Locomotive BASIC - 32en40 by 'Quetzalcoatl & Kukulcan'

Started by ComSoft6128, 16:29, 05 January 22

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ComSoft6128


French utility from 1991.
So, what do we have have here?
I'm not sure...it seems to convert 32 column screens to 40 column screens but what exactly is a 32 column screen?
A Spectrum screen ported to the CPC?
If anyone can explain this please do.
Program is Listed at end of video.



https://www.youtube.com/watch?v=AlWvOQpWIhI&t=6s


Link:
https://www.cpc-power.com/index.php?page=detail&num=4845


Not emulated - original hardware and software.
Please note that  the aspect ratio for this YouTube video is 16:9 but the CPC monitor
has an aspect ratio of 4:3 so you may wish to adjust your viewing device accordingly.


arnolde

A lot, if not most, of CPC games use 32 instead of 40 columns. The screen is smaller but it allows programming much faster graphic routines (sprites!). But if you are in the standard 40 column width mode and load a loading/title screen for 32 columns the usual way, it's scrambled. That's what this utility fixes.
Try this and you will understand:

mode 0
load "planet32.ecr",&c000

pelrun

If you try to load a screen that's been formatted to need the smaller speccy viewport size without reprogramming the CRTC first, it'll come up garbled. This just redraws it into the wider standard CPC screen format so a simple LOAD"image.bin",&C000 will appear correct (if the inks/mode are set properly, obviously.)
@arnolde, the reason it was done (and why so many games on the CPC did it) is because it was cheaper and faster to do a low-effort port from an existing Spectrum version of the game than to develop the CPC version independently. The Speccy used the smaller viewport size, so the ports generally just reprogrammed the CRTC to the same dimensions so they didn't have to redraw graphics or rewrite all the drawing code. The smaller size doesn't make drawing routines any faster on the CPC; in fact speccy ports are invariably a lot *slower* than the original spectrum games because the spectrum has attribute colour and the CPC doesn't. 

arnolde

You're right about the bad Speccy clones: Without any effort and no will (or time) to reprogram stuff properly, they ended up running slower.
But there is a lot of original software for CPC in 32 column mode and if you do it properly, you can indeed speed up the graphics drastically. Take a look at classics like Exolon or Gryzor: They all run in 32 columns.
Also a very good artivle about that here on the Wiki: https://www.cpcwiki.eu/index.php/Programming:Fast_Sprites

ComSoft6128

Quote from: arnolde on 17:04, 05 January 22
A lot, if not most, of CPC games use 32 instead of 40 columns. The screen is smaller but it allows programming much faster graphic routines (sprites!). But if you are in the standard 40 column width mode and load a loading/title screen for 32 columns the usual way, it's scrambled. That's what this utility fixes.
Try this and you will understand:

mode 0
load "planet32.ecr",&c000




https://www.youtube.com/watch?v=_q7CU5umaGg

arnolde

Exactly - that's why it has to be converted ;-)

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