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Author Topic: Like a Z180, but much better ... the Z280 (Read 1046 times)

Online elmer

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Like a Z180, but much better ... the Z280
« on: 2021.January.19. 23:00:44 »
I can see that there are a number of threads where people have talked about putting a Z180 into an Enterprise ... but how about the Z180's bigger and better (but less successful) cousin from 1987, the Z280?

It runs on 5V, it has a Z80-compatible bus mode, and it offers internal clock-doubling!  :shock:

I didn't think that there would be any of the chips still available, but apparently there are still a *few* for sale.

Online gflorez

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Re: Like a Z180, but much better ... the Z280
« Reply #1 on: 2021.January.19. 23:53:22 »
I like that game...

Online elmer

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Re: Like a Z180, but much better ... the Z280
« Reply #2 on: 2021.January.20. 00:04:42 »
It runs on 5V, it has a Z80-compatible bus mode, and it offers internal clock-doubling!  :shock:

Oh dear, no it doesn't! :oops:

Wikipedia is wrong and it offers clock-division instead, so the CPU clock can be 1,2, or 4x the bus clock, but you've still got to give the CPU a higher clock speed.

That presumably means that it would need a board with its own clock, and then either feed that clock into the Enterprise motherboard, or directly tap the Enterprise's own 8MHz or 12MHz clock signal.

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Re: Like a Z180, but much better ... the Z280
« Reply #3 on: 2021.January.20. 00:22:15 »
Have you read this thread about overclocking the EP?

Thanks to this tutorial from Zozo there are a lot of EPs running up to 10Mhz flawlessly.

I have successfully modified three machines.

Online elmer

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Re: Like a Z180, but much better ... the Z280
« Reply #4 on: 2021.January.20. 22:12:01 »
Have you read this thread about overclocking the EP?

Thanks!

I read it again, and if I am understanding it, any replacement CPU *MUST* use the clock from the Nick chip, or accesses to video memory will break.

It seems as though Zozo and you other hardware-experts have already tested and figured out how to overclock Dave with a 20MHz (or 16MHz) crystal, and so use a 10MHz (or 8MHz) CPU.

From my POV, I think that I prefer the idea of running the computer at 8MHz rather than 10MHz, because then all of Dave's audio register values just need to be doubled in order to get the correct frequencies for any game sound.

Somehow it also just seems like a more reasonable speed for CPUs in the late 1980s, when the Z280 came out.

From my personal curiosity, I wonder what an Enterprise-sequel could have looked like back in 1987-1989.

As soon as you get much further than those years, it was becoming clear that the IBM PC and its clones were going to take over the entire home-computer market. :ds_icon_frown:
« Last Edit: 2021.January.20. 22:26:21 by elmer »

Online gflorez

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Re: Like a Z180, but much better ... the Z280
« Reply #5 on: 2021.January.21. 00:18:21 »
Ok... I am an expert on nothing... only an enthusiast apprentice that repeats like a parrot what Zozo, Istvan, LGB, Geco and a long list of other geniuses say here, on recent times including you.

I have managed to modify three computers, and this means exactly that. The research of the information that has lead to the knowledge is the work of Zozo, but not only from him, because overclocking on the EP has some tradition on Hungary, with even commercial products, or at least is what I have understood, when Zozo mentions one type of clock switch better than the one he uses.  

Also is truth that the EP was projected with a 6Mhz Z80 clock in mind, some proofs can be seen on its code, ask Bruce about it.

And now that you mention the Enterprise sequel.... it was already projected, effectively with a 6Mhz clock as standard. It had shape and was real, now we know. You can see it on Werner's thread.
« Last Edit: 2021.January.21. 00:24:48 by gflorez »

Offline geco

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Re: Like a Z180, but much better ... the Z280
« Reply #6 on: 2021.January.21. 08:50:17 »
Unfortunately Enterprise 911 was not a real sequel, they just inserted a 6MHz z80 CPU, additional RAM, if i remember well it had 320KB, and a 3,5' floppy was built in.

