Amiga 500+ Pal or NTSC?

[Dropcheck]

I think I got flumoxed.

I saw a 500+ which claimed to have the elusive 2meg Agnus chip in it on Ebay and decided to buy it. Now after pulling the cover off I find that the chip in question is actually the Pal version. Now I think I know why there was no power supply with the auction.

What makes a PAL version of the 500+? Is there a set of chips/crystals that I can look for to tell which version I have?

Would a Pal version work just as well in a NTSC A500+?

I hesitate to power it up with the NTSC power supply I have till I know I won't blow it.

[alexh]

Originally Posted by Dropcheck

What makes a PAL version of the 500+? Is there a set of chips/crystals that I can look for to tell which version I have?

If the Agnus is an 8375 : 318069-10 it is PAL and if it has 318069-11 it is NTSC. If you want a second thing to look for (just in case the chip has been replaced) then look for the OSC crystal in the centre of the board. PAL it will be 28.37516MHz and NTSC it will be 28.63636 MHz

Originally Posted by Dropcheck

Would a Pal version work just as well in a NTSC A500+?

Almost certainly not. It won't blow up, but it won't work properly.

Originally Posted by Dropcheck

I hesitate to power it up with the NTSC power supply I have till I know I won't blow it.

No such thing as an 'NTSC power' supply. I presume you mean a 110v 60Hz AC PSU. All Amiga external power supplies have the same DC output (voltage level wise) regardless of the AC input. A 110v Amiga PSU will work fine with a PAL Amiga. You won't blow anything up. Your problem will be that won't be able to connect it to an NTSC TV and get a picture.

[rkauer]

In worst case the PAL Amiga will show a black & white image, even using a NTSC A520.

On an Amiga RGB monitor (like the 1084S) you'll not have any problem, whatsoever.

[Dropcheck]

Hi,

Thanks for your quick reply. It looks like I got taken. All I have is a NTSC A520 to run the signal to my flat screen monitor. Well hopefully the seller owns up and doesn't make me go to ebay dispute. The auction was on the US Ebay site with a US address. The assumption would be that the machine would work with NTSC tvs or monitors unless otherwise specified. The seller didn't.

Next time I'll be smarter.

[thgill]

Personally, I think you are better off with the PAL model. Better compatibility with Demos and Games.

Track down a 1084 monitor as rkauer suggested and you will be good to go.


Unless you absolutely have to run it on a TV, the PAL model is gonna be better in the long run. There are some TVs in the US that can sync to 50 Hz. Many Vizio flat panel TVs will work just fine via composite or s-video from a PAL Amiga.

But you would need to dump the NTSC A520 as it wouldn't work to well with the PAL Amiga. Either purchase a PAL A520, or a far better choice would be one of the PAL/NTSC switchable video encoders that Nathan @ Amigamaniac sells:

http://www.amigamaniac.com/RGB_to_PAL_NTSC_adapter.html


edit: Plus it being an A500+ should have been a clue that there is a good chance its a euro model. I don't know any hard numbers, but NTSC A500+ machines are fairly rare. Kinda like NTSC A600s....they just didn't sell a lot of them here. But boatloads of them in EU.

[rkauer]

Funny thing is my country is an "almost" NTSC land! But ALL my Amigas are European-PAL converted due the fact that you can't find NTSC games & software.

Beside that, the PAL Amiga(s) runs a bit faster than NTSC.

[cosmicfrog]

tis the other way round ntsc runs a bit faster than pal
60 Hz Ntsc to Pals 50Hz

[Dropcheck]

I was planning to upgrade the cpu to the Mega Midget Racer Accelerator with the extra ram board. I know it wasn't the best accelerator for the 500 but it's what I've been able to come up with.

Would it work assuming I could find some way to convert the PAL output to NTSC?

[Dropcheck]

Originally Posted by rkauer

Funny thing is my country is an "almost" NTSC land! But ALL my Amigas are European-PAL converted due the fact that you can't find NTSC games & software.

Beside that, the PAL Amiga(s) runs a bit faster than NTSC.

I have a Mega Midget Racer with a ram board I was planning on putting in it. I know there's a crystal on it for the accelerator cpu. Would the MMR work in a PAL machine? Is it just the video out that is different frequency.

[Sune Salminen]

Originally Posted by cosmicfrog

tis the other way round ntsc runs a bit faster than pal 60 Hz Ntsc to Pals 50Hz

That's exactly what makes the NTSC Amiga slower.

