Karoshi MSX Community
05 de Julio de 2021, 12:25:25 pm *
Bienvenido(a), Visitante. Por favor, ingresa o regístrate.

Ingresar con nombre de usuario, contraseña y duración de la sesión
Noticias:
 
   Inicio   Ayuda Buscar Ingresar Registrarse  
Páginas: [1]
  Imprimir  
Autor Tema: Myth or Fact: Does invalid PSG IO config harm the MSX?  (Leído 6607 veces)
0 Usuarios y 1 Visitante están viendo este tema.
dvik
Karoshi Fan
**
Mensajes: 80


WWW Email
« : 01 de Abril de 2007, 08:08:52 pm »

I've been discussing the PSG io pins with some people and all are quite skeptic that programming the PSG  IO pins 'wrong' will harm the MSX. To me it doesn't makes sense that programming the IO pins in a different way would do any harm at all. I guess its a tiny chance that it may harm some devices plugged into the joystick port but not that it could damage the MSX.

I think this is a myth that started some time ago and I think its time to either bust the myth or confirm it. Does anyone has any documentation or proof that it can damage the MSX?

Since I don''t beleive in this myth, I think its sad to see the reactions developers get when they don't write these bits 'right'. On the other hand, if it is a real issue, I really want to know.
En línea
jltursan
Karoshi Forum's Guru
*******
Mensajes: 1516


¿Que es lo que has aprendido hoy?


WWW Email
« Respuesta #1 : 02 de Abril de 2007, 02:26:44 pm »

Indeed, IMHO people is overreacting a bit about that. IIRC someone gave here some more details about those PSG bits and the strange behaviour behind them, I don't remember the thread; but he told us that if they're badly initialized, they make the joysticks stop working...and not always. I doesn't care anymore, luckily it's very easy to avoid, just a matter of be careful... Wink

I say: Myth 60% / Fact 40%

 Smiley
En línea

Doom dee doom dee doom
Dioniso
Visitante
« Respuesta #2 : 02 de Abril de 2007, 04:13:46 pm »

The thing is that if there's a little possibility of that to be true we should avoid it. I have played -and keep playing- games that doesn't take that into account and NOTHING has ever happened to any of my MSXs.

The only problem detected so far is that the joystick doesn't work in MSX2+ while %00xxxxx is being written to R7. Someone reported that in this forum.
En línea
GuyveR800
Karoshi Newbie
*
Mensajes: 49


WWW
« Respuesta #3 : 03 de Abril de 2007, 06:59:47 pm »

There are MSX2 machines that hang very hard and need a power cycle to work again (reset doesn't work) when these bits are badly written. Quibus confirmed this with his Sony HB-G900P. That means there is a high possibility a lot of MSX1 machines will have the same reaction, or possibly even one involving smoke.

Just think about it: You're making and input port out of an output (or an output out of an input) and then put 5V on it... What do you think will happen Huh Try driving on the wrong side of the road with your car to find out!

But, regardless of any physical damage:
1. It makes joysticks not work for a lot of machines. (so it's a BUG)
2. It's against the MSX standard.
3. It's so easy to fix...

If you feel sad about programmers getting bad comments, maybe you also feel sad when they don't know how to access the disk properly and format your harddisk by accident? It's the same thing...

Denying this 'myth' is the same as saying it's ok to play with a loaded gun.
En línea

Founder of The New Image in 1991.
Founder of MSX Banzai! in 1997.
BiFiMSX
Karoshi Newbie
*
Mensajes: 23


« Respuesta #4 : 03 de Abril de 2007, 07:11:40 pm »

I can recall a testversion of dvik's Sudoku game which I tried in the Goldstar FC-200 and the joystick worked either partially or not at all, because those bits were set incorrectly. And that machine also has a real PSG.
En línea

boblet
Karoshi Newbie
*
Mensajes: 28


Pressing F9 will enhance your experience


WWW
« Respuesta #5 : 03 de Abril de 2007, 08:21:31 pm »

after a brief talk in the cool irc channel Smiley

set the ports the correct way, or the joysticks don't work, but it probably isn't harmful "generally"

if your msx is setup the way the schematic is in the tech manual, then "no joystick"

if however some are different, as it seems to be from the stuff above with some machines crashing hard, then not setting up r7 in the correct way is a programmer fault, it's meant to be one way only, or else it's wrong, I'd call the joyports being disabled wrong.

maybe someone could put up a list of the machines that completely malfunction and the ones that just have no joyport functionality.

having said all this of course, a machine that stops dead when r7 isn't the way it's meant to be is maybe a borked by design machine Smiley

either way, just set up r7 the happy way and it'll work for everyone

I'm just going off the pictures in the sony msxtech.pdf it shows an actual ay chip connected to actual 74 series chips, msx engine machines may have subtle variations that cause this to vary from inconvenience to badness.

En línea

Or is it?
dvik
Karoshi Fan
**
Mensajes: 80


WWW Email
« Respuesta #6 : 04 de Abril de 2007, 01:19:11 am »

I agree with Guyver, that any application should do the right thing and I also remember now that BiFi found that the joysticks in a beta of the sudoku game didn't work because I used and old version of the pt3 player.

I guess the question is how bad it is to not do it apart from having your game not able to run on some machines.

One interesting thing though. I haven't had a chance to confirm it but I heard some MSX bioses or DOS implementations sets both ports to input as default. I assume this is ok, because a bios would be specifically written for one MSX hardware, right? So if there is no issue on that particular hardware, the bios could do what it wants.
En línea
boblet
Karoshi Newbie
*
Mensajes: 28


Pressing F9 will enhance your experience


WWW
« Respuesta #7 : 04 de Abril de 2007, 09:39:03 am »

if you got both ports as input it'l mean that the then "inputs" on port b would be connected to inputs on the 74 series chips that are directly connected, been given the impression that 's not a harmful situation, but it does mess with my head as being abuse of logic Smiley

other way around feels like bad karma to me but I'm probably just being scared

the machines that stop dead on r7 abuse, all msx engine machines? I take it there's different versions of msx engine maybe there's subtle optimisations and differences that give rise to badness

so I guess it's setup r7 the one true way™ and that's that Cheesy


En línea

Or is it?
GuyveR800
Karoshi Newbie
*
Mensajes: 49


WWW
« Respuesta #8 : 08 de Abril de 2007, 06:34:47 pm »

One interesting thing though. I haven't had a chance to confirm it but I heard some MSX bioses or DOS implementations sets both ports to input as default.
This should be confirmed before speculated upon, IMHO.

What is a fact tho, is that at least one of the MSX-ENGINE chips (I forgot which) with integrated PSG (btw probably all with YM2149 and not AY-3-8910) does not care about these bits at all. It makes sense for a MSX-specific chip to remove the functionality of these bits if the standard already specifies them they should remain in a certain configuration.
En línea

Founder of The New Image in 1991.
Founder of MSX Banzai! in 1997.
boblet
Karoshi Newbie
*
Mensajes: 28


Pressing F9 will enhance your experience


WWW
« Respuesta #9 : 08 de Abril de 2007, 11:30:58 pm »

that makes a lot of sense actually, as you aren't supposed to alter them from what they are meant to be, trying to do anything to them would be meaningless in this case

I guess it's just one of those subtle design things that requires doing things in a particular way due to the design

er, if that makes any sense
En línea

Or is it?
jltursan
Karoshi Forum's Guru
*******
Mensajes: 1516


¿Que es lo que has aprendido hoy?


WWW Email
« Respuesta #10 : 09 de Abril de 2007, 09:15:36 am »

Indeed it makes sense... Wink
En línea

Doom dee doom dee doom
Páginas: [1]
  Imprimir  
 
Ir a:  

Impulsado por MySQL Impulsado por PHP Powered by SMF 1.1.21 | SMF © 2013, Simple Machines XHTML 1.0 válido! CSS válido!