Recent posts

#1

Emulators / Re: Is there an emulator where...

Last post by eto - Today at 14:14

Retro Virtual Machine (2) has this feature and I am pretty sure that WinApe has it.

I didn't find it in RVM but now I saw it. Thanks. 

#2

Games / Re: Could "Turrican" be made b...

Last post by abalore - Today at 13:25

With 8 pixel character height you can easily do 1 pixel scrolling, the CRTC has a specific register for that. And you don't have to update all the 8 pixel row per frame, you can do it in 8 steps, so the Z80 usage is the minimal required. I don't see how a 2 pixel character height would work without having to change the display start address in each block and without having to make a painful sprite drawing routine.

#3

Emulators / Re: Is there an emulator where...

Last post by Longshot - Today at 12:33

Retro Virtual Machine (2) has this feature and I am pretty sure that WinApe has it.

You can't do that with WinAPE.

#4

Emulators / Re: Is there an emulator where...

Last post by TotO - Today at 12:23

Take a look to AMSpiriT, it is probably the more accurate for that:
https://www.cpcwiki.eu/forum/index.php?msg=218889

#5

Emulators / Re: Is there an emulator where...

Last post by BSC - Today at 10:03

Retro Virtual Machine (2) has this feature and I am pretty sure that WinApe has it.

#6

Emulators / Is there an emulator where I c...

Last post by eto - Today at 08:46

Is there an emulator in which you can manipulate registers in the UI directly, e.g. those of the CRTC?

#7

Games / Re: Could "Turrican" be made b...

Last post by eto - Today at 07:51

It only matters what the Z80 does. The less you shift the screen, the less RAM the Z80 needs to change. The CRTC does it's work independent, like all other chips too.

That's my point really, Z80 has to update the screen and outside of the Z80 processing time the screen is updated via the CRTC.
Which brings me to the point that 2 pixel character screen setup has no advantage over 8 pixel characters  Smooth vertical 1 pixel scrolling is completely independent of vertical char size or 1 byte horizontal scrolling.

That's what I understood from Gunheds post: When you scroll the screen by one character, the CPU has to update that part of the screen, that is shifted out of one border and into the opposite border. Otherwise your screen would not scroll, but roll. With a character height of 8 lines, you have to update 8x 80bytes and with a character height of 2 lines, you have to update only 2x 80bytes. 

What I am still missing: What are the CRTC settings that allow to generate a 320x200 screen with a character height of 2 lines? If that exists, let's try it out.

#8

Amstrad CPC hardware / Re: Easiest way to turn on/off...

Last post by eto - Today at 07:30

Eventually you can use the LEDs of the LambdaSpeak.

I don't have that. I used the printer port idea as it's easy to build. 

But I want to check if your idea with the drive LED is feasible. That would be even better, as it means, you can test your screen lag with nothing but your CPC and a smartphone. 

#9

Amstrad CPC hardware / Re: Gate array decapped!

Last post by jb2590 - Today at 05:28

Yes, I'm sure it should be fairly inexpensive to post. I'm most interested in determining if this supplier is legitimate or not. With the new CPLD option it will certainly ease the necessity to source original chips, but it would be nice to see if the source actually is legitimate and has a good stock of chips available.  

#10

Games / Re: Could "Turrican" be made b...

Last post by lmimmfn - Today at 04:07

What tricks could you try to enlarge the game window with the same or better framerate?

- Use screen 64 byte in width (32 x 32 characters in MODE 1, but here MODE 0 would probably look more nice)
- Use CRTC characters only 4 scanlines high, or even better only 2 (instead of 8 like usually), this will make the scrolling more smooth, also gives extra time, because less V-RAM needs to be moved.
- instead of having sprites as data, use something like CoData (I use that for Filmemacher). Basically a program which draws the sprite or graphic element on screen. That's more quick compared to copy data.
- Use more RAM, this enables to unroll routines which contain loops. Also a speed up.

And finally: Do a complete rewrite instead of patching / enhancing / bettenering / etc. of an existing program. Alcon 2020 may serve as a well example for that ;-)

Excuse my ignorance but on
"Use CRTC characters only 4 scanlines high, or even better only 2 (instead of 8 like usually), this will make the scrolling more smooth, also gives extra time, because less V-RAM needs to be moved."
How does that make scrolling smooth? The CRTC has a fixed number of cycles to read the ram separately to the Z80, so how does reducing the character scanlines improve performance if its still a full screen(32x32)?
The CRTC is still working outside of the Z80 for screen refresh so I don't understand the comment.

The regular character line height is 8 scan lines. So you need to transfer data for 8 scanlines every frame in case you want to scroll up or down.
In case you use only 2 scanlines, then you only need to transfer 1/4 of the data. In addition scrolling is more smooth and slower.

Wouldn't that also make the screen 1/4 height? Or am I missing something?

No, just use more character lines. 25 * 8 = 200 scanlines. 100 * 2 = 200 scanlines too.

But why is that different, its the same amount of screen update from the CPU and the CRTC is updating a full screen, where is the saving coming from? Not trying to be argumentative, I just don't understand.

It only matters what the Z80 does. The less you shift the screen, the less RAM the Z80 needs to change. The CRTC does it's work independent, like all other chips too.

That's my point really, Z80 has to update the screen and outside of the Z80 processing time the screen is updated via the CRTC.
Which brings me to the point that 2 pixel character screen setup has no advantage over 8 pixel characters  Smooth vertical 1 pixel scrolling is completely independent of vertical char size or 1 byte horizontal scrolling.