who, of you here have a foot in both the a8 and c64 camps

[ijor]

My guess is: POKEY volume is a DAC which controls an amplifier transistor directly. in DAC-mode the volume register simply amplifies a constant voltage while in normal mode it amplifies the waveforms.

 

My guess is that it's like the NES audio.

 

I don't know why you are both guessing, when this is fully and clearly documented. There is a very nice logic diagram in the "official" Atari Hardware Manual (available in this forum), next to the board schematics. I was going to detail it here, but I am (a bit) lazy. Just ask if you can't find it or something is not clear.

 

Only note that this describes the Pokey output, not the computer audio output.

[Bryan]

A little more info: Pokey's audio simply acts as a voltage divider in the chip. Each channel has 4 resistors to ground that are either connected or disconnected from the output. A single 1K pull-up resistor provides the path to 5V. You can calculate the output voltage by combining all the "in-use" resistors inside Pokey with the external 1K. Right at the audio pin, the output should look a lot like a square wave, but with an average DC level that drops with each added voice (new set of pull-down resistors in use). This is the drawback to using a single pin with all channels connected. To keep the DC level more constant, you can set unused channels to a fixed voltage level rather than turning them off (VOL=0).

 

Anyway, the signal goes into a buffer stage and passes through a capacitor on the way in and out. This is most likely where the strange wave shape comes from. Atari implemented a high-pass amplifier that rolls off the low end of the frequency spectrum and removes the DC artifacts of Pokey to a degree.

[atariksi]

This was sort of an interesting thread before. Why couldn't you guys have started a new thread for all this tech stuff?

 

Feel free to continue with the topic; some prefer the "o" in "who" to a "y":

 

why, of you here have a foot in both the a8 and c64 camps

 

It could easily be misread if we had two long topic names that only differed by one letter.

 

So, aside of attacking other users personally, you even lack basic reading abilities?

 

 

Thorsten

 

You're describing yourself. You just did a personal attack and misread what I wrote. You previously also replied without addressing the points that I made (probably never read what I wrote nor the thread). It's better for you to NOT read what I write then to misread it. You can't distinguish between the truth and an personal attack if you think anything I stated here is a personal attack. Cowards just come and blurt out whatever comes on the top of their head without addressing the points that are being made. And you are attacking a light humor message not even the guts of the issue. I know the truth hurts and you just have to try to find some fault even if you have to misinterpret/misread things.

 

So you are stating that whatever you have read from AtariKSI here is a personal attack. First you falsely declare people to be wrong and now claim they are personal attacks because you can't deal with it rationally. Sorry, I deal with rationality not blind following nor accepting anyone trying to bully others. You can go try bullying someone else. You yourself made your first post that was off topic (talk about hypocrites).

 

There's no insults, personal attacks, nor misread things in this message so read carefully before blurting out whatever comes up on the top of your head.

[atariksi]

If you look at an oscilloscope or sound card sampling...

 

Normal "square" waves aren't as such. You have a near instantaneous "attack" as you would with a normal square/pulse.

Then, a decay back towards zero, which begins steeply and flattens out.

 

Then repeat with reverse-phase for the remainder of the cycle.

 

|\
|  \ 
|	\
|	  -   
	 |	   -
	 |	 /
	 |  /
	 |/

 

Not a great illustration, but kinda close... I can put a proper pic up later.

 

What's the time scale on this drawing and what instructions does it represent on Atari end?

[Rybags]

That's just the general shape of a pure tone...

 

Getting the 'scope out again...

 

 

That's using Audf1=$A0 Audc1=$A8

 

The picture didn't show the vertical lines, so I added them back in.

Edited March 2, 2009 by Rybags

[atariksi]

That's just the general shape of a pure tone...

 

Getting the 'scope out again...

 

 

That's using Audf1=$A0 Audc1=$A8

 

The picture didn't show the vertical lines, so I added them back in.

