My Bargain priced GX4000 arrived today now to mod it!

[Badstarr]

Hi all,


I just got a GX4000, it's the second one I've owned since my last one never worked properly I'm going to mod this like crazy, so has anyone any suggestions. It will be a week or so before I crack open its case as I'm currently having a hell of a time installing a new exhaust on my car and that has to take priority (25 year old cars love to hang on to their components!  )


My first project with the GX4000 is to convert it into a real CPC, I'm trying to source an old 6128 to donate some parts, but ebay isn't providing the goods right now. I may have to use my old 464 but I wanted to add disk support.


So what do you think? What would be the ultimate GX400/CPC hybrid??

[redbox]

This sounds like a good project and one I'm really interested in.


I got a GX4000 because I wanted the cartridge and it was cheaper than the standalone cartridges on ebay     It's disposable too, so if I wreck it in the process it can always be a 'donor' vehicle to fix a Plus one day!


But as where to start... I have no idea! 

[Bryce]

I'd definitely put a disc controller in it and then add an internal HxC with every game you can think off. A USB/PS/2 keyboard socket, a multi-cartridge system and a MegaFlash might also be worth adding. Another idea might be to make the controllers wireless?

Bryce.

[Badstarr]

Hmmm, wireless controllers! Now there's an idea! Should be something that's fairly easy to do as the communication is one way. I'm definitely going to add a disc controller, that's why I need a donor 6128 to harvest the keyboard and the Disc interface chips. Hopefully then all I will have to do is copy the plus circuit connections etc. HxC would be good too. MegaFlash is a must, are they still available? I would love to have one when I get next month's wages! I have two Cartridges that I will probably never use Burnin Rubber and No Exit so I will convert these to contain a multi cart system. I'm definitely going to make a USB mouse interface as I really want a mouse to use on my CPCs.


Great ideas, keep em coming!

[Badstarr]

Just thought I would ask, does anyone know if the reduced clock speed of the GX4000 is enough to skew disc access timings at all? Or does it not matter?

[TFM]

Just thought I would ask, does anyone know if the reduced clock speed of the GX4000 is enough to skew disc access timings at all? Or does it not matter?

Reduces clock speed? It's as fast as a CPC.

[Badstarr]

I thought the GX4000 was clocked slightly lower than the CPC to improve the picture quality? If I'm wrong then no probs, I was just a bit concerned that the disc drive may not work correctly if the clock speed is different.

[steve]

You might try to connect the GX4000 to the expansion port of the CPC6128 using 512kb of dual port ram that looks like a cartridge to the GX4000 and ram expansion  to the CPC, so it is used as a graphics card and additional sound channels, maybe even 4 joystick ports.

[TFM]

I thought the GX4000 was clocked slightly lower than the CPC to improve the picture quality? If I'm wrong then no probs, I was just a bit concerned that the disc drive may not work correctly if the clock speed is different.

Well, The Cranium took a GX4000 and made a complete 6128 Plus out of it, with the advantage of a SCART port :-)   If you like to do that, you must be able to solder wires at the pins of the ASIC.

[Badstarr]

@ steve That's an interesting idea, it could be something I would consider in the future to see what is possible with that kind of arrangement, but really what I'd like to do is have the GX as a standalone system that has loads of bells and whistles. I like the idea of having an HxC installed as it may be possible to install all in the one unit. Some kind of auto load system on ROM might be quite useful for some games that could be loaded without the need for a keyboard, as long as they are playable without one I suppose.


@ TFM/FS Cool! Do you have any links to The Cranium project?

[redbox]

I like the idea of having an HxC installed as it may be possible to install all in the one unit. Some kind of auto load system on ROM might be quite useful for some games that could be loaded without the need for a keyboard, as long as they are playable without one I suppose.

I think this a good idea and is a realistic goal.  So you'd have


- A stock GX4000
- FDC and HxC installed inside
- DIY Cartridge (hack an old cartridge and add a socket) - put new EPROM with BASIC/AMSDOS and loader system in it
- Possibly a 128kb upgrade?


I could write the cartridge software for this and patching games to work solely with the joypad wouldn't be too difficult.  Result would be the ultimate games machine!


I can't see any room on the GX4000 motherboard for installing a FDC.  Got any idea where it could connect?

[MacDeath]

Why re-invent the 6128PLUS ? 

Possibly a 128kb upgrade?

While at it, directly aim for +512K RAM...

How would you do for the keyboard ?

reduced clock speed of the GX4000

It's not like the GX4000 runs at 2mhz... From what I remember its more like 3,99 instead of 4...


Anyway, you may need a good old CPC6128 to cannibalize bits...

BTW on the same vein (vain ?) does anyone knows if CPC464 or 6128 are suitable to cannibalize in order to add the tape port on the 6128PLUS ?
Also are the RAM chips compatible with PLUS' ?
What about the FDC ?

[Badstarr]

Thanks for the offer Redbox, I may have to take you up on that! I definitely want to add more RAM. There is no existing vacant socket on the GX4000 for the FDC etc but I think I will simply make a card with the components on it and wire them up accordingly, hopefully with some careful thinking this could be installed in the case with a port made to use an external disk drive. I think it should be possible to use a ribbon/ide cable to route an expansion port out the left hand side of the machine sort of in the grove/handle style part of the case. The monitor port could give way to a tape socket. I'm thinking the analogue joy stick port could be replaced with a keyboard/mouse socket so can easily be disconnected when not in use. It may get a little crowded in the GX4000 so I will have to work out what's sensible to have in the case.

