Super turbo PCB layout

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By SkalTura

Champion (346)

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28-04-2021, 07:57

Pentarou wrote:

Finally IMHO, I think people who are looking to have this board manufactured would prefer the Eagle/KiCad files instead of the printouts.

Most PCB manufacturers I know prefer Gerber files, because they won't need to convert them and can be used directly.
And that is what I will be making too.
The printout's were just to show what the PCB will look like...

By sdsnatcher73

Prophet (2340)

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28-04-2021, 13:38

The advantage of this solution over a PCB on top of a DIP Z80, beside being neater, is height of the final solution. This will fit in many more (if not all) MSX machines with space restrictions.

By jltursan

Prophet (2561)

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28-04-2021, 14:38

What's the maximum clock you can feed to the Z80?, is it limited by the MSX or just by the Z80 used?

By sdsnatcher73

Prophet (2340)

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28-04-2021, 14:49

From what I understand it is mostly limited by the VDP in the MSX.

By usuario_msx2

Paladin (755)

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28-04-2021, 16:43

Maximum clok speed with my msx:

Panasonic wx: 10.7mhz mod design by K.Tsujikawa
Philips vg8235: 9mhz (zilog clock generator mod)

Sony hb501f: 9 MHz (zilog clock generator mod)
https://www.flickr.com/photos/44218601@N06/albums/7215767706...

Sony hb f1bxdj
Zilog clock generador mod
https://www.flickr.com/photos/44218601@N06/albums/7215771738...

Dynadata dpc200 7.1 mhz
Philips vg8020 7.1 mhz

No super turbo mod usted with this computers
https://www.flickr.com/photos/44218601@N06/albums/with/72157...

By usuario_msx2

Paladin (755)

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28-04-2021, 16:48

@sdsnatcher
I'm not sure about It....

By Pentarou

Champion (400)

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28-04-2021, 18:00

In theory one could reach the maximum Z80 speed, however the rest of the system was built to run at 3.58MHz, so the real stable speed it's a compromise between RAM/ROM type/speed, PCB quality, which other parts are on the bus, if the Z80 has buffers etc.
I did a few experiments on a 8235 and I could get 12MHz stable enough, however I choose do decrease it a bit to ~10MHz to allow a bit more leeway.
For those interested there's a very interesting article from Eugeny Brychkov here.

SkalTura wrote:

By the way, the adapter PCB on that page has the Z80 pins for mounting only on the bottom, not though-hole. You can see that the QFP pins will otherwise short circuit with them. Using only pins on the bottom and not trough-hole could tare off one of the pins when you try to remove the PCB from the Z80 socket. Not a good way of designing a PCB...

I don't understand what you are referring to, are you talking about the pins that should be used for the 40Dip?
And that PCB is neither my work, neither I was suggesting to use it as-is.

Pin 3 of the GAL is a decoded I/O port address signal, it's for software switching the circuit.
D6 I don't know why it's used.

@usuario_msx2 do you use 9958 with /VDP_WAIT in all those machines?

By Gregory

Master (178)

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28-04-2021, 18:35

sdsnatcher73 wrote:

The advantage of this solution over a PCB on top of a DIP Z80, beside being neater, is height of the final solution. This will fit in many more (if not all) MSX machines with space restrictions.

The 7Mhz upgrade has worked for the past 20+ years, why should it pose a problem now?

By sdsnatcher73

Prophet (2340)

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28-04-2021, 19:35

Gregory wrote:
sdsnatcher73 wrote:

The advantage of this solution over a PCB on top of a DIP Z80, beside being neater, is height of the final solution. This will fit in many more (if not all) MSX machines with space restrictions.

The 7Mhz upgrade has worked for the past 20+ years, why should it pose a problem now?

It has never fitted (physically) in all MSX computers, AFAIK. Of course it fits in NMS8250 and HB-F700P but what about NMS8220? And many new MSX users who are getting multi-purpose carts and use them on MSX1 systems may really enjoy a speed gain in Nextor. And if SofaRun could use the I/O port to switch back to 3.58MHz for gameplay, how cool would that be.

By sdsnatcher73

Prophet (2340)

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28-04-2021, 20:49

If it is highest execution speed one is after, using an eZ80 might be the best to look at. It is fully Z80 binary compatible (but I don’t know if it is pin, I/O and even 5V/TTL compatible). It has some features (like 24bit addressing mode) but we could not use these easily and it would not be necessary. The eZ80, like the R800 uses fewer clocks per instruction, so running one on 7.16 MHz would be equivalent to a Z80 at 21.48MHz. This will surely give problems with games that are not turbo aware.

For MSX-C this may be a nice processor…

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