 

I was interested in something like the following as seen on a scope (don't have a scope currently and soundblaster is limited to 48Khz):

 

LDA #0

STA 54272

STA 54286

LDX #240

LDY #241

NxtInbetwen:

STA 54282 ;WSYNC (to avoid refresh interference)

STX 53761

STY 53761

INX

INY

BNE NxtInbetween

[TheRogue]

Hi, I'd like to add that I have my foot in both the Atari and Commodore camps, as well as many others. I just got into the Atari 8 bit recently, but am diving in fast. My collection is as follows:

 

Ataris

 

Atari 400

Atari XEGS (S-Video, Internal MyIDE, Internal SIO-2-PC, Inovative 128k RAM, Atari 1050 with Happy upgrade, Atari 1027)

Atari 1040 STf

Atari 1040 STe(SC1224 Color monitor, SM124 Monochrome monitor, MegaFile-30 HD, 4 Megs RAM, SatanDisk SD card reader)

 

Commodores

VIC-20

C-64

C-128 (1541, 1571 (Both with parallel ports for use with X1541 PC cable), will be buying IDE interface when new run of boards is done)

Amiga 2000 (68030 33 MHz Accelerator, 16 MB ram, SCSI controller with 2 gig HD and CD-R, OS 3.5)

Amiga 1200

Amiga CD32

 

Apple

Apple II+

Apple IIe Enhanced (128k RAM, 80 column card, Mouse card w/ PS/2 Mouse adapter, 2400 Baud modem, Disk ][ card w/ 2 drives)

Apple IIgs ROM1 (SiriusRAM 8MB RAM expansion, Grappler+ Parallel printer card, IIgs 800k 3-1/2 inch drive, BlueDisk card with 1.44 MB MFM floppy, MicroDrive/Turbo DMA IDE card w/ IDE-to-CF adapter and 256 meg CF card, Uther Ethernet Card)

Macintosh +

 

CoCo

CoCo 1

CoCo 2

CoCo 3

 

Others

 

Yamaha CX5MII-128 MSX

Texas Instruments TI99/4A

SAM Coupe ROM3 (512k RAM, FDD interface, PS/2 Keyboard interface, Quazar Surround soundcard, Quazar Surround sampler module, Trinity Ethernet/SD interface, Serial Mouse Interface, SID chip interface)

Symbolics XL1200 LISP machine (8 MWords RAM, 9GB SCSI HD loaded with Symbolics software, sources, and docs, CD-ROM drive, 19" Monochrome Console display with Keyboard and 3 button mouse)

 

I think that's just about it, but if I think of anything that I forgot I'll edit the post.

 

I've been collecting for many years now, it's my passion. Any old computers, I just have to have them.

[Thorsten Günther]

I've been collecting for many years now, it's my passion. Any old computers, I just have to have them.

 

Thank you for turning the thread back on topic. I consider my main problem that I don''t have the space or time even for my Ataris, much less for other computers (though I'd want an Amiga 600, C64-II and several of the more exotic computers like the Commodore C116, Enterprise 128, Oric Atmos, Sharp X1, Sinclair Spectrum 128K, etc., if only I could find the aspace to store them properly).

 

Thorsten

[carmel_andrews]

well i did have a couple of amiga's (a 600 and 1200, the 1200 came with aq puny HD) now that people mention that

 

i also had, back in the day various speccy's, from the speccy 16k right upto the plus 2 (though apparently there were different versions of the plus 2) an amstrad 464 (tape version) with yucky green screen monitor a beeb micro (loaned from the repair shop while they were butchering my speccy) and some non descript flavour of MSX

[FastRobPlus]

Those are nice collections.

I mainly have A8 systems now. I don't really want any of them other than the 800, which I hope to upgrade with Warerat's magic XL upgrade when available.

For Commodore I do have an SX-64 for all-in-one gaming. I really wish there were an all-in-one (monitor, drive, keyboard) A8 system!

 

I do have one humble Amiga 1000. It's modestly upgraded with a rejuvenator, a Byte by Byte PAL JR Zorro bus, an AT Once 286 card, A PP&S 68040 25Mhz accelerator with 8MB FastRAM, audio upgrades, full ECS chipset, CD-RW, Deneb USB, 2MB chip RAM, Flicker Fixer and multiscan monitor, and a few other things. But mostly it's stock.

[atariksi]

I've been collecting for many years now, it's my passion. Any old computers, I just have to have them.

 

Thank you for turning the thread back on topic.

...

