CPCWiki forum

General Category => Demos => Topic started by: ComSoft6128 on 18:21, 25 March 21

Title: Unexpected Plus effect
Post by: ComSoft6128 on 18:21, 25 March 21
Not a programmer, not a hardware guy, so can anyone explain to me the effect seen at the end of this video?

Small B-Asic demo - 6128 Plus only Irish demo from 1994.


https://www.youtube.com/watch?v=5wFpgyjGJDI (https://www.youtube.com/watch?v=5wFpgyjGJDI)


Links:

https://www.cpc-power.com/index.php?page=detail&num=11651 (https://www.cpc-power.com/index.php?page=detail&num=11651)

https://www.cpc-power.com/index.php?page=staff&lenom=Paul%20GARGAN (https://www.cpc-power.com/index.php?page=staff&lenom=Paul%20GARGAN)

https://www.cpcwiki.eu/index.php/Amstrad_User (https://www.cpcwiki.eu/index.php/Amstrad_User)


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.

Title: Re: Unexpected Plus effect
Post by: eto on 19:25, 25 March 21
What do you mean?
Title: Re: Unexpected Plus effect
Post by: ComSoft6128 on 19:38, 25 March 21
"CPC PLUS" is still shown on the screen/overlays the screen display after a soft reset or when the DES Rom is launched - in fact the only way to remove it is to switch off the Plus. I've never seen that before.
Title: Re: Unexpected Plus effect
Post by: Ygdrazil on 19:41, 25 March 21

Hi There


Do you mean the CPC PLUS sprites still being displayed on the screen!?


The demo does not clean up after it terminates


Plus features are still enabled by the ASIC so sprites still i ASIC memory..


I think!


/Ygdrazil

Quote from: ComSoft6128 on 18:21, 25 March 21
Not a programmer, not a hardware guy, so can anyone explain to me the effect seen at the end of this video?

Small B-Asic demo - 6128 Plus only Irish demo from 1994.


https://www.youtube.com/watch?v=5wFpgyjGJDI (https://www.youtube.com/watch?v=5wFpgyjGJDI)


Links:

https://www.cpc-power.com/index.php?page=detail&num=11651 (https://www.cpc-power.com/index.php?page=detail&num=11651)

https://www.cpc-power.com/index.php?page=staff&lenom=Paul%20GARGAN (https://www.cpc-power.com/index.php?page=staff&lenom=Paul%20GARGAN)

https://www.cpcwiki.eu/index.php/Amstrad_User (https://www.cpcwiki.eu/index.php/Amstrad_User)


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.


Title: Re: Unexpected Plus effect
Post by: ComSoft6128 on 19:44, 25 March 21
Yes the text/sprites are still being displayed but a soft reset doesn't clear them - I thought reset cleared the memory?
Title: Re: Unexpected Plus effect
Post by: Sykobee (Briggsy) on 10:40, 26 March 21
Sprite memory is separate, on the ASIC.


As I don't think they changed the firmware from the original CPC, so the clean up of the sprites and their registers is not happening.
Title: Re: Unexpected Plus effect
Post by: ComSoft6128 on 18:04, 27 March 21
Thanks for the replies/info.


I didn't know the ASIC chip contained memory - 1K/2K or a few bytes?
Title: Re: Unexpected Plus effect
Post by: eto on 18:14, 27 March 21
Quote from: ComSoft6128 on 18:04, 27 March 21
Thanks for the replies/info.


I didn't know the ASIC chip contained memory - 1K/2K or a few bytes?


Probably 4K (16 sprites, 256 Bytes each.)
Title: Re: Unexpected Plus effect
Post by: Skunkfish on 11:14, 28 March 21
Since Plus software was intended to be on cartridge and a soft reset not possible (or if it was, it would boot back into the game), they probably though there was no need to clear the ASIC memory on a soft reset...
Title: Re: Unexpected Plus effect
Post by: Animalgril987 on 17:27, 28 March 21
The ASIC memory is 16k, and is paged into 0x4000 to 0x7fff in the plus memory map when unlocked and then activated.
It not only contains sprite colour information, but also X and y coordinates for each sprite, sprite magnification factor, colour palette, DMA channel data, analogue controller data and more.
Title: Re: Unexpected Plus effect
Post by: roudoudou on 17:36, 28 March 21
Quote from: Sykobee (Briggsy) on 10:40, 26 March 21
As I don't think they changed the firmware from the original CPC, so the clean up of the sprites and their registers is not happening.
mostly because to clean-up Asic, you need to unlock it first and Amstrad did not want to unlock full features at boot => YOU MUST PAY :D
Title: Re: Unexpected Plus effect
Post by: Animalgril987 on 17:50, 28 March 21
I believe the unlock sequence is on the Wiki... :D
Title: Re: Unexpected Plus effect
Post by: ComSoft6128 on 18:12, 28 March 21
Quote from: Animalgril987 on 17:27, 28 March 21
The ASIC memory is 16k, and is paged into 0x4000 to 0x7fff in the plus memory map when unlocked and then activated.
It not only contains sprite colour information, but also X and y coordinates for each sprite, sprite magnification factor, colour palette, DMA channel data, analogue controller data and more.


So just to confirm; this is an extra 16K is on top of the 128K on the 6128 Plus giving a total of 144K?
Title: Re: Unexpected Plus effect
Post by: roudoudou on 18:53, 28 March 21
Quote from: ComSoft6128 on 18:12, 28 March 21

So just to confirm; this is an extra 16K is on top of the 128K on the 6128 Plus giving a total of 144K?
It's not exactly memory, it's a mapping to Asic

there is 4096 half-byte for sprites (only lower nibbles are stored/readable) and a few registers (80 bytes for sprites on a 128 bytes area and a bunch of bytes for INT and DMA)
also some adresses are mirrored in the 16K area
this mapping is done in the #4000-#7FFF area so when Asic is mapped, you cannot access RAM below, you must disable mapping
Title: Re: Unexpected Plus effect
Post by: Animalgril987 on 22:07, 28 March 21
Yes, it's as @roudoudou (https://www.cpcwiki.eu/forum/index.php?action=profile;u=1714) says, I didn't explain too clearly.
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