Is the NEXT an emulator?

[Pegaz]

Thanks @Pegaz,

So there are there particular games that cause issues?

From the top of my head, I will mention what I mostly use as a benchmark, for comparison to the real hardware.
Games: Aquaplane, Vectron, Robocop 3, TV Game, various games with multicolor effects like Uridium, Black Lamp or with Nirvana, Bifrost and similar engine like Old Tower etc.
Demos: Shock Megademo, MDA Demo, MQM5, Paralactica, Tiratok, Mescaline, Rage...
Test programs: ULA48/128, snow, FPGA48all, IR_Contention, Timing Tests 48k, BorderTrix, Scroll17, z80full, z80speed...

There are certainly more relevant examples, but I remember these at the moment...

[+3code]

Reading this thread I feel as in the "Groundhog Day" film.

[Sparky]

[PeterJ]

Games: Aquaplane, Vectron, Robocop 3, TV Game, various games with multicolor effects like Uridium, Black Lamp or with Nirvana, Bifrost and similar engine like Old Tower etc.

Thank you. That list of games is useful. If you find any more please post them. I was aware that Aquaplane had some border effects.

[clebin]

It costs well over ₤300, shouldn't it be full hardware?

Injection moulded custom cases and keyboards are expensive. FPGAs are also expensive. A custom ASIC is a lot cheaper per unit, but you need a massive investment up front to produce one - way beyond any hobby project like this. Who else didn't have the money to produce a custom ASIC? Sinclair, that's who.

This is why the Spectrum is based on a ULA - an Uncommitted Logic Array, also known as a "Gate Array". An FPGA, of course, is simply a "Field-Programmable Gate Array".

Ok, so a ULA is a write-once affair while an FPGA can be written to many times and without specialist hardware. But they're both off-the-shelf blank-slate chips that get populated with a bunch of gates to perform a function. They're both cheap compromises over a custom ASIC. The ULA is just a forerunner of an FPGA. And it's right at the heart of a "real" ZX Spectrum. Hence...

It's a glorified emulator as far as I can tell.

I find it pretty ironic that any Speccy owner would be condescending towards the use of an FPGA!

[Sparky]

FPGAs are the future. It's hard to argue with that, but over 300 Quid for a FPGA that is utilizing emulators more than necessary... It just doesn't sit well with me.
But hey, that's just an opinion, don't take it for more than it is.

[clebin]

FPGAs are the future. It's hard to argue with that, but over 300 Quid for a FPGA that is utilizing emulators more than necessary... It just doesn't sit well with me.

What emulators is it utilising beyond the FPGA? It uses an optional Pi to “play” TZX files but that’s taking the place of the cassette recorder rather than the Spectrum itself.

And if is the FPGA, what do you say to my point about an FPGA being quite strikingly the same in concept as the original Spectrum’s ULA? That argument wouldn’t apply in the Amiga world as it has custom chips, but it seems impossible to ignore for a Spectrum fan.

And I can only repeat the same thing about costs. FPGAs are expensive, custom cases are expensive. That’s where the costs are. No-one’s getting rich, no-one has to buy it, and the project is open-source.

But hey, that's just an opinion, don't take it for more than it is.

Which is fine, but at the beginning of the thread you seemed to suggest that your mind was open and you just wanted info. Now you have these strong opinions about glorified emulation. Have you reached those conclusions during the course of the thread, or were you not being entirely honest at the beginning? It’s just I’ve seen that bait-and-switch happen a little too often over the years.

[Sparky]

I have made my opinion clear. I'm in no mood to argue over such a trivial thing.
Peace out.

[clebin]

I have made my opinion clear. I'm in no mood to argue over such a trivial thing.
Peace out.

Mate, you started the thread. And if you were being honest at the outset you would see a bunch of interesting points to help formulate your opinion, not an argument. So that answers the honesty question, then.

[Sparky]

I have made my opinion clear. I'm in no mood to argue over such a trivial thing.
Peace out.

Mate, you started the thread. And if you were being honest at the outset you would see a bunch of interesting points to help formulate your opinion, not an argument. So that answers the honesty question, then.