[MacDeath]

with this additionnal RAM you may then play the Fabulous and Awesome Rick Dangerous 128PLUS...

There is no existing vacant socket on the GX4000

That's the point : GX4000 PCB has simply no free space to add stuff.
You need to design a proper additionnal PCB and put it "under" the GX motherboard, with quite difficult wirings and so on.

Why under ? because the Cart port is on the up-side...
or a card with a hole so you can put it above instead...

Anyway good luck and please feel obliged to do some tutorials and reports and videos and pictures of the courageous act.

Also beware... some Chips may need to have some space on them so they can cool fairly...

Even a Z80 may overheat... I guess.

[Badstarr]

I don't see it as inventing the 6128 plus really, more like retro fitting the parts Amstrad removed, 6128 plus machines are hard to find these days, I was lucky enough to find my upgraded 464 plus and I would be really annoyed if it got wrecked and I doubt it would be replaceable in a short amount of time. The other thing is that gx4000 machines show up all the time on ebay and they are just crying out to be modded in my opinion. Even if they seem to be selling for high sums of money these days.


There will need to be a lot of careful thought put into circuit arrangements, but years of playing Tetris and living in small rooms should help with this! lol!


Some cooling method may be required as that transistor in the GX does produce a fair bit of heat and adding more stuff will surely only add to this.


I like a challenge! When my new soldering gear arrives and I've fixed my car the work on the GX4000 will begin!


I will definitely document and record the mod as much as I can, I wont be biting holes in the casing this time and having to tidy up afterwards lol! I hope that this project will allow people to get their hands on some CPC Plus goodness without having to use an emulator if they want to reproduce the project, that's assuming its a success.

[redbox]

@MacDeath - I too don't see it as re-inventing a 6128 Plus.  A GX4000 with a FDC/HxC would be a nice gaming platform that I could easily slot under the TV and use to play CPC games whenever I want.

@Badstarr - your project is ambitious, but would be awesome if you could pull it off.  I suggest starting with a DIY cartridge - then, if you have an EPROM programmer, you can play any cartridge game you want and also you can squeeze a fair few traditional CPC games into a 512kb ROM 

[Badstarr]

That's the idea Redbox, I can leave my plus happily where it is and have a machine I can use on a bigger screen rather than moving my CPC from room to room. Obviously I need to get a few parts before any significant work can begin, but first I intend to figure out what components need to be connected to where so I will start mapping all that next week. Can't wait! 

[redbox]

Found this: HOW TO MAKE A REAL PLUS OUT OF A GX-4000

Looks  Cranium did it with a DDI-1.

[Bryce]

The GX4000s base clock is 39.9Mhz (to match the TV frequency more accurately) instead of the 40Mhz in the CPC, this makes it 0.25% slower, but as far as I know it doesn't negatively effect the FDC.

@MacDeath: The RAM ICs in the classic CPC aren't compatible with the plus or the GX4000. What parts do you need to add a tape port to a Plus? The socket and a few wires cost almost nothing and aren't worth destroying a good CPC for!

Getting that much into a GX4000 will be a challenge, but if you plan it well I think it would be possible. And you won't need to worry about cooling for the ICs, they all run well below their threshold and I very much doubt they get hot even after a marathon gaming session.

Bryce.

[Xyphoe]

The GX4000s base clock is 39.9Mhz (to match the TV frequency more accurately) instead of the 40Mhz in the CPC, this makes it 0.25% slower, but as far as I know it doesn't negatively effect the FDC.

Could that be the reason the GX4000 version of Batman The Movie suffers nasty slow down when too many sprites are on screen compared to the 464 original that doesn't?

[Xyphoe]

I'm currently having a hell of a time installing a new exhaust on my car and that has to take priority (25 year old cars love to hang on to their components!  )

Hahaaa! Tell me about, it! Just literally last week I had a hell of a job changing the entire exhaust system on my ALSO 25 year old car! 
What is it you have?

80's cars were the best ... as were the computers .... the music ....

[Badstarr]

Hi Xyphoe! So you are a retro car owner too! Mine is a Nissan Sunny Coupe, one of only 19 of it's type left in the country. I see it as the Amstrad CPC of cars and it's currently consuming a fair bit of my income!


What car do you own?

[Xyphoe]

Hi Xyphoe! So you are a retro car owner too! Mine is a Nissan Sunny Coupe, one of only 19 of it's type left in the country. I see it as the Amstrad CPC of cars and it's currently consuming a fair bit of my income!

What car do you own?

Oooh yes they are quite rare now! I take it that it's a B12 series? I liked the looks of that run the best - had a sexy rear end  lol B13 had the next best looks. I like my Jap cars of the 80's to early 90's - had a Mazda 323F for many many years and loved it to bits (but it also ended up in bits when it went into a crash barrier  )- very nearly got a Mitsubishi Starion or a Nissan ZX300 (wow!) next ... but sorry to disappoint I defected away from Japan to Germany, and now have a (1985) Porsche 944 LUX to tinker around with!

[Bryce]

Oh, I had a Nissan Sunny Coupe back in the 90's (94 to 96 as far as I can remember). It was a really great car, one of my favourites. I sold it eventually when it had way too many Km on the clock and I was spending more time fixing it than driving it. You still see them on the road sometimes here.

Bryce.

[Executioner]

Nissan Sunny Coupe, one of only 19 of it's type left in the country. I see it as the Amstrad CPC of cars....

Everyone's entitled to their own opinion, but, comparing a CPC to a Nissan Sunny is some kind of joke, surely.