SPECTRA Advanced Graphics

[Fruitcake]

I have always stated that I would be interested to make a 128 compatible version if there was sufficient demand.

I distinctly recall you saying otherwise.

You might recall that but you would be wrong.

It is not the same as people repeatedly making false statements about ULAplus and it is disingenuous of you to suggest otherwise.

I wasn’t aware LCD had repeatedly made false claims about ULA+...

And I fail to see how writing something that isn’t true about ULA+ is any different to writing something that isn’t true about anything else. People might make mistakes and misunderstand things, but that does not imply it is necessarily deliberate.

as I understand it the device is designed for a 48K machine.

for the existing device you'd either have to modify the Spectrum, or the device, no?

Yes, SPECTRA only works on a 16K/48K Spectrum, but the principle could work on a 128K machine. You original statement could be interpreted as implying the principle could never work on a 128K Spectrum.

I'm entitled to my opinion.

Indeed you are, and I’m not going to try and convince you otherwise. I respect that is your view. But LCD is entitled to his opinion also and he simply stated that in his view SPECTRA was better for him. He didn’t say in what way or for which application, but there are things SPECTRA can do that ULA+ cannot and you didn’t know if these were the aspects he had in mind because you didn’t bother to ask him. You just told him why he was wrong.

• RGB SCART connectivity (with all necessary signalling voltages)
  No arguments there. Not many modern televisions can take the fake PAL signal from the Speccy but with SPECTRA they will work providing they provide a SCART input. Excellent job.
  
• Sound output via SCART
  Given that SCART provides an audio carrier I would expect this. If you added a virtual AY chip with stereo output it would be even neater.
  
• Additional colours and colour resolutions (32 modes in total)
  The Timex machines have been available since 1983 and include three screen modes. These machines were quite widely available yet in the last 30 years almost no software has been written to use them. In Russia they developed 16C mode with per-pixel colour. I think the total number of titles has recently exceeded single figures. I'm sure it was fun to do from a development point of view but I will be stunned if more than a handful of titles are ever released for one of these modes, let alone all 32. Until you get emulator support in a mainstream Windows-based emulator, developing for SPECTRA is a drag. And then you've got to fight against the "if it's not attribute clashy it's not a Speccy" crowd. I'm really not knocking what you've done, I'm just suggesting you should have realistic expectations about how much software support you're going to get.
  
  
• Additional border colours and effects
  As above.
  
• Screen buffering to avoid flicker (double screen buffers)
  There are other ways of avoiding screen flickering besides double buffering. In practice the double buffer on the Timex and the 128 didn't get used very often because the overhead of copying the screen to the buffer kills the frame rate.
  
  
• ZX Interface 1 compatible RS232 socket
  Certainly useful with your programmable IF2 carts, but I can't think of many other applications.
  
  
• Kempston compatible joystick socket
  Always a welcome addition. You can disable it though right? Having two Kempston interfaces daisy chained can cause problems, especially with DivIDE+.
  
  
• Optional onboard EPROM facility
  I take it that' replicates the functionality of your programmable IF2 carts.
  
  
• Optional ZX Interface 2 compatible ROM cartridge socket
  A nice touch.
  
• ZX Interface 1 compatible ROM paging mechanism for use with the ROM facilities
  Handy if you've got some kind of IF1 file system support, but possibly not so much use with divIDE or Spectranet.
  
  
• Reset button
  
• Full width rear expansion bus with gold plated connections
  Very nice. ThHroughports are always appreciated.
  
• Configuration switches to ensure full I/O compatible with all existing Spectrum devices

Thanks for your views on these facilities. Not everybody is going to use them all but they are simply there should they want to...

I'm just suggesting you should have realistic expectations about how much software support you're going to get.

But no one has claimed there will be massive support. I’ve never said that. I would be very surprised if there was such support for any computer that is over 30 years old. My aim is that SPECTRA gives people the opportunity to play their favourite games on their new TVs using real unmodified hardware for years to come. If there are a handful of devoted developers out there that want to make new games then the extra display modes are there should they wish to exploit them.

• Configuration switches to ensure full I/O compatible with all existing Spectrum devices

Impossible. Even if you kill all of the I/O and pass all the signals out of the back without changing them, just by adding length to the lines you will render some interfaces unusable.

I wrote ‘full IO compatibility’ not ‘full compatibility’, i.e. no IO address conflicts. If a user has a preferred Kempston joystick interface then the one on SPECTRA can be disabled. If they have an Interface 1 connected then the RS232 on SPECTRA can be disabled. If they have one of the few devices that conflict with the IO port for the display modes (Kempston Mouse and SpecDrum to my knowledge) then the display modes can be disabled (why would they need the extra modes for existing software to drive these devices anyway?).