I made my opinion rather clear. I think it is an overpriced emulator.
Now, in the future, perhaps other makers can utilize FPGAs in a different manner.
If you read with an open mind, you will see that I have not deviated from my opinion, but I have re assessed it with the new knowledge made available to me.
No 'metaphysical' events involved...

[clebin]

I made my opinion rather clear. I think it is an overpriced emulator.
Now, in the future, perhaps other makers can utilize FPGAs in a different manner.
If you read with an open mind, you will see that I have not deviated from my opinion, but I have re assessed it with the new knowledge made available to me.
No 'metaphysical' events involved...

I will not post again on this subject, but in future don’t start a thread on a false premise and be clear up front if you’ve already made up your mind. And I think it’s poor form continuing to make fun of akeley’s use of the word “metaphysical” as he was clearly intending to bring something useful and interesting to the conversation (which I believe he did)

[1024MAK]

I can't seem to find a reliable answer either way. Does it emulate or is it hardware?

So to directly answer the question, yes and yes.

But then, consider this. In all the Sinclair made and some of the Amstrad made ZX spectrum computers, there a ULA that is emulating a bunch of 74xxx logic chips (one of the ZX Spectrum prototypes used a bunch of 74xxx series logic chips before the first ULA was made).

In the Amstrad made +2A, +2B, +3 and +3B ZX Spectrum computers, there is a ASIC that is emulating a Sinclair ULA.

In the vast majority of real Sinclair made and Amstrad made ZX Spectrum computers, there is a NEC μPD780C-01 microprocessor that is emulating a Zilog Z80A microprocessor, rather than a real Zilog Z80A microprocessor. Oh and speaking of which, the Z80 emulates instructions from the Intel 8080 microprocessor.

Happy now?

Mark

[Lethargeek]

I can't seem to find a reliable answer either way. Does it emulate or is it hardware?

So to directly answer the question, yes and yes.

But then, consider this. In all the Sinclair made and some of the Amstrad made ZX spectrum computers, there a ULA that is emulating a bunch of 74xxx logic chips (one of the ZX Spectrum prototypes used a bunch of 74xxx series logic chips before the first ULA was made).

In the Amstrad made +2A, +2B, +3 and +3B ZX Spectrum computers, there is a ASIC that is emulating a Sinclair ULA.

In the vast majority of real Sinclair made and Amstrad made ZX Spectrum computers, there is a NEC μPD780C-01 microprocessor that is emulating a Zilog Z80A microprocessor, rather than a real Zilog Z80A microprocessor. Oh and speaking of which, the Z80 emulates instructions from the Intel 8080 microprocessor.

Happy now?

Mark

Can't agree with the last part. That NEC was (a little imperfect) copy on the transistor level, and the Z80 wasn't intended to be 100% backwards compatible with the 8080. Also "instruction emulation" meant "running a software subroutine on a trapped unsupported opcode" ALAIR and never "being directly executed on different hardware"

[RMartins]

An FPGA can be made to be 100% accurate, at least for digital output regarding the original Spectrum.

However, when new requirements are added, like generate VGA or HDMI output, new Graphics modes, new CPU instructions, etc... there are further constraints being imposed on the system, which might make it impossible or at least very hard to accomplish a 100% accuracy, due to timings and other concerns inserted/imposed by the new requirements.

[Alcoholics Anonymous]

FPGAs are the future. It's hard to argue with that, but over 300 Quid for a FPGA that is utilizing emulators more than necessary... It just doesn't sit well with me.
But hey, that's just an opinion, don't take it for more than it is.

The 300 quid cost is due to case, keyboard, manual, power supply, box and 20% tax. It is very expensive to manufacture a fully custom machine on such a small scale at a commercial level. If happy with just a populated board ready for insertion into a traditional 48K case (or not), that would cost around 100 euro plus tax.

Now, in the future, perhaps other makers can utilize FPGAs in a different manner.

What manner would that be? There is NO emulator in there.

