GX4000 becomes a 6128 Plus!

[Badstarr]

21 years ago today i recieved an Amstrad CPC 6128 for my birthday, 21 years later I have (sort of) built my own, well there is a bit more to do to complete it.


I built a PCB to add the disk drive interface to the GX4000 main board but after checking it I found a problem so I went back to basics and built a point to point version, that too had a problem and after testing all the connections I couldn't find a problem, then completely by chance I lifted the board and in doing so applied a little pressure to the SED data separator and the read fail messages stopped momentarily! So I pushed the IC into the socket a little harder and it worked! And some say brute force doesn't fix anything!


So here it is, in this hastily thrown together video, a GX4000 loading from disc! I'm enjoying the exquisite weirdness of watching not only a GX4000 load from disk but also the fact that something I built of this complexity actually working!



GX4000 becomes 6128 Plus - YouTube


Next up, I have to put all the pieces into the 464 case properly and then start my 512k RAM expansion...

[redbox]

That is so cool it hurts 

Congratulations!

[Badstarr]

Thanks redbox!  I'm over the moon that its working now!

[TFM]

Just saw the video! Great work!

[Badstarr]

Thanks TFM/FS! :-D I think soon we should work out a way of benchmarking the machine so we can get some idea of the difference, if any that the slightly lower clock speed makes in comparison to a standard CPC I can detect some minor differences when watching the BMF demo eg. Sounds happen slightly later than on my other machines but then again it may just be my brain playing tricks!

[00WReX]

Very nice work...so lucky you found that bad connection or this may have been relegated to the cupboard for another 10 years 
Thanks for sharing the video...always good to see photo's & video's 

Cheers,
Shane

[Kris]

Amazing work ! Congratulations

[Gryzor]

A freak of nature! Cool!

[Badstarr]

Thanks everyone for the positive comments! And the 'likes' :-D it all helps keep the motivation going! When I tell most of my mates about this project they tend to look at the ground and mutter something about leaving the gas on before running away so its nice to know there's people out there who share my enthusiasm for the good old CPC!

As for my progress with this machine, I'm having to redesign the layout of the FDD hardware as its just way too big to fit into the case without wedging it in in a way that will risk fatiguing the solder joints which wouldn't be good for long term reliability. Should have maybe given this a little more thought before hand but we live and learn.

I have some ideas for the 512k RAM expansion, I'm either going to reuse some DRAM ICs from an old Amiga 500 upgrade card that has a rather badly corroded battery, along with a custom made PAL assuming my programmer is capable of programming it. If the RAM is no good I have 20 KM41464AP12 ICs on order so I could easily build one from those, but this option would take up quite a bit of space  so its fingers crossed for the first option.:-)

[Badstarr]

Quick update! Been mega busy so haven't had a lot of time to make much more progress but I did find time to finish the FDD hardware re-jig and the final board is much smaller and has its logic ICs the right way up lol! It's working great and is now test fitted inside the 464 case along with the (made by Bryce) MegaFlash! The FDD controller piggy backs onto the MegaFlash data bus as this was the most efficient way to utilise the space. There was no way to fit my DIY version inside the machine so this one will be used externally now.

I now need to figure out how I'm to route the external expansion bus, its a real rats nest inside the case so optimising the wiring will be my next main concern but it all fits in there and everything seems to be playing nice! There should be plenty of room for the HxC just need to give some thought to where I can put the screen.

The only slight issue I've noticed is that I'm occassionally getting some audio glitches but I'm going to post a new topic to discuss this with anyone that might have some ideas.

Anyway here is a quick snap of the new FDD board with the old one for comparison...

[Bryce]

Looks much neater.

Oooo, "dead insect" logic on the old board

Bryce.

[Badstarr]

Lol! The fact that I managed to solder all the logic the wrong way round is quite amazing really thank god for deadbugging!