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#1

Programming / Re: interesting walkthrough vi...

Last post by McArti0 - Today at 06:13

OUTI   ;5
INC B ;1
NOP   ;1
NOP   ;1

1000/8=125kHz

#2

Programming / Re: interesting walkthrough vi...

Last post by lightforce6128 - Today at 00:55

In our Wiki I found this additional information about the sound chip AY-3-8912:

1) There are four different known versions of the chip used for the CPC. Maybe these versions behave differently, maybe not.

2) Internally the chip works with 125 kHz. This means even if its registers are updated with 166 kHz, it will nevertheless only update the volume with 125 kHz.

3) There are no additional control lines on the chip to acknowledge or synchronize with something. This means: If the chip is programmed to read in register values written by the CPU through the PPI (BDIR=1, B1=0), it will do this non-stop. The PPI will remember the last written value and keep it available (latch). What is not clear is if the PSG stops normal operation as long as registers are written. From my observation: It does not care and simply continues its normal work. This means: One can change register values (e.g. the volume level) during operation without altering the mode. This saves two OUT commands per sample.

4) Only the envelope shape register (#0D) somehow recognizes writing and restarts the envelope.

#3

Programming / Re: interesting walkthrough vi...

Last post by lightforce6128 - Yesterday at 23:41

We can send samples at 166 kHz. Should be enough ...

Is this supposed to be some kind of competition for the retro-computer sample-replay world-record?

you didn't take dithering into account

Dithering? ... Yes that is exactly what I had in mind: Dithering ...

No In fact I remembered a glorious article about high-end sound with the C64 at 48 kHz (and a big bunch of memory). So yes, I had some kind of competition in mind. Also you are absolutely right: Everything above 44 kHz will not be audible.

What brings us back to dithering: The idea of dithering is to mix a signal with a low resolution (e.g. 1 bit or 4 bit) with noise that will push the single samples sometimes below and sometimes above the bit levels. With this the resolution can be enhanced greatly, lowering or even removing noise artifacts caused by the low resolution.

But the dithering noise itself is added. Although this is a neutral sound, it nevertheless is clearly audible - except you push it above the 16 kHz level. With 44 kHz there is not much room to do this, but with 166 kHz there is. With this, the audio resolution can be increased, noise artifacts can be reduced, and the dithering noise maybe can be lowered until it gets inaudible.

However, professional equipment uses frequencies of more than 1 MHz for this trick.

#4

Programming / Re: interesting walkthrough vi...

Last post by MaV - Yesterday at 22:56

"CPC Meuuuuhting"

That one?

#5

General Discussion - Introductions / Re: FUN FACT: Amstrad was the ...

Last post by GUNHED - Yesterday at 22:27

Its great Multitasking OS

No, in Rosanne there is no multitasking at all. There is not even "multi-programming".

As soon as you go back from the current program it has to store its document and shut down itself again before you can do anything else. When returning from a program and switch to another one, which was already running before it lost all its states and needs again to load an existing document or start a new one.

The UI concept is similiar to the NC100/200, nice designed, lot of easy to use keyboard shortcuts.
But Rosannes display routines are just terrible slow. The screen is 38K, but the CPU is 4x as fast as these of the CPC and NC, and you can watch, how it is plotting things from up to down line by line.
Maybe some like this because it gives some retro feelings, but with a 16MHz Z80 you can expect a lot more.

Oh, thanks for the information. My informations were different. But one can learn every day something new.

Hot candidate for a SymbOS port I would guess... 

#6

Programming / Re: interesting walkthrough vi...

Last post by McArti0 - Yesterday at 22:24

No. Writing to register F6 is completely unnecessary.

Really?
Would be funny, if we were all wrong in the past.

Code Select Expand

org #4000

di
call init

ld d,#F5
ld bc,#F400

loop

  inc c
  out (c),c

vsync1
ld a,d : in a,(0) : rra : jr nc,vsync1
vsync2
ld a,d : in a,(0) : rra : jr c,vsync2

