ideas, using commonly available microcontrollers to generate both video and audio, but then again it would become a completely different platform. This one is 6502 based and relies on the C64 to first load the drive code to be programmed into the drive memory.

 

IIRC the 1540 has some obscure autobooting feature (&) that the 1541 removed, or maybe I'm thinking of the 1571? I wonder if you can utilize both IEC connectors on the 1541, but then again daisy chaining can't address a single of the two connectors from what I remember.

[+OLD CS1]

3 hours ago, carlsson said:

IIRC the 1540 has some obscure autobooting feature (&) that the 1541 removed, or maybe I'm thinking of the 1571?

This rings a bell.  I know it exists on the 1581 and 1571 ("Utility loader,") but ISTR it being available on another drive but not the 1541.  The 1540 manual does not list the &0: filename or the utility loader.  Maybe it was a hidden DOS thing?

 

4 hours ago, carlsson said:

I wonder if you can utilize both IEC connectors on the 1541, but then again daisy chaining can't address a single of the two connectors from what I remember.

You can get the serial port to do whatever you want from the 1541, but, as you say, the ports are not independently addressable as they are electrically joined on the controller board.

[carlsson]

There are firmware versions here: http://www.zimmers.net/anonftp/pub/cbm/firmware/drives/new/1541/

 

Apparently if CLK and DATA are low, it will automatically load the first file, but then again I suppose it sends the data as is to whoever is listening, not loading the data into the drive's own memory to execute. I'm sure the demo coders right now are looking into ways to refine this technique and come up with even crazier tricks.

[+OLD CS1]

@shoestring Mad sunnuvabitch!

 

Consider a few things about this demo.  The 1541 only has 2k of RAM, so the entire demo had to fit into that space of memory. Being it is monochrome, I can imagine it is a simple bit stream, perhaps compressed.  Second is that video signals are a kind-of voodoo, and to generate a video signal using nothing but the 6522 VIA is quite impressive downright awesome.  Note that the clock line is most likely the source of magic here, as it can be timed on the VIA much faster than the CPU can command the chip to toggle a line.  If those are original CBM cables that got sliced up, I am of two minds: they are old and probably need modern replacement, but then they are original and must be preserved!

 

I get a chuckle out of the thought of this being released at a compo, and someone walks up to the desk carrying nothing more than a 1541 rigged up with a power supply.

[+OLD CS1]

@carlsson To clarify, from what I can see, only the 1581 has the ability to auto boot a file, wheres all three drives have the utility loader ("&") command.

 

From the 1581 manual:

Quote

AUTO BOOT LOADER

During some operations (power-up reset, burst INQURE, burst QUERY, an initialize command) the 1581 will automatically look for a file or the disk named 'COPYRIGHT CBM 86' that is a USR type-file. The format of the file is the same as that described previously for the utility loader. If it is present, the file is automatically loaded and executed.

 

I suspect this demo could easily be run on a 1581 from a disk auto-booting this file.  Should just be triggerable by powering it up rather than the write-protect sensor on the 1541.

[BydoEmpire]

That's pretty amazing.

[shoestring]

On 7/5/2021 at 1:07 AM, OLD CS1 said:

@shoestring Mad sunnuvabitch!

I those heads are now misaligned. 

[+OLD CS1]

3 minutes ago, shoestring said:

I those heads are now misaligned. 

heheheh Banging on the head-stop, sure, but it sounds like it was just using the stepper motor motion.  Similar to the HP ScanJets used by the Floppotron.

[+OLD CS1]

On 7/4/2021 at 11:07 AM, OLD CS1 said:

Note that the clock line is most likely the source of magic here, as it can be timed on the VIA much faster than the CPU can command the chip to toggle a line.

I just watched this a third time an realized how woefully wrong I was here.  These are not VIA shift register lines... this is all actually CPU-driven.  Holy schmoly!  The impressive level jumps 10x for me.

 

Although, he loses points for disconnecting the video and serial cable with the computer still powered on.  This is a direct violation of the instruction manual

[+OLD CS1]

There is also some squealing in the background of the video, which sounds to me like the monitor may not particularly like the signal it is receiving but is displaying with minor protest in the really high registers.  You can see a few times where the monitor seems to lose sync with the signal being generated for a split second.  During the low register sounds in the music stream you can almost hear where the head is on the travel.  It does sound like it bangs the head at a transition point of the demo, but it does not sound any worse than when the drive does so of its own accord, like during a read error.

 

I would love to see this demo on hardware.  There is so much going on here.

[shoestring]

I'm not sure how its done but I prefer not to think about it. 've watched it several times as well. When a disk drive has better video & sound capabilities than some 8 bit home computers