[rkauer]

Originally Posted by Dropcheck

I have a Mega Midget Racer with a ram board I was planning on putting in it. I know there's a crystal on it for the accelerator cpu. Would the MMR work in a PAL machine? Is it just the video out that is different frequency.

The MMR is an accelerator, so it is "universal" for the A500/A2000. PAL or NTSC does not matter.

[Hewitson]

Originally Posted by Sune Salminen

That's exactly what makes the NTSC Amiga slower.

The faster video timing means the CPU must be clocked higher.

I fail to see your logic in this. No one has ever clocked a CPU slower for NTSC mode.

[Sune Salminen]

Is the CPU clocked higher on a NTSC Amiga?

Edit hmm, right, A1000/A500 CPU was clocked ~0.7 Mhz higher, wow!

[Schoenfeld]

Hmm.. some misinformation in this thread.

The A500+ has the ECS chipset, which means it's software-switchable between PAL and NTSC, so all games will work right if they don't fiddle with the NTSC/PAL bit in the chip registers. Unfortunately, some older games do.

Connecting to a video monitor is a different story. If you only own a video monitor, then the colour carrier frequency is critical. The whole Amiga chipset was designed around the NTSC video standard, and therefore the clock rate has been chosen to be 28.63636MHz for NTSC. This divides down to the proper 3.579545MHz for the NTSC colour carrier. If an NTSC machine is software-set to PAL, then this colour carrier still remains the same, so if the monitor can handle the different number of lines of the PAL picture, you'll still have color.

PAL machines came later. The PAL system was kind-of hacked into the Amiga chipset: They somehow had to come up with a clocking scheme that allowed syncronous generation of the PAL colour carrier, without compromising the rest of the chipset too much. The PAL colour carrier is about 1.25 times higher than the NTSC colour carrier. This numer is sufficient enough to create a circuit that generates the right frequency from something that's timed almost like the original Amiga NTSC timing:

PAL colour carrier is 4.43361875MHz. Divide this by 1.25, and you get 3.546895. This is the "new" chipset clock CCK (also known as "colour clock"). Multiply this by 8 and you get the crystal frequency of the PAL model of 28.37516MHz.

Multiply the CCK by two, and you get the CPU frequency of 7.09379MHz - as opposed to the NTSC CPU frequency of 7.15909MHz. This shows that the CPU of the NTSC version is clocked almost 1% faster. Further, the NTSC video system has less video lines, but comparable syncing periods, giving a higher sync time vs. picture time rate, essentially lowering memory performance requirements. This should give another tiny performance boost, because memory is statistically free for more CPU cycles than video cycles (that's in systems without fastmem).

Conclusion:
You will need the right crystal frequency to operate the Amiga on a video monitor, but you will not have to exchange the Agnus chip. Only if you want your system to *cold*start* in your desired mode, changing the Agnus is required.

AmigaManiac's video converter may give you a colour picture on a video monitor even if you have the wrong crystal in the computer. However, his colour clock is NOT in sync with the rest of the chipset. This is bad design practise, as it'll produce constantly moving interference of the colour carrier on the picture. Both the NTSC and PAL video system were designed to get around such interference by syncing the colour carrier with the HSync signal, and the Amiga chipset is making good use of it. I'd suggest to look for an A520 of the right video system, and have the correct crystal frequency in your Amiga - this will give the best possible picture, one that's worthy of an Amiga.

Jens

[TjLaZer]

Originally Posted by Dropcheck

Hi,

Thanks for your quick reply. It looks like I got taken. All I have is a NTSC A520 to run the signal to my flat screen monitor. Well hopefully the seller owns up and doesn't make me go to ebay dispute. The auction was on the US Ebay site with a US address. The assumption would be that the machine would work with NTSC tvs or monitors unless otherwise specified. The seller didn't.

Next time I'll be smarter.

Well wonder what ended up happening with this? Did you get a refund or keep the A500+? The A500+ is very rare in NTSC form. I have never seen one, but PAL versions are very common. I guess the seller should of said it was PAL and you should of known better to ask... I would of just kept it as PAL as you can still use it just fine with a proper monitor or just switch in to NTSC in software. Install Kickstart 3.1 and be done with it. Hopefully you kept it as its a rare machine. If you still have it and want to sell it let me know, looking for one but don't want to have it shipped from Europe!

[ChrisUnionNJ]

You got to luv old threads here's some info about the 500+...

http://en.wikipedia.org/wiki/Amiga_500_Plus

[TjLaZer]

Well it seems the NTSC A500 Plus is extremely rare as it was never released in NTSC countries like USA/Canada. I want to get one and keep it PAL. But shipping would kill the deal and the dreaded leaking battery has all but destroyed almost all of them.