jr loop

ret

init
ld bc,#F782 ;PC set PA as OUT
OUT (c),c

ld bc,#F407 ;PA has R sel (vol A channel)
OUT (c),c

ld bc,#F6C0 ;PC move PA to sel R
OUT (c),c

ld bc,#F600 ;PC dis AY
OUT (c),c

ld bc,#F43e ;PA set
OUT (c),c

ld bc,#F680 ;PC open AY and connect PA with Rsel
OUT (c),c

ld bc,#F600 ;PC dis AY
OUT (c),c

; R8

ld bc,#F408 ;PA has R sel (vol A channel)
OUT (c),c

ld bc,#F6C0 ;PC move PA to sel R
OUT (c),c

ld bc,#F600 ;PC dis AY
OUT (c),c

ld bc,#F409 ;PA set
OUT (c),c

ld bc,#F680 ;PC open AY and connect PA with Rsel
OUT (c),c

ld bc,#F600 ;PC dis AY
OUT (c),c

; R0

ld bc,#F400 ;PA has R sel (vol A channel)
OUT (c),c

ld bc,#F6C0 ;PC move PA to sel R
OUT (c),c

ld bc,#F600 ;PC dis AY
OUT (c),c

ld bc,#F400 ;PA set 0
OUT (c),c

ld bc,#F680 ;PC open AY and connect PA with Rsel
OUT (c),c



ret

#7

General Discussion - Introductions / Re: FUN FACT: Amstrad was the ...

Last post by BSC - Yesterday at 21:21

After doing some more research, I found the PCW16 to be an excellent machine! (Despite the slowness while drawing the graphics, lack of Internet connection, etc.):

- A color monitor was not really needed for those purposes
- A hard drive was not necessary because files were 7KB and you could store hundreds of those in a 1.4MB floppy
- The machine could even start itself to remind you of some appointment!
- The UI is fantastic and perfect for non-IT people
- The system could backup itself in just a few minutes in a floppy disk
- The thing looks gorgeous

The thing also looks like a belated Macintosh clone. But anyhow thanks for the post, I was not aware of this machine.

#8

Emulators / Re: CPCEmu v3.0 (April 2025)

Last post by ikerkaz - Yesterday at 21:05

The numeric keyboard works like a joystick or not, depending of the NUMLOCK status.

This is the way it should work.

What brand/type of keyboard do you have? Perhaps I find a similar one to test here.

Keyboard: Logitech K375s (bluetooth)
Mouse: Logitech M720 (bluetooth)

Also I tried with keyboard & mouse pack Logitech MK270 (separately keyboard is model K270 and mouse is M185) with an USB receiver (not bluetooth).

#9

T

Applications (CPC and CPC-related) / CPC6128 - CP/M System Disks

Last post by tubs74 - Yesterday at 20:59

Hi, 

I wonder if anyone can shed some light - I've bought some system disks (3 sets), 

Set 1 - Purple (Amsoft), Side 1 CP/M System/Utilities, Side 2 Programming Utilities, Side 3 Dr Logo and Help, Side 4 CPM2.2 (no copright dates)
Set 2 - Aqua (Amsoft), Side 1 Loco Script Word Processor, Side 2 CP/M Plus, Side 3 Programming Utilities, Side 4, Dr Logo and Help (no copyright dates)
Set 3 (only 1 disk) Burgundy (Amstrad PLC) System/Utilities/Basic CP/M Plus - Copyright DR and Amstrad 85, 86, 87

Set 1, will boot from my CPC6128, and I can browse the files/run commands etc, so these are CPC6128 disks.
Set 2, from Amstrad basic on 6128 I can "cat" the disks, and get a listing.  Trying :cpm, i get retry, cancel, Ignore.  If I use the bootable CPM above and swap disks, I cannot do a DIR as I get retry/cancel/ignore.  I'm assuming maybe Aqua disks are PCW 8256/8512 disks
Set 3 (which is only one disk) won't cat from basic, and won't dir in CPM.  I'm assuming these are maybe the PCW9512?

Onto CP/M on the 6128, it boots with 61k available - on my spectrum +3 and C/PM I then have an M drive, that is the rest of the RAM - does CP/M on the 6128 have full access to 128k of RAM in a similar way?

Is there anyway to read the Aqua disks on the 6128, so I could look at loco script for example.

Was the CP/M+ the only version of CP/M available for the 6128, I'm assuming so as it's te last 8bit version, but I wonder if there were any imrovementys to CP/M Plus, that can be rolled back to the original CP/M plus that comes with the 6128?

#10

News & Events / Re: CPC Scene Radio!

Last post by Targhan - Yesterday at 20:17

Hi all, the CPC Scene Radio is currently down due to a strange "upgrade" from asuraCast. I'll try to repair it very soon!