Question about the maximum number of line you could draw

[LamerDeluxe]

I've made a small demo today that draws a lot of pulsing, rotating and scaling rectangle line sprites. At 40 it already gave me an 2K RAM buffer error. At 30 (120 lines, no extra segments) it worked.

Is there less of a limit when using lower framerates?

I guess there a no sprites or primitives stored in the memory of the Vectrex that are re-referenced. I guess the position/rotation/intensity commands also add to the memory use. So is this amount of lines about the maximum that the Vectrex32 RAM can handle? Because some of the native Vectrex games seem to be able to handle a pretty large amount of lines (the animating CD of Protector/YASI for instance).

[Vectrex32]

Frame rate would affect the amount of drawing the Vectrex can do, but would not affect what can fit in the 2K RAM.

You're right about all the stuff that goes into the 2K RAM. YASI is using a clever scheme that, if I understand correctly, is similar to how the Vectrex draws text. Each raster is just one line, but the brightness is turned off and on while the line is being drawn. The V32 does not have that ability built-in (though it might be possible to do with a Code Sprite).

- Bob

[LamerDeluxe]

That is a cool trick, pretty much how a normal CRT works. Would more dual ported RAM even be possible with the Vectrex? How much would that increase the price?

[Vectrex32]

More DPRAM would be technically possible. I haven't looked into how much more it would cost. Not only would the chip itself be more, but it's a bigger chip with more pins so assembly is more challenging (and beyond my ability to solder it myself).

- Bob

[LamerDeluxe]

I see, so that would require a redesign of the board. Would be interesting ttofind kut what would max out the abilities of the Vectrex.

So you solder these by hand, that is a lot of work.

Looking forward to trying some more ideas for demos. Interestingly I haven't had any weird glirches while developing.other than the occasional blank frames while a demo is running.

[LamerDeluxe]

What would be the maximum amount of dual ported RAM that the Vectrex could handle?

[Vectrex32]

The max amount of DPRAM would be 32K.

I hand soldered the prototypes. I pay someone else to assemble the production boards because my failure rate with making them is about 25%.

- Bob

[LamerDeluxe]

32K that is pretty luxurious. So the Vectrex can access that memory directly? I wonder how much memory it would take to max the Vectrex out in what it would be able to draw at say, 25 fps.

To me that even seems like a pretty good failure rate, I haven't dared to even solder any kind of SMD component yet.

I've been working on a more extensive demo. If I wanted to post a demo, would I do so in the games section? Or would it be an idea to have a separate demo section? It would probably be educational to have small demos there as well.

[Vectrex32]

Well the 6809 can access 64K and the Vectrex maps half of that, 32K, to the cartridge port.

If you want to post a demo, maybe the Code Swap forum would be the best place.

- Bob

[LamerDeluxe]

Cool, I think that is similar to how the Gameboy uses cartridges. How many bytes are the commands that are sent to the Vectrex? Three for move/draw commands?

Will post something to the code swap section when I have something worth sharing.

[Vectrex32]

The commands sent to the 6809 are just straight assembly language, so they vary. Typically, they set up arguments and call a BIOS routine.

- Bob

[LamerDeluxe]

Really cool, that should give you maximum performance. That explains the code sprite as well. Must have been a lot of work to develop.

I talked to someone who makes demoscene demos and he was really interested in the Vectrex 32. He said it is pretty inexpensive for homebrew hardware. Should you create one with more RAM or even the full 32KB, if that could be utilized, I would order one right away.