From my POV, I think that I prefer the idea of running the computer at 8MHz rather than 10MHz, because then all of Dave's audio register values just need to be doubled in order to get the correct frequencies for any game sound.
If we check overclocking from Dave's perspective then the best is 6MHz, because by setting bit1 of 0bfh port Dave behaviour will be the same like on a 4MHz machine, but anyway i think 6MHz should be the base of Enterprise instead of 4MHz, and 8MHz is a good choice.
The best thing in Zozo's turbo realisation, that you can switch between the CPU speeds on the fly, and you can turn back to 4MHz when you want.

Offline Zozosoft

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Re: Like a Z180, but much better ... the Z280
« Reply #7 on: 2021.January.21. 10:23:06 »
Z180 main advantage, it is still in production (like the normal Z80), easy to get it. Previously I never see any available Z280! (And at this case, the price: 8.99$ + 44.06$ shipping to Hungary, +27% VAT -> 67.37$ total price)

I currently don't know, but how about internal I/O registers? There are also problem with Z180, but least can relocated (EXOS 2.4 move these to 40-7Fh, for avoid collosion with EXDOS card).

The whole Z180 idea come from a interview with a Vilmos Kopácsy (director of Hungarian Enterprise representation company), he told "there is a new Enterprise with a Hitachi Super Z80"...
Now we know from Werner Lindner (technical director of the German Enterprise Computers GmbH), this is totaly fake, just talked about some ideas, when drinking beers with Mr. Kopácsy at Munich.

But when I started to put Z180 to Enterprise don't know the words about the new model are fake... :roll:

Offline BruceTanner

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Re: Like a Z180, but much better ... the Z280
« Reply #8 on: 2021.January.21. 12:11:58 »
But when I started to put Z180 to Enterprise don't know the words about the new model are fake... :roll:
But if you had not done it you would have missed all that fun soldering wires :twisted: :lol:

Offline Zozosoft

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Re: Like a Z180, but much better ... the Z280
« Reply #9 on: 2021.January.21. 13:04:40 »
But if you had not done it you would have missed all that fun soldering wires :twisted: :lol:
:lol:
If someone hasn't seen it yet:
26183-0
26185-1
« Last Edit: 2021.January.21. 15:02:58 by szipucsu »

Offline geco

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Re: Like a Z180, but much better ... the Z280
« Reply #10 on: 2021.January.21. 15:45:43 »
:lol:
If someone hasn't seen it yet:
I did not see, looks like a nightmare :ds_icon_cheesygrin:

Congrat for the soldering without any problem ;)

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Re: Like a Z180, but much better ... the Z280
« Reply #11 on: 2021.January.21. 16:46:38 »
Zozo! You wrote on the other thread how you test what happens when NICK gets a fixed clock. Because you think the NICK chip can't withstand higher clock signals and therefore can't go above 12 MHz. Did something happen to that? Sorry for the wrong English, I will also describe it in Hungarian ... :-)

Zozo! Te írtad a másik szálon, hogy teszteled mi történik, ha a NICK fix órajelet kap, merthogy szerinted a NICK chip nem bírja a magasabb órajeleket és emiatt nem lehet 12 MHz fölé menni. Ezzel történt valami?

Online elmer

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Re: Like a Z180, but much better ... the Z280
« Reply #12 on: 2021.January.21. 17:55:17 »
And now that you mention the Enterprise sequel.... it was already projected, effectively with a 6Mhz clock as standard. It had shape and was real, now we know. You can see it on Werner's thread.

Yes, I have read that thread, and I would have loved to have one of those machines! :)

I would like to create something similar to that today, with SD card instead of the floppy ... but now that I know that I have the bad Nick chip in my Egyptian EP64, I have to wait until I can find an affordable Enterprise (or just motherboard) that has a good Nick chip on it. :(


Unfortunately Enterprise 911 was not a real sequel, they just inserted a 6MHz z80 CPU, additional RAM, if i remember well it had 320KB, and a 3,5' floppy was built in.

Back in the 1980's, I would have happily seen that as a worthy sequel to the EP128! ;-)

As I work with the IS-DOS source code, I have finally remembered that I took a similar path from the old-and-slow M80/L80 to the fast Z80ASM back in 1986.