[rkauer]

Incorrect: A600 was mounted in Brazil and here they simply did a transcodification on the unit NTSC signal with PAL colour encoding.

We have several units laying around and it is the most common Amiga in Brazil. Reversing the transcodification is not hard at all and you'll just have to ditch the RF modulator.

[mc6809e]

Originally Posted by cosmicfrog

tis the other way round ntsc runs a bit faster than pal
60 Hz Ntsc to Pals 50Hz

Whether or not NTSC is faster than PAL depends largely on the number of scanlines being displayed, blitter usage, and on the sequence of 68000 instructions being executed.

A PAL system displaying 200 scanlines is often faster than an NTSC system displaying 200 scanlines because the blitter/CPU has more opportunities to touch chipram without interference from bitplane DMA.

A 320x200 bitplane memory clear using a combination of the blitter and CPU will be slightly faster on a PAL system than on an NTSC system, for example, and a memory to memory copy with the blitter is about 6% faster.

Even for pure CPU codes there are cases where a PAL system beats an NTSC system even thought the CPU in the NTSC system is clocked higher.

Try running a long instruction sequence of nothing but CLR.L D0 instructions on both a PAL system and an NTSC system, both displaying 200 scan lines. The PAL system will be faster.

On the other hand, code with a large number of MULs and DIVs will likely run more quickly on NTSC since the CPU spends a lot of time with internal processing.

If the number of scanlines is increased to 256, PAL is often slower when compared to an NTSC system displaying 200 scanlines.

[dJOS]

Originally Posted by Schoenfeld

Hmm.. some misinformation in this thread.

The A500+ has the ECS chipset, which means it's software-switchable between PAL and NTSC, so all games will work right if they don't fiddle with the NTSC/PAL bit in the chip registers. Unfortunately, some older games do.

Connecting to a video monitor is a different story. If you only own a video monitor, then the colour carrier frequency is critical. The whole Amiga chipset was designed around the NTSC video standard, and therefore the clock rate has been chosen to be 28.63636MHz for NTSC. This divides down to the proper 3.579545MHz for the NTSC colour carrier. If an NTSC machine is software-set to PAL, then this colour carrier still remains the same, so if the monitor can handle the different number of lines of the PAL picture, you'll still have color.

PAL machines came later. The PAL system was kind-of hacked into the Amiga chipset: They somehow had to come up with a clocking scheme that allowed syncronous generation of the PAL colour carrier, without compromising the rest of the chipset too much. The PAL colour carrier is about 1.25 times higher than the NTSC colour carrier. This numer is sufficient enough to create a circuit that generates the right frequency from something that's timed almost like the original Amiga NTSC timing:

PAL colour carrier is 4.43361875MHz. Divide this by 1.25, and you get 3.546895. This is the "new" chipset clock CCK (also known as "colour clock"). Multiply this by 8 and you get the crystal frequency of the PAL model of 28.37516MHz.

Multiply the CCK by two, and you get the CPU frequency of 7.09379MHz - as opposed to the NTSC CPU frequency of 7.15909MHz. This shows that the CPU of the NTSC version is clocked almost 1% faster. Further, the NTSC video system has less video lines, but comparable syncing periods, giving a higher sync time vs. picture time rate, essentially lowering memory performance requirements. This should give another tiny performance boost, because memory is statistically free for more CPU cycles than video cycles (that's in systems without fastmem).

Conclusion:
You will need the right crystal frequency to operate the Amiga on a video monitor, but you will not have to exchange the Agnus chip. Only if you want your system to *cold*start* in your desired mode, changing the Agnus is required.

AmigaManiac's video converter may give you a colour picture on a video monitor even if you have the wrong crystal in the computer. However, his colour clock is NOT in sync with the rest of the chipset. This is bad design practise, as it'll produce constantly moving interference of the colour carrier on the picture. Both the NTSC and PAL video system were designed to get around such interference by syncing the colour carrier with the HSync signal, and the Amiga chipset is making good use of it. I'd suggest to look for an A520 of the right video system, and have the correct crystal frequency in your Amiga - this will give the best possible picture, one that's worthy of an Amiga.

Jens

Hmmm, based on this information Im surprised that my PAL 500 is able to run at 7.15909MHz in NTSC mode despite having a 28.37516MHz clock crystal.



Im running a full ECS Chipset on a German Rev6a Mobo with Chip-Ram Mod (my Rev8a was killed by a leaking battery).