Super turbo PCB layout

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By SkalTura

Champion (315)

SkalTura's picture

29-04-2021, 07:03

sdsnatcher73 wrote:

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).

The eZ80 had 100 pins, the "normal" Z80 QFP has 44 pins. So that will only increase the size of the PCB, and I think that is what we are all trying to prevent here...

By SkalTura

Champion (315)

SkalTura's picture

29-04-2021, 07:11

In the 74HC schematic, 2 crystals are drawn, and I guess I can eliminate the "low speed" crystal, right...?
That would also reduce the number of components and PCB traces a bit, and maybe then I can also make this version work.
Saved people from having to buy a programmer for the GAL.
Or do you all want the GAL version...?

By lintweaker

Champion (395)

lintweaker's picture

29-04-2021, 07:39

Yes, it is possible to use just one crystal to get both needed frequencies. The CIEL turbo is an example.
Using programmable logic can keep the BOM cost/count down. Only downside is the need to program the device. Not everybody has a programmer lying around. Programming a SMD (e.g. TSOP/SOIC) version could be even more challenging (most programmers come with a set of TSOP/SOIC adapters).

A modern, readily available PAL replacement could be ATF20V8 or ATF22V10. So far I've only used DIP versions of these.

By sdsnatcher73

Paragon (1740)

sdsnatcher73's picture

29-04-2021, 08:53

SkalTura wrote:
sdsnatcher73 wrote:

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).

The eZ80 had 100 pins, the "normal" Z80 QFP has 44 pins. So that will only increase the size of the PCB, and I think that is what we are all trying to prevent here...

Yeah I agree, this was just in response to the 21MHz version that was mentioned, if pure speed is what you want. It would require much more investigation to see if it is usable in existing MSX’s or even newly designed ones.

By sdsnatcher73

Paragon (1740)

sdsnatcher73's picture

29-04-2021, 09:06

lintweaker wrote:

Yes, it is possible to use just one crystal to get both needed frequencies. The CIEL turbo is an example.
Using programmable logic can keep the BOM cost/count down. Only downside is the need to program the device. Not everybody has a programmer lying around. Programming a SMD (e.g. TSOP/SOIC) version could be even more challenging (most programmers come with a set of TSOP/SOIC adapters).

A modern, readily available PAL replacement could be ATF20V8 or ATF22V10. So far I've only used DIP versions of these.

The question is of course, do we expect people to build these themselves or will someone start creating batches of these. I would hope for the latter. Making larger batches would reduce component cost. IMHO someone making quality upgrade kits we would want the version with GAL or equivalent. That person (or persons) making some money out of it is no problem. I think €30 for a preassembled board is a reasonable sales price. I reckon that would cover BOM and some time for building them. Of course nobody is in it to get rich here, that is impossible. But getting something back for the time you put into it is very reasonable.

By SkalTura

Champion (315)

SkalTura's picture

29-04-2021, 12:11

sdsnatcher73 wrote:

The question is of course, do we expect people to build these themselves or will someone start creating batches of these. I would hope for the latter. Making larger batches would reduce component cost. IMHO someone making quality upgrade kits we would want the version with GAL or equivalent. That person (or persons) making some money out of it is no problem. I think €30 for a preassembled board is a reasonable sales price. I reckon that would cover BOM and some time for building them. Of course nobody is in it to get rich here, that is impossible. But getting something back for the time you put into it is very reasonable.

But, Is there a need for this ?
Because this topic seems to escalate from a simple question about a missing PCB file, into a complete off-the-shelve product?

I mean, I'm happy to design the PCB file for this (and maybe get a small percentage for the time and effort), but I'm not going to do all the logistics in producing and selling compete assembled boards...

And I'm still confused about the pin3 on the GAL version...
If this is for software switching, were does it need to go on the PCB/Z80, or is this going to be a wire to some other components in the MSX ?
Can't design a PCB if I don't know what is needed or where all the pins go to...

By lintweaker

Champion (395)

lintweaker's picture

29-04-2021, 12:44

SkalTura wrote:

And I'm still confused about the pin3 on the GAL version...
If this is for software switching, were does it need to go on the PCB/Z80, or is this going to be a wire to some other components in the MSX ?

Pin 3 goes to IO address decoder logic (74LS138) to make it react to IO port 0b6h.

By SkalTura

Champion (315)

SkalTura's picture

29-04-2021, 13:24

lintweakerPin 3 goes to IO address decoder logic (74LS138) to make it react to IO port 0b6h.[/quote wrote:

So that will need to be a wire then...?

By lintweaker

Champion (395)

lintweaker's picture

29-04-2021, 13:42

SkalTura wrote:

[quote=lintweakerPin 3 goes to IO address decoder logic (74LS138) to make it react to IO port 0b6h.

So that will need to be a wire then...?

Yes, but we cannot just replicate it. IO port 0b6h was specifically there in the CIEL design. If want the 7MHz / turbo to be switchable via IO port we need to add our own IO decoder. This requires a lot of additional inputs on the GAL which are not there so another or bigger GAL/CPLD would need to be added.

By SkalTura

Champion (315)

SkalTura's picture

29-04-2021, 13:52

Eeeuhhh...... So the GAL version cannot be used then.
Or someone needs to make a new version of the design and software.

Okay, I will pause the GAL version PCB for now and focus on the 74HC version instead...

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