[PeterJ]

Currently out of stock [mention]Sparky[/mention], but this is the type of thing [mention]Alcoholics Anonymous[/mention] is talking about and they are 99 Euros plus tax and shipping.

https://ultimatemister.com/product/zx-n ... one-board/

This is a copy produced in agreement with the Next team.

One of the crowdfunding options for the Next was bare boards too.

[Alcoholics Anonymous]

Can't agree with the last part. That NEC was (a little imperfect) copy on the transistor level, and the Z80 wasn't intended to be 100% backwards compatible with the 8080. Also "instruction emulation" meant "running a software subroutine on a trapped unsupported opcode" ALAIR and never "being directly executed on different hardware"

The z80 was intended to be 100% binary compatible with the 8080 and as such is an 8080 emulator with extras. The NEC is reverse engineered and it's reverse engineered with errors. But it is a good clone.

In case you can't tell, he was being facetious as am I . Nothing is real - it is all emulated. The +3 is a bad 128k emulator, the 128k is a glorified 48k emulator, the 48k comes in six emulation flavours corresponding to six different circuit boards and ulas. The ttl parts are emulations of discrete resistors, diodes and transistors. The transistors are emulations of vacuum tubes. The resistors are emulations of the gunk in my bathtub.

However, when new requirements are added, like generate VGA or HDMI output, new Graphics modes, new CPU instructions, etc... there are further constraints being imposed on the system, which might make it impossible or at least very hard to accomplish a 100% accuracy, due to timings and other concerns inserted/imposed by the new requirements.

The only challenge compatibility wise that the Next has experienced is in the video because the PAL standard is not supported by modern displays (as you know). So although you have a machine putting out video just like the original machine, this has to be adapted somehow for the target display device.

VGA is actually very tolerant because it was an analog standard and displays were flexible enough to allow the spectrum's native video frame to work well unchanged. That's assuming the monitor can display a 50Hz frame which some couldn't. On such vga monitors (and rgb displays which use almost the same signal) the picture is high quality. I did say "was analog" because modern vga displays are actually digital and sample the incoming analog signal for display on digital panels. And some of them sample badly so that the spectrum video frame can come out with artifacts in the display. So the fight on vga is to accommodate displays that can't sync down to 50Hz and to try to make picture quality high on poor modern vga displays.

HDMI is a different problem as this is a digital standard and you have to precisely follow the hdmi timing in order for most hdmi displays to actually show anything. There is no bending the hdmi toward the spectrum video frame.

[Matt_B]

I'll just throw in the possibility that the universe itself is being emulated:

https://en.wikipedia.org/wiki/Simulation_hypothesis

So, er... yeah... it's best not to care about these things too deeply, so long as your platform of choice is accurate enough. And if the extent of that is merely playing games, or just doing anything with the Spectrum in software generally, you're going to be all right with a decent software emulator.

FPGAs do open up more possibilities in terms of microsecond level timings for things like interfacing hardware and accurate sound generation, although there are going to be some discrepancies with original hardware, which itself varies quite a bit between the early rubber keys and a +3, so there's still an argument for just about anything depending upon where your interest lies.

[PeterJ]

Could I ask [mention]Alcoholics Anonymous[/mention], in lay man's terms are you saying that because of the issues in emulating PAL that this is the reason why a handful (and it is a very small number in the scale of things) of programs don't work as expected.

Is the failure in some of the tests which are run to check the implementation of z80 features and other stuff due to this also, or is this due to errors made in the (programming - is it still called that?) of the FPGA?

There seems to be a view here that maybe some FPGA implementations are more accurate than others. Why is this? I notice that some cores only support one video standard such is VGA. Does this make it easier for the developer to get more accurate 'emulation'?

Thanks

[Alcoholics Anonymous]

Still worse than the best Spectrum emulators and the best Uno cores.

Really? I don't think so.

The Next can run more programs than the uno by simple virtue that the uno doesn't implement as much hardware. The +3, Pentagon 512/1024, dacs, z80 dma, etc. The uno also doesn't attempt to do hardware compatibility so it's missing an expansion bus and membrane. That's another class of programs as some were written specifically for things like the microdrives, the currah speech unit, etc. The uno is a great project but it doesn't have the same goal of being a complete spectrum. The Next is implementing everything, not just an important subset.

I'd rather you provide specific examples of incompatibilities because that is what I use to improve the hardware. It's not good enough just to make stuff up because of some suppositions in your head. I will tell you what's on my list -- I have three programs to look into out of many thousands tested.

[PeterJ]

To be fair to [mention]Pegaz[/mention], [mention]Alcoholics Anonymous[/mention] he did provide an example of Aquaplane and some other games.

[mention]Alcoholics Anonymous[/mention] - maybe you could list publicly the three titles you are looking at.

Trying to stay impartial here. It's good to discuss these things openly and in a constructive manner.

[clebin]

[mention]Alcoholics Anonymous[/mention] It's great to hear the core is still being worked on. The only area of weakness I've noticed with my Next is in loading from a real cassette deck. I've got two old tape-recorders, one of which needs a stereo-mono adapter, but the Next seems to want more volume than a classic Spectrum. So I've got them at 100% but the Next seems to want more. I'm assuming that nothing can be done at the FPGA level to mitigate this? Hopefully the Next motherboard revision will improve this a little bit.

[Sparky]

I'll just throw in the possibility that the universe itself is being emulated:

https://en.wikipedia.org/wiki/Simulation_hypothesis

So, er... yeah... it's best not to care about these things too deeply, so long as your platform of choice is accurate enough. And if the extent of that is merely playing games, or just doing anything with the Spectrum in software generally, you're going to be all right with a decent software emulator.

FPGAs do open up more possibilities in terms of microsecond level timings for things like interfacing hardware and accurate sound generation, although there are going to be some discrepancies with original hardware, which itself varies quite a bit between the early rubber keys and a +3, so there's still an argument for just about anything depending upon where your interest lies.

It's a Hypothesis, and one that I deeply believe in, strange as it may sound. Reality as we know it is not tangible, but that is getting off topic.

[azesmbog]

The +3, Pentagon 512/1024, dacs, z80 dma, etc.

Why are we walking with trump cards ??
The entry-level chip was compared slx9 ZX Uno vs slx16 Next.
Compare better with Mister with 100 thousand cells and opportunities. Personally, I would be ashamed to compare, even starting from the price several times.
otherwise, Pent512 can be started, there are no problems with ports, and +3, and z80DMA works decently in Uno, and both versions, and on both ports, and also has its own UnoDMA, which is definitely not in the next one. And so yes, protect (s).
Suum cuique

[Pegaz]

Still worse than the best Spectrum emulators and the best Uno cores.

Really? I don't think so.

The Next can run more programs than the uno by simple virtue that the uno doesn't implement as much hardware. The +3, Pentagon 512/1024, dacs, z80 dma, etc. The uno also doesn't attempt to do hardware compatibility so it's missing an expansion bus and membrane. That's another class of programs as some were written specifically for things like the microdrives, the currah speech unit, etc. The uno is a great project but it doesn't have the same goal of being a complete spectrum. The Next is implementing everything, not just an important subset.

I'd rather you provide specific examples of incompatibilities because that is what I use to improve the hardware. It's not good enough just to make stuff up because of some suppositions in your head. I will tell you what's on my list -- I have three programs to look into out of many thousands tested.

I am talked about the accuracy of the implementation of the original models, not about the amount of hardware supported by Next or some emulator.
If all the games, demos and test programs I've listed work on Next exactly the same as on the real 48k/128k Spectrum, then you're good.
I didn't even mention the four bright shades ULA effect, which, for example, supports SpecEmu and Spin, but not the Next.
You also didn't answer, how do I play e.g. Old Tower on Next via hdmi, without using xy aditional adapters and cables?
Why did you promise something you were unable to deliver ?
But that's to be expected, because you weren't even able to deliver one simple game, also promised as a stretch goal.
In reality, Next runs at a lower frequency than the original Spectrum 128k (50Hz), which can affect a lot of software, more or less.
Watch this video and say again that everything is made up..
https://www.youtube.com/watch?v=9oMyAYYFPCA