 

Which posts did you make that were off topic: "Replying to who, of you here have a foot in both the *A8* and *C64* camps"?

 

>I consider my main problem that I don''t have the space or time even for my Ataris, much less for other computers (though I'd want an Amiga 600, C64-II and several of the more exotic computers like the Commodore C116, Enterprise 128, Oric Atmos, Sharp X1, Sinclair Spectrum 128K, etc., if only I could find the aspace to store them properly).

 

>Thorsten

 

Here's where you are wrong again. You have a PC running at 1Ghz+ sitting in your living room so you have more space for "other computers". Remember, that your PC (and most others') are made of off-the-shelf chips and are inferior. The topic asked for A8 and C64 camps not all your other interests. Besides posting things off topic, you don't know English-- there's no such word as aspace. That may mean anti-space in your mind but not in mine. And some of the models you mentioned equal out with others so there's no need to mention them.

[Thorsten Günther]

Those are nice collections.

I mainly have A8 systems now. I don't really want any of them other than the 800, which I hope to upgrade with Warerat's magic XL upgrade when available.

 

Uh, I wouldn't dare doing this to my PAL 800 - these are much too rare IMHO. An XL on the other hand is a very common machine.

 

For Commodore I do have an SX-64 for all-in-one gaming. I really wish there were an all-in-one (monitor, drive, keyboard) A8 system!

Yep, although there was a 65XEP (P for portable) with a green monochrome monitor on the 1985 CES, this machine sadly only exists as a prototype. The SX-64 is another very nice rarity along with the Amiga 1000 you also own.

 

I do have one humble Amiga 1000. It's modestly upgraded with a rejuvenator, a Byte by Byte PAL JR Zorro bus, an AT Once 286 card, A PP&S 68040 25Mhz accelerator with 8MB FastRAM, audio upgrades, full ECS chipset, CD-RW, Deneb USB, 2MB chip RAM, Flicker Fixer and multiscan monitor, and a few other things. But mostly it's stock.

 

Err, which part of it exactly is stock?

 

 

Thorsten

[carmel_andrews]

Those are nice collections.

I mainly have A8 systems now. I don't really want any of them other than the 800, which I hope to upgrade with Warerat's magic XL upgrade when available.

For Commodore I do have an SX-64 for all-in-one gaming. I really wish there were an all-in-one (monitor, drive, keyboard) A8 system!

 

I do have one humble Amiga 1000. It's modestly upgraded with a rejuvenator, a Byte by Byte PAL JR Zorro bus, an AT Once 286 card, A PP&S 68040 25Mhz accelerator with 8MB FastRAM, audio upgrades, full ECS chipset, CD-RW, Deneb USB, 2MB chip RAM, Flicker Fixer and multiscan monitor, and a few other things. But mostly it's stock.

 

 

 

 

 

I didn't now you could upgrade the A1000 with full ECS support, i thought that C/S was only designed for the A500plus and the A600 (i liked the a600, it was smaller)

Edited March 14, 2009 by carmel_andrews

[FastRobPlus]

Yeah I would love the XEP - or a good copy of one. I'd keep the SX-64 and the XEP as my primary Commodore and Atari.

[Thorsten Günther]

Yeah I would love the XEP - or a good copy of one. I'd keep the SX-64 and the XEP as my primary Commodore and Atari.

 

Beetle's 1500XL laptop is even nicer, but rumour has it that he even turned down a EUR 2,000 offer for it.

 

Is it correct that the SX-64 is not 100% compatible with the C64 due to the changes in ROM? Do these affect any software at all?

 

 

 

Thorsten

[FastRobPlus]

Yeah I would love the XEP - or a good copy of one. I'd keep the SX-64 and the XEP as my primary Commodore and Atari.

 

Beetle's 1500XL laptop is even nicer, but rumour has it that he even turned down a EUR 2,000 offer for it.

 

Is it correct that the SX-64 is not 100% compatible with the C64 due to the changes in ROM? Do these affect any software at all?

 

 

 

Thorsten

 

Beetle's laptop is amazing, but since I primarily collect boxed software, it would not be too useful to me (It has no built in FDDs or Cassette drive)

 

I'm not an expert on SX-64 compatibility, but I think the cart port sometimes cannot power some devices, and I know the FDD is the crap 1541 mechanism that needs constant alignment. This really limits the SX as a collectible since its high maintenance.