I have also remembered that I abandoned using the EP128 as my primary development machine sometime back then, precisely because it didn't have enough memory to run a useful sized RAMdisk.

IIRC Gryzor (and maybe Renegade) was actually written on an Amstrad 6128 with both the DK'Tronics 256KB RAM and 256KB Silicon Disc expansion boards.  There is an old magazine interview from the time that mentions me using that as my Gryzor development system.


If we check overclocking from Dave's perspective then the best is 6MHz, because by setting bit1 of 0bfh port Dave behaviour will be the same like on a 4MHz machine, but anyway i think 6MHz should be the base of Enterprise instead of 4MHz, and 8MHz is a good choice.

Yes, 6MHz is the obvious choice for an upgrade, precisely for that reason, and it would have been a good Z80 upgrade speed back in the 1980s.

But when thinking of a Z280, which probably wouldn't even have been affordable to put into a home computer at the time, 6MHz seems just a little to slow! :mrgreen:


The best thing in Zozo's turbo realisation, that you can switch between the CPU speeds on the fly, and you can turn back to 4MHz when you want.

That is perfect for a Z80 upgrade, but it really wouldn't work out quite as well for a Z180 or Z280 upgrade, because they will run faster than a Z80 at the same clock speed because of the CPU pipelining.


Z180 main advantage, it is still in production (like the normal Z80), easy to get it. Previously I never see any available Z280! (And at this case, the price: 8.99$ + 44.06$ shipping to Hungary, +27% VAT -> 67.37$ total price)

If you want me to get you one or more of those chips, it seems like a small (<0.22KG) package costs me $15.25 to send to Hungary, and tax is 7% here.  I don't know if they would charge you VAT at the receiving end if the package is marked as a "gift".

Errrm ... I also still have 2 512KB memory expansion boards left for sale! :lol:


I currently don't know, but how about internal I/O registers? There are also problem with Z180, but least can relocated (EXOS 2.4 move these to 40-7Fh, for avoid collosion with EXDOS card).

Yes, I've heard that the internal I/O locations on the Z180 can cause problems.

There is also the unfixable problem that it doesn't (AFAIK) work with the undocumented IXH/IXL/IYH/IYL opcodes that were widely used by Z80 programmers in the 1980s.

The Z280 puts it internal I/O registers into a different 64KB I/O region (I/O addresses are 24-bit), and it does officially support those previously-undocumented IXH/IXL/IYH/IYL instructions.

OTOH, it would need a small PCB designed for it, both because it is a PLCC chip, and also because it needs a TTL 8-bit latch added for the low 8-bits of the address bus. But IMHO that also gives you a good location to add the 20MHz, 16MHz, or 12MHz TTL oscillator that you need to use!
« Last Edit: 2021.January.21. 18:06:13 by elmer »

Online gflorez

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Re: Like a Z180, but much better ... the Z280
« Reply #13 on: 2021.January.21. 20:24:26 »
I would like to create something similar to that today, with SD card instead of the floppy ...

The software of the SD cartridge is so well written(by Zozo, of course) that it doesn't need to be on the cartridge address range, 03-07, an external cartridge bay can be connected on the expansion connector on other selectable range.

Then, you can have the SD cartridge as if it were the EXDOS interface, at the right side, leaving the cartridge bay for other tasks.

This external cartridge bay was planned by Zozo when we found that the MIDI interface Rom only was able to work on the 07 segment. Since then Geco has fixed the Rom in several ways.

Online elmer

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Re: Like a Z180, but much better ... the Z280
« Reply #14 on: 2021.January.21. 21:16:36 »
OTOH, it would need a small PCB designed for it, both because it is a PLCC chip, and also because it needs a TTL 8-bit latch added for the low 8-bits of the address bus. But IMHO that also gives you a good location to add the 20MHz, 16MHz, or 12MHz TTL oscillator that you need to use!

Damn! It looks like the Z280 is probably not going to be a good match for the Enterprise ... the CPU itself runs at half the speed of the external clock. :cry: