My A500 doesn´t display image on some demos, why ?

[scannercf]

 recently have bought an Amiga 500, and I found a little problem that i can´t fix out.
 
The computer doesn´t show image when I try to run some demos, while the audio runs perfect (if the machine don´t hang up).
 
This is my Amiga ...
 
Motherboard rev. 5
Agnus 8372a
Eureka 512 in trap door
Supra Drive 500XP with 2 Mb.
1010 disk drive.
1084 monitor connected through RGB cable.
PSU 110v.
 
Sysinfo tells this :
 
DMA/Gfx : ECS Agnus 1 meg.
Mode: PAL
Display: Std. Denise
CPU/Mhz: 68000
FPU: NONE
MMU: N/A
VBR: N/A
Horiz Khz: 15.72
Eclock: Hz: 715909
Ramsey Rev: N/A
Gary Rev: N/A
Card Slot: NO
Vert Hz: 60
Supply Hz: 60
 
I found some there that doesn´t fit the standards ... the processor runs a NTSC speed , the frecuency is the NTSC frec., but the machine is in PAL mode, maybe this is the problem, but I don´t know how to fix it.
 
I you can ... please hel me !!!
 
Thank you very much.
 
 
Claudio

[JetRacer]

Are you 100% certain that these demos are meant to run on the A500 and not the A1200?

Then there's always the possability that the demos won't run on anything else than the specific setup it was developed on (read: lame programmer). There's heaploads of that stuff you know. Demos which only run with 512KB/1024KB/2048KB chipmem, with or without fastram, only works with 1.2/1.3/2.0 kick, won't work with HDD, etc.

Nearly (joke):

...only working 10% of the time and only if run off the programmers own floppy, in the same avr. temperature/moist conditions and by the programmer himself (if ever) :-) :-) :-)

Most sane people use UAE for those.

[Oldsmobile_Mike]

The computer doesn´t show image when I try to run some demos, while the audio runs perfect (if the machine don´t hang up).

Have you tested these same demos on another machine, and seen them work fine?

It may not be related, but I noticed after I switched my A1200 from an '020 with 8Mb fast to an '030 with 4Mb fast that not only did a lot of my old demos run smoother, I also was able to see a lot of additional frames of animation and still pictures that previously were getting dropped.  Note that this isn't a typo - I went from 8Mb fast to 4Mb, but it was the faster processor that made all the difference.

Perhaps the demos you're trying to watch require a faster processor?

FYI, I too have a PAL Amiga.  Every dog-gone time I turn it on, if I want everything to run normally (other than demos or old games, for which I keep it in PAL mode), I've got to change it to NTSC mode in the early startup control.

Good luck,
Mike

[scannercf]

I found the solution !!

I found two little programs incluided into the Kill2090.lha archive in Aminet.
These programs are called "ResetPAL" and "ResetNTSC", what they do is force the 8372a to PAL or NTSC mode, and when I run the "ResetPAL" the machine changes to 50 Hz,  7.09 Mhz 68000 ... and the demos works ok.

Thanks to everybody who tried to help me !!!

Claudio

[lempkee]

hrmmm.. at first it sounded like you had an a500+....now i am just confused...glad u solved your prob.

[Brian]

Hmm... Motherboard Rev5 sounds much like A500 and not A500+ to me. :-D

Hmm.. looking at this it looks like you got a PAL Agnus chip in a NTSC machine... Agnus 8372A is for PAL machines.