Super turbo PCB layout

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By sdsnatcher73

Prophet (3532)

Аватар пользователя sdsnatcher73

13-09-2021, 15:40

[dream]Yeah that is the difficult part… what if instead of a Raspberry Pi it would use Z80 and R800 in FPGA, those implementations are quite mature (well Z80 part). Basically take an OCM but only use CPU and S1990 stuff… [/dream]

But R800 for most purposes is not needed, a fast Z80 for use in Nextor should be enough. Software switchable speed could be great for e.g. SofaRun (so Games that need to can run on low speed).

By lintweaker

Champion (437)

Аватар пользователя lintweaker

14-09-2021, 07:47

sdsnatcher73 wrote:

[dream]Yeah that is the difficult part… what if instead of a Raspberry Pi it would use Z80 and R800 in FPGA, those implementations are quite mature (well Z80 part). Basically take an OCM but only use CPU and S1990 stuff… [/dream]

But R800 for most purposes is not needed, a fast Z80 for use in Nextor should be enough. Software switchable speed could be great for e.g. SofaRun (so Games that need to can run on low speed).

I have such -half finished- project. Z80 (T80 based) in FPGA to substitute a real Z80. Must finish that someday...first finish playing with a Z380 to seen how that fares...

By SkalTura

Champion (360)

Аватар пользователя SkalTura

14-09-2021, 11:57

If you need help designing a PCB for it, you know where to find me... ;-)

By rigues

Supporter (5)

Аватар пользователя rigues

13-01-2022, 00:52

Hey @SkalTura, I finally got around to trying to build the PCB, but have a few questions regarding component values. Can you help me?

1) Is C5 330pf ceramic?
2) Is C6 (near the crystals) a 10uF electrolytic?
3) What are the values for C7, C8 and C9? I'm guessing C8 is the one near U2, correct? Silk is sometimes a little hard to read.

As for installation, is it a "drop-in" replacement for the Z80? Or do I have to run wires somewhere else on the board?

Thanks for the design!

By SkalTura

Champion (360)

Аватар пользователя SkalTura

25-01-2022, 15:02

@rigues: All capacitors (and resistors) are SMD 0805, except for C6.
C6 is 10uF/16v Tantalum or Aluminum Electrolytic (but a small radial would also fit).
C7, C8, C9 are 100nF (decouple capacitors for the logic IC's).

Note: I only designed the PCB for this project, I have no information about how to use/install it in your MSX...

By jltursan

Prophet (2619)

Аватар пользователя jltursan

25-01-2022, 16:27

IIRC it was Gregory who mounted the PCB, it shared some pics but sadly no one of the assembled board and the flying wires. Anyway, he said that only needed to wire the diodes. Probably the original circuit document could be more clear about this subject...

By msxmakers

Champion (473)

Аватар пользователя msxmakers

12-07-2022, 15:53

Dear partners.
Nobody finished this build?
I do. Just so everyone knows, I think we should say something here for any new builders. Things I understood correctly I hope, if something is wrong please say so.
First, I think you always have to disconnect the VDP clock, pin 8, from the main board.
Second, depending on your MSX model I think it is not always good to connect the R8 resistor to the clock pin of the z80, depending on the MSX model that clock may come buffered from the vdp and the most correct thing would be to connect the new clock there (on the motherboard, pin 8 of the vdp). Perhaps this is the reason for the existence of R8.
Third, the clock generated by the VDP must be redirected to connect it to the sound circuit (PSG) and to the composite video output (as long as it is an NTSC system) otherwise the composite video will not work and the sound will work defectively.
Fourth, it appears that the z80's footprint is QFP44 with the pins clipped. Therefore, you have to cut each pin and then solder the chip.
Fifth, this design didn't make it easy to add a switch or led connection, it would be nice if kicad's design was completely shared or at least someone made the led and diode holes bigger.
Thanks to anyone for any answer you can give me. Despite some hiccups, I have it working on my Omega MSX2+.
I congratulate everyone for the work, the circuit designers, the pcb designer and everyone here for a brilliant collective work.
Greetings.

By msxmakers

Champion (473)

Аватар пользователя msxmakers

12-07-2022, 16:16

I copy here a couple of images.
Here's how the z80 QFP44 looks trimmed and soldered.

Here's how I modified R8 & the clock output to be connected to the motherboard.

Here's a view for the QFP44 chip with some pin cutted.

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