Resetting the Region of a CPC..?

[Charlie...]

Hello,
Lurking about here has brought back happy memories of past CPC ownership...
...time to go get one again and do some hacking - I'm not very good @ leaving retro systems standard. The dining room table is usually covered in the guts of something or other while undergoing whatever evil plan I have in mind.


This brings up a question or two:
I'm after a 1/2 decent 6128, I don't necessarily want a monitor. Examples seem to come up much more often (and cheaply) on German/French fleaBay than the UK. That possibly means a Schneider as I'm not used to the AZERTY keyboard found on French versions. The 'proper' ports on the German version may actually be quite nice to have.

I vaguely remember (nil found on a quick google) that all 'Amstrads' are the same. The region (language too?) is set by a solder pad on the motherboard. Am I correct?
If so is it feasible to buy a Schneider 6128, change the region setting to UK and have it run as an English Language machine? No need to change the ROM..?

Thank you!

[Devilmarkus]

Only the brand names are changeable via soldered bridges.
The keyboard layout depends on the different ROMs itself.
(Means: An UK rom always has QWERTY keyboard but the name is changeable)
BTW.: [ size] is not supported as you use here Use the functions from the Editor above please.

[MacDeath]

Hi Charlie.

Perhaps you should register to be more than a guest...



Yes it depend of the ROM your CPC has.
This mean unsolder the ROMs and perhaps getting a socket on the motherboard, then off course getting proper EEPROM or ROMs...
perhaps an external ROMbox may work too.


That's the main advantage to have a 6128PLUS : the ROM is on a cartridge : easier to Hack or change...

[Gryzor]

The CPC is region-free. It will play games from all regions

[MacDeath]

Yeah the Amstrad CPC is region free...

But what about the Schneider CPC ?
Those German love to be exclusive...

[Bryce]

I still haven't found the slot to insert the DVD, so I can't confirm whether my Schneider is region-free.

Bryce.

[Charlie]

Thanks for the replies chaps. My activation just came through so I can be myself.
So...
An 'Amstrad' is an Amstrad no matter what region it's from. But the jumpers I remember only change the  line @ the top of the screen - If I want an English language ROM I either get a UK computer or burn my own ROM. (or get a +)
Right, it all depends on how impatient / cheap I'm feeling...
There seem to be a lot of fun projects to build round here, must get my hands on one soon.


Somewhat OT:
I see from the Wiki the Amstrad can stand a 24Mhz crystal, but not 'on the fly' changes...
I wonder:
-32Mhz..?
-Really no on the fly changes..?
-Maybe septate crystals for different sub-systems..?
Sounds like a project to me...

[Bryce]

There are several ways to change the CPC frequency on the fly and upping the frequency above 24Mhz.

If you want to go above 24Mhz you would have to poll the IORQ signal on the Z80, then switch to the higher frequency (whatever the CPU can take) when this signal is 1 and back to the lower frequency when the signal is zero. This way, the CPU will rise to the higher frequency when it's not talking with external components and all other parts stay at the same lower frequency. This has to be sequenced correctly (using a single clock with a clock divider for the lower frequency) because the CPU will run at a different frequency as the other components. Doing such overclocks can mess up lots of things, such as the sound and   graphics because the CPC starts sending new data before the last data   has been fully processed.


Manually switching on the fly would also require some circuitry to switch at exactly the correct time, a simple switch would cause too much bounce and the CPU would crash.

I made a very similar circuit for an Atari 800XL a looong time ago, but I've no idea what I did with it or the schematics, will have to go looking.


Bryce.

[arnoldemu]

Thanks for the replies chaps. My activation just came through so I can be myself.
So...
An 'Amstrad' is an Amstrad no matter what region it's from. But the jumpers I remember only change the  line @ the top of the screen - If I want an English language ROM I either get a UK computer or burn my own ROM. (or get a +)
Right, it all depends on how impatient / cheap I'm feeling...
There seem to be a lot of fun projects to build round here, must get my hands on one soon.


Somewhat OT:
I see from the Wiki the Amstrad can stand a 24Mhz crystal, but not 'on the fly' changes...
I wonder:
-32Mhz..?
-Really no on the fly changes..?
-Maybe septate crystals for different sub-systems..?
Sounds like a project to me...

The memory refresh is done when the gate-array reads the ram when it draws the screen. the crtc provides the address.
This refresh is done for both 1st 64k and 2nd 64k. So you would need to provide your own refresh logic.

The gate-array will stall the cpu for each memory access via a halt, so you would need to monitor the I/O operations to determine if you are accessing rom/ram, and then if the ram is being used by the video system.

Decoupling the rom and extra ram from the wait states would be great, meaning that code could run faster from rom or extra ram.
Also if possible determining the ram for screen and running that at slow mode would also be good.
So in effect, something like the Spectrum where the cpu is slowed only when it performs a read/write of the ram the video system is accessing.

I think clocking the z80 higher is more possible provided you clock it seperately (but perhaps in sync) with the rest of the system.
You could also clock the 8255, ay and fdc at a different rate too. I think the gate-array and crtc need to have the same clocks in order for the video to be stable.
But it would be interesting in what you could do.

[Charlie]

Thanks again...
I'm more familliar with ARM / 68K / 6502 based systems than Z80 ones. Having said that it sounds like elements of this won't be too hard, especialy if I stick with 'just' the CPU and recycle a previous project for the job.