Atic-Atac Isometric Version

People are still making stuff for the Sinclair related machines. Tell us about new games and other software that runs on the Spectrum, ZX80/ZX81, Pentagon and Next.
Daren
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Re: Atic-Atac Isometric Version

Post by Daren » Tue May 07, 2019 2:36 pm

redballoon wrote:
Tue May 07, 2019 12:28 pm
Did you get along to see and try both the PC and Next demos, Daren? Sorry that I never got to chat you you if you did - there were tons of people I never got to meet.
I did, yes. Didn't have a go, just watched others on them. Mightily impressed, can't wait to get them! Played on the real Next that was there, on Baggers in Space. Looking forward to receiving mine!
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Re: Atic-Atac Isometric Version

Post by DouglasReynholm » Tue May 07, 2019 2:48 pm

redballoon wrote:
Tue May 07, 2019 12:28 pm
1 thing that’s changed already is that the original PC version was running at 30fps deliberately to make it feel more retro and the Next version was running at 60fps, so it was a long smoother. A lot of people commented on how they preferred the 60fps, so Richard has updated the PC version to run the same.
I love the fact that due to the retro gameplay and graphic style doubling the frame rate is a quick update. Really looking forward to this, the original game is only one of a few from the era I find really compelling still.
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Re: Atic-Atac Isometric Version

Post by djnzx48 » Wed May 08, 2019 12:32 am

Can the Next run at 60Hz? I thought it was still configured to 50Hz (or slightly higher). Does it have a mode designed for modern monitors?
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Re: Atic-Atac Isometric Version

Post by redballoon » Wed May 08, 2019 7:42 am

Yip, apparently so. I have no idea of the technical gubbins behind it all, though. The Next version is being being converted by Kev Brady, who is 1 of the Spectrum Next team, so he knows the hardware. The first time I saw the Next version running was on the Friday night there before the Play Expo And was informed by Kev that it’s running at 60fps.
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Seven.FFF
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Re: Atic-Atac Isometric Version

Post by Seven.FFF » Sun May 12, 2019 1:40 pm

The Next runs at both 50 and 60, over VGA, and HDMI and RGB. Only the 50 mode has accurate PAL timings. The 60 mode has accurate Timex NTSC timings.

As you might know, the Next is an FPGA machine, with reprogrammable hardware and a large FLASH memory which can hold 30 different cores to boot into. Other cores like QL, BBC Micro and Arcade machines are possible.

The main core is a super-spectrum, supporting all of the features from the classic Sinclair, Amstrad, Timex and Investronica models, plus some popular Brazilian and East European clones. There is a mechanism to turn the necessary features on and off, meaning you can boot the main core into a bunch of machine personalities matching the various Spectrum models. These personalities support standard esxDOS 0.8.6 and the three classic multiface models - virtual divMMC and multiface hardware is included in the FPGA, you don’t need to own one of these devices.

So going back to the original timings point, all things being equal, and assuming you have a capable display, it makes sense to boot most of the personalities into 50Hz mode, except the Timex models which run more accurately in 60Hz mode.

The main core can also run Paul Farrow’s ZX-80, ZX-81 and Jupiter Ace emulators, and you can configure these as boot personalities too. Strictly speaking these are not fully accurate recreations, as they run with the 128K spectrum personality settings and are still really a Spectrum doing a good job of running programs for another machine. But they’re a very nice addition, and don’t preclude the later development of dedicated cores for those machines.

Finally there’s the Next personality, which has every super-spectrum core feature enabled. It also has an extended BASIC, developed by Garry Lancaster on top of his earlier +3e work. Some of the new Next-specific features available from machine code and BASIC are a 256 colour per pixel 256x192 mode, 256 colour per pixel sprites which can extend into the border, a 320x240 tilemap mode which extends into the border, four channel 8 bit sampled sound, a fast DMA chip for copying data or feeding the DACS at regular intervals, a copper copro for making screen effects or feeding the DACS in precise timings, a new memory model that lets you put any of the Next’s 223 8K RAM banks at any of eight slots in 64K addressable memory, a unified disk API that supports +3DOS, IDEDOS and esxDOS calls all with LFN support, a new Next-oriented multiface, a fast serial port running up to 2meg baud which supports WiFi/wired connections, and lots more.

Most of these features can be used in the other classic machine personalities too, but most new games and enhanced classic games will be built for running in the Next personality.

Going back to timings, finally, not every monitor and TV out there supports 50Hz, and 60Hz timings are not always suitable for running many classic programs at, so there is also a range of six other display friendly timings from 49-59Hz. These ones preserve the authentic number of cycles per line and lines per frame for accurate timings, but do so at the expense of speeding up the master clock, so everything runs slightly faster. Out of all these display options pure 50Hz over an RBG-SCART cable will give the best compatibility for running timing-critical Spectrum and Pentagon demos.

For new games, devs can obviously pick any feature, timing and display combination which makes sense for the game. Kev will have chosen 60Hz/fps as it provides more fluid movement and runs on more displays out there than 50, and covers a larger screen area due it having less vertical lines per frame. And also because it’s an exact multiple of Richard’s original 30fps mode, which would have made the conversion much easier. I believe he will also support 50, but 60 is the showcase mode.

Sorry for the long answer, but hopefully it gives a better sense of how the Next is a layered set of compatibility-friendly features, and how the timings and screen modes fit into that.
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Re: Atic-Atac Isometric Version

Post by djnzx48 » Sun May 12, 2019 10:19 pm

Thanks for the explanation. I didn't realise that games could just pick and choose from the available hardware features. Does the CPU clock also run faster in the 60 Hz mode or have the frame timings been modified?
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Seven.FFF
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Re: Atic-Atac Isometric Version

Post by Seven.FFF » Sun May 12, 2019 11:12 pm

There are three separate controls that combine together to give an overall effect, in a quite complicated way (the curse of making a super-Spectrum that tries to support everything at once).

1) Machine timings control the number of Ts per line. There are four of these: 48K, 128K/+2 Grey, +2A/B/+3/Next Native, Pentagon 128K.

2) 50/60 controls the number of lines per frame. This is a boolean setting, and corresponds to the number of lines per frame in the Spectrum PAL and TImex NTSC models.

3) Clock speed controls the overall speed of the master clock. There are 7 of these ranged betweeen between 28MHz and 33MHz. That clock speed is divided by four to give the base CPU speed, so 28 corresponds to a Z80A running at the standard 3.5MHz.

3a) There is also an eighth clock speed control, a special HDMI compatibility setting. This adjusts both the clock (27MHz) but also tweaks the number of lines per frame slightly, moderating the result of the 50/60 setting. The purpose of this one is to get the widest compatibility with the vast array of HDMI displays out there, many of which are partially out of spec with the HDMI standard. You won't get completely accurate timings in this HDMI mode, but it doesn't affect the vast majority of games, and most people who just want to play old games on their living room TV won't notice any differences.

The most awkward programs are those that do T-state-specific demo-style tricks or run code in every available T-state in the frame. These run perfectly on RGB-SCART or VGA with (1) set to the machine type the program was designed for, (2) set to 50 and (3) set to 28MHz. However, if your display is HDMI-only, or complains about either (2) or (3), you'll have to tweak those settings and risk disrupting a timing-sensitive program, have your program run correctly but slightly fast, or seek out a more forgiving display (or external framebuffer/convertor equipment).
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Re: Atic-Atac Isometric Version

Post by Daren » Wed Jun 26, 2019 7:39 am

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Re: Atic-Atac Isometric Version

Post by Juan F. Ramirez » Mon Jul 15, 2019 8:36 pm

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