Watching VSP&IK+ (C64)

We’ve got another piece of C64 scene history today, the Mean Team’s VSP&IK+ from 1987. This is another of those demos from the “Wild West” period when programmers were as much concerned if not more so with getting their latest creations out there and the name is pretty much self-explanatory; the IK+ part comes from the music by Rob Hubbard and Paul “Dokk” Docherty picture which were both being taken from the game of the same name, whilst the VSP refers to it being the first instance of Variable Screen Positioning, a hardware “feature” similar to but much harder to implement than the more common Flexible Line Distancing – FLD to its friends – which was in common use around that time.

This technique is sometimes referred to as DMA delay because that’s essentially how it works, waiting for a badline where the C64 fetches screen data and fooling the VIC-II into waiting for a fixed amount of cycles before that fetch actually takes place by setting the vertical scroll register to a value that won’t see it happen, then changing back to one where it will later in the line. One cycle equates to the width of a character so waiting five cycles will push the screen right by that many characters and it’s possible to travel an entire screen width, with the data wrapping around onto the start of the next line, something this demo masks by changing the attribute data. VSP-based scrolling is how games like Mayhem In Monsterland can move their backgrounds so quickly.

I remember seeing VSP&IK+ for the first time on a friend’s C64, casually thinking “oh that’s nice and smooth” in passing as it started up and the picture slid smoothly in from right to left and then staring in disbelief as it snapped back in the other direction at far too great a speed to merely be a double buffered bitmap scroller – we already knew about FLD and understood how it worked but this was nothing short of witchcraft at the time! It still makes me smile now despite knowing how the routine works and having my own examples.

Watching Demo Factory (C64)

Let’s do something a little different and look at one of my own demos, specifically Demo Factory on the C64 from 1987. The original idea came about from a brainstorming session with friends and was intended to be a less than serious response to the plethora of bog standard demos around at the time which usually included a bitmapped picture, some music and a sprite-based ROL scroller in the border. We all found the idea of an automated factory churning these similar-looking demos out on a conveyor belt amusing so I set about programming, pausing only to work things out on paper first – something I haven’t bothered doing since – and to read up on how the hardware sprite priority registers worked from the C64 Programmer’s Reference Guide.

Looking back now the code itself is embarrassingly simple – even more so than I remembered it being in fact – but in my defence I was still learning assembly language and indeed the C64 at the time. The music is Rob Hubbard’s Hunter Patrol theme which arrived as a file he’d uploaded to Compunet that had the music located low in memory and started an IRQ to play it before dropping back to BASIC; my code calls that and executes behind it, using timing loops rather than actually waiting for a rasterline or anything sensible because I didn’t know better. I’m tempted to call this my first “real demo” because, despite there being a few releases prior to it including Past Shock, this was the first time I managed to get action on the screen with someone else’s music playing.

The “logic” was, if I recall correctly after three decades, that a parody didn’t have to be particularly well programmed because shonky code could be passed off as part of the joke; similarly, the lack of a scrolling message was absolutely part of the “protest” against bog standard demos and not in the slightest because I couldn’t get one working or anything like that… honest! There’s also a healthy whiff of irony and very probably hypocrisy about me of all people railing against the bog standard demo as a format since I’m incredibly fond of it as a format, was inspired to start coding demos by releases like Future Shock and have since programmed several releases over the years which stick to that tried and tested formula.

I’ve considered doing a remixed version of Demo Factory on a couple of occasions previously which would be an overhaul of the graphics and actually running from interrupt with all the benefits that would entail; it could perhaps animate all of the elements of the demo making machine that I wasn’t able to handle back in 1987 as well and, just for the sake of irony, would probably include a scrolling message as well…?

Watching Crazy Demo (C64)

Crazy Demo by the Norwegian Crackware Company was released way back in 1985 and the style is reminiscent of other releases around that time like the titles page of the Flying Crackers’ game Crackers Revenge; it’s bright and delightfully cluttered with multiple scrolling messages poolting past, some elements pulsing through the C64’s five shades of grey and a sprite logo pushed into the lower border. All of this is accompanied by Rob Hubbard’s Crazy Comets soundtrack, which works well regardless of which tune has been selected via a prod of the space bar.

This is a fun one-parter which came up during a Facebook discussion about the origins of the demo scene a couple of days ago, with former NCC member Stein Pedersen – currently a member of Offence, Prosonix and Panoramic Designs -posting a link as the topic slowly suffered a little bit of “feature creep” and drifted off into the realms of early demos. It was subsequently accompanied by a further tangent about classic Doctor Who titles sequences because they look a bit like demo tunnel effects, so that was me pretty much happy for the rest of the day.

It’s always interesting to see where people started out and, whilst it isn’t a C64 milestone in the same way that a couple of the other demos I’ve been squinting at recently like Readme.prg was for the Atari ST, Crazy Demo is still an early step in a fantastic demo programming career and a lovely example of C64 releases from that time. On a related note, I’m now stuck with the Crazy Comets theme rattling around my head for the rest of the day. Again.