Of course I can’t guarantee SPECTRA will work with all other interfaces. There are electrical issues as you say, such as power, noise, timing. There are also physical limitations, e.g. it is not possible to plug an Interface 1 in the back of an Interface 2, or practical to plug an Interface 1 in the back of a DivIDE. But that it not what I claimed.

If you want to switch to using I/O in that range then it's not too late.

Thanks, but I’m happy with the approach I’ve used.

So ULA+ has 4x1 Attributes mode too?

No, because that mode takes too much RAM and too much CPU to make much use of.

So even for a graphics editor or a word processor it wouldn't be useful?

I'd be shocked to see a new graphics editor or word processor released for the Spectrum.

My point was, as I’m sure you understand, that you cannot simply dismiss a mode out of hand because you don’t know all possible applications it might be used for. Even if used for games, not all have fast moving sprites and animation that require as much CPU power as can be thrown at them.

Not a 384 line display?

Yes you are correct. A typing mistake on my behalf.

And of course a CPU routine could be used to switch between the display modes midway through each TV frame to generate a hybrid mode display.

Yeah, did that on the Timex over a decade ago:

Not claiming the technique is new, just stating it is possible with SPECTRA to highlight that like ULA+ it also has untapped potential...

You have to be careful with that when using devices like Spectranet, or other things which also use a shadow ROM.

Unfortunately some devices take the route of deliberately preventing other interfaces co-existing should they also contain a ROM. They assume they will be the only device connected with a ROM. SPECTRA does not make such an assumption.

The DivIDE should ideally check the ROMCS line on its rear expansion bus and keep quiet if something behind it attempts to use the ROM address space. That is how the ROMCS line is supposed to work. The DivIDE takes the approach of not passing the MREQ line through and thus forcibly stops another device seeing a ROM address access. Therefore the DivIDE never has to worry about devices behind it (devices in front of it are a different matter). But this approach also prevents techniques such as memory mapped IO working, or even an original Interface 2 ROM cartridge working alongside the DivIDE. If devices were designed not to assume they had exclusive access to the ROM address space then compatibility would be increased.

If SPECTRA is connected behind a DivIDE then it cannot see the RAM accesses which it needs to monitor. The DivIDE should have no business filtering out RAM accesses otherwise it can even prevent a device without a ROM from working. As a result, SPECTRA needs to be connected in front of the DivIDE, or alternatively the missing MREQ line can be added to the DivIDE.

But a nice consequence of plugging SPECTRA ahead of a device such as the DivIDE is that SPECTRA can be fitted with a customised version of the Spectrum ROM (e.g. fixing all bugs) and will override the Spectrum’s internal ROM. The DivIDE will then override the SPECTRA ROM, thus the user experiences a bug free BASIC ROM with DivIDE functionality.

Basically if you want to work with modern storage you're limited to a single BIOS ROM.

Only because of the design choices made for those devices. Create new storage devices and that issue can be overcome...

It's a forum. I don't spend hours composing my posts. I thought it was implicit.

I thought it was implicit that LCD was simply stating his preference for SPECTRA for his particular needs but you didn’t. So I think being precise helps remove ambiguity and scope for misinterpretation.

It wasn't a dodge.

My point was that the availability of a video mode doesn't translate into software releases.

And that is a fair point, but LCD’s point (which I also thought was implicit) was that adding support for the Timex modes does not open up a huge resource of new software to use. How many titles there are available for SPECTRA is irrelevant to this argument.

I have not gone out of my way to belittle SPECTRA.

This is the first time since then that I recall writing anything about it, and only because I was annoyed at LCDs description of SPECTRA as being "better" than ULAplus.

But that is just his opinion. Isn’t he entitled to an opinion that differs to yours? If he originally said ULA+ couldn’t do something that it could then correcting him would be fair enough. You’ve described SPECTRA display modes as

worse than ULAplus in every single respect.

How is that phrasing any better than LCD’s?

I was annoyed at LCDs description of SPECTRA as being "better" than ULAplus. To my mind they are different things.

Its extended colour scheme is worse than ULAplus in every single respect.

Then why keep comparing then?

I'm not pushing ULAplus on anyone, I'm just trying to correct some common misconceptions.

Nothing wrong with correcting misconceptions. It’s just that LCD did not originally state anything specific about ULA+, only that he preferred SPECTRA. Therefore his original statement that you took offence at did not present any misrepresentations, only an opinion.

I still think SPECTRA would have had a bigger market if you'd supported the ULAplus standard.

Maybe but if people just want to get a clearer, dot-crawl free picture on their TV then they don’t need any new colour modes, SPECTRA or ULA+. And as you have said trying to get people to develop for new display modes is difficult; most people simply like to play the games they remember.