[atariksi]

Yeah I would love the XEP - or a good copy of one. I'd keep the SX-64 and the XEP as my primary Commodore and Atari.

 

Beetle's 1500XL laptop is even nicer, but rumour has it that he even turned down a EUR 2,000 offer for it.

 

Is it correct that the SX-64 is not 100% compatible with the C64 due to the changes in ROM? Do these affect any software at all?

 

 

 

Thorsten

 

Beetle's laptop is amazing, but since I primarily collect boxed software, it would not be too useful to me (It has no built in FDDs or Cassette drive)

 

I'm not an expert on SX-64 compatibility, but I think the cart port sometimes cannot power some devices, and I know the FDD is the crap 1541 mechanism that needs constant alignment. This really limits the SX as a collectible since its high maintenance.

 

Just use a battery operated 1050 drive.

 

Recently someone gave me a SX-64 (for shipping costs); the CRT does not work. Know any replacement part for it-- perhaps a flat screen?

[FastRobPlus]

Yeah I would love the XEP - or a good copy of one. I'd keep the SX-64 and the XEP as my primary Commodore and Atari.

 

Beetle's 1500XL laptop is even nicer, but rumour has it that he even turned down a EUR 2,000 offer for it.

 

Is it correct that the SX-64 is not 100% compatible with the C64 due to the changes in ROM? Do these affect any software at all?

 

 

 

Thorsten

 

Beetle's laptop is amazing, but since I primarily collect boxed software, it would not be too useful to me (It has no built in FDDs or Cassette drive)

 

I'm not an expert on SX-64 compatibility, but I think the cart port sometimes cannot power some devices, and I know the FDD is the crap 1541 mechanism that needs constant alignment. This really limits the SX as a collectible since its high maintenance.

 

Just use a battery operated 1050 drive.

 

Recently someone gave me a SX-64 (for shipping costs); the CRT does not work. Know any replacement part for it-- perhaps a flat screen?

 

Can't remember how the SX64 screen connects internally. I *think* it's a Y/C or S-VIDEO custom cable. If so, it would be very easy to hack an LCD screen to the unit. I'm sure there are plenty of places to pull the voltage from.

[TMR]

Is it correct that the SX-64 is not 100% compatible with the C64 due to the changes in ROM? Do these affect any software at all?

 

If memory serves, the changes to the ROM remove tape operations (there are no hardware lines for a tape deck on the SX) and re-route the shift and run/stop key combination to boot off disk; as long as code uses the official Kernel calls it should be fine, i've not found anything that broke on my SX64 because the code was being naughty about calling directly rather than using the documented entry points.

 

The only issue i've had is the one that someone else mentioned, when i have an Action Replay connected i only get a limited amount of time before the machine needs to be powered down to "rest".

[atariksi]

Yeah I would love the XEP - or a good copy of one. I'd keep the SX-64 and the XEP as my primary Commodore and Atari.

 

Beetle's 1500XL laptop is even nicer, but rumour has it that he even turned down a EUR 2,000 offer for it.

 

Is it correct that the SX-64 is not 100% compatible with the C64 due to the changes in ROM? Do these affect any software at all?

 

 

 

Thorsten

 

Beetle's laptop is amazing, but since I primarily collect boxed software, it would not be too useful to me (It has no built in FDDs or Cassette drive)

 

I'm not an expert on SX-64 compatibility, but I think the cart port sometimes cannot power some devices, and I know the FDD is the crap 1541 mechanism that needs constant alignment. This really limits the SX as a collectible since its high maintenance.

 

Just use a battery operated 1050 drive.

 

Recently someone gave me a SX-64 (for shipping costs); the CRT does not work. Know any replacement part for it-- perhaps a flat screen?

 

Can't remember how the SX64 screen connects internally. I *think* it's a Y/C or S-VIDEO custom cable. If so, it would be very easy to hack an LCD screen to the unit. I'm sure there are plenty of places to pull the voltage from.

 

Perhaps, it's the power supply related stuff that's preventing the CRT from functioning. Don't want to spend much time so I thought perhaps, there's just a replacement CRT w/power supply.