Amstrad CPCnext: Would you buy one?

[rexbeng]

Over-simplifying a bit, but if you imagine that a 16 bit machine needs twice as much memory to deal with the equivalent amount of graphics and so on, an CPC with 64k is like an ST or Amiga with only 128k, and 256k is comparable to a stock Amiga 500. In reality, without audio samples to deal with or whatever else, 128k feels about right for the CPC, 64k is uncomfortably tight and 256k is luxury.

Hm. Isn't the Amiga even more hungry than the ST when it comes to screen memory consumption? I am under the impression that it spends 64k for graphics, whereas the ST stands at 32k. Can't seem to remember where I have read that info, but by quick referencing I see that the Amiga has 4x the on-screen colours per resolution compared to the ST...

The A1000 had 256k onboard ram, so if, say, 1/4 of that is reserved for graphics, then that would make it an exact 16bit equivalent to a 464. Has anyone made any games or demos for that one and only true Amiga, lately?

[andycadley]

Over-simplifying a bit, but if you imagine that a 16 bit machine needs twice as much memory to deal with the equivalent amount of graphics and so on, an CPC with 64k is like an ST or Amiga with only 128k, and 256k is comparable to a stock Amiga 500. In reality, without audio samples to deal with or whatever else, 128k feels about right for the CPC, 64k is uncomfortably tight and 256k is luxury.

Hm. Isn't the Amiga even more hungry than the ST when it comes to screen memory consumption? I am under the impression that it spends 64k for graphics, whereas the ST stands at 32k. Can't seem to remember where I have read that info, but by quick referencing I see that the Amiga has 4x the on-screen colours per resolution compared to the ST...

The A1000 had 256k onboard ram, so if, say, 1/4 of that is reserved for graphics, then that would make it an exact 16bit equivalent to a 464. Has anyone made any games or demos for that one and only true Amiga, lately?

The Amiga can have 32 colours on screen as opposed to the ST's 16, so it's more like 40K if my maths is right. You could up that to 48K if you're using EHB (nobody does) or a Dual Playfield setup with 7 foreground and 8 background colours.

But anything for an 256K OCS Amiga is a bit rare, it's very tight for memory - a similar situation to the 464 for sure.

[Sykobee (Briggsy)]

As an owner of a Next I have learned:

 - Still don't like the Spectrum
 - It really has a poor keyboard layout (having copied the later Spectrum keyboard layout) 
 - The new features make it a new system that just happens to use a faster Z80 and have backwards compatibility with the Spectrum.

One positive is the speeding up of old games like the Freescape ones. Another is that everything is integrated and packaged into a single product.
The Spectrum Next sprites are in some ways 'super enhanced Plus sprites' - there are more, they aren't hardwired to a sprite number, and you can have more colours, but they are stored on-chip in dedicated sprite memory rather than main memory like the C64.

So I cannot see how a CPC Next would be anything but the same in the end. A new system has happens to run CPC games natively.

There is a CPC core for the next, so arguably you just need a new case and keyboard for the existing board, and some shenanigans for the hardware aspects designed for the spectrum (keyboard interface, SD card, expansion, etc) to make it work.

[cwpab]

I just accidentally found this interesting CPC Wiki topic from 4 years ago by googling ["cpc core" "spectrum next"]:

Amstrad CPC "Mini"

In particular, the message I found was this one from the user ToTO:

A CPC "Next" like a Spectrum Next will be probably able to run 80% of the existing programs properly.
While the GA/ASIC, FDC and all the CRTC will be not properly reproduced into a FPGA.

I also learned that:

- The Spectrum Next can use the Sinclair brand because Sky allowed them in exchange for donations to "the biggest charity in the UK"
- 2 year ago, a guy created something called the MSXvr, some kind of MSX next. It looks cool, but some say it feels cheap and it lacks proper video output for old TVs:

[asertus]

One minor note, VR has RBG output, apart from HDMI, and it is an emulator running on a PI, not FPGA.

[Sykobee (Briggsy)]

Over-simplifying a bit, but if you imagine that a 16 bit machine needs twice as much memory to deal with the equivalent amount of graphics and so on, an CPC with 64k is like an ST or Amiga with only 128k, and 256k is comparable to a stock Amiga 500. In reality, without audio samples to deal with or whatever else, 128k feels about right for the CPC, 64k is uncomfortably tight and 256k is luxury.

Hm. Isn't the Amiga even more hungry than the ST when it comes to screen memory consumption? I am under the impression that it spends 64k for graphics, whereas the ST stands at 32k. Can't seem to remember where I have read that info, but by quick referencing I see that the Amiga has 4x the on-screen colours per resolution compared to the ST...

The A1000 had 256k onboard ram, so if, say, 1/4 of that is reserved for graphics, then that would make it an exact 16bit equivalent to a 464. Has anyone made any games or demos for that one and only true Amiga, lately?

A1000 was pretty rare, A500 was more popular, but the 512KB memory expansions to take it to 1MB were incredibly popular because the games made use of it, and then they required it.

A dual-playfield Amiga game like Lionheart could use 80KB (320x256) but overscan was also common, so more like 100KB. But the chipset could do so much of the other work, and you still have 400+ KB for the rest of the game, and that rapidly because 1MB, and with 1MB and 880KB floppies games because graphically varied and everyone wanted an Amiga.

The Amiga was the first generation of what we call a modern PC architecture, with dedicated hardware for different functions.

The Atari ST was more of a CPC in design, perhaps even a bit more limited in some ways like screen size.

For the CPC 128KB was great, but the 64KB expansions were never cheap enough, and the games were not plentiful enough, to make getting this super-desirable, unlike the Amiga trapdoor expansions. Plus range should have been 128KB minimum.

[andycadley]

Plus range should have been 128KB minimum.

Well, the Plus range was really geared around cartridge games, where having 64K of RAM was actually quite luxurious. By the time they came out, 128K hadn't become the defacto expectation for tape/disk games (unlike on the Spectrum for example) so it's not surprising they didn't up the baseline.

[ZorrO]

Fact that Amiga system disks had a program to enable overscan and there was no such program on ST system disks, does not mean that Atari couldn't display overscan. ST demos show this as often as those on Amigas and Amstrads.

As I remember, if someone had a bare 464 at the beginning and then wanted FDD. Of course, he could buy an external 3-inch drive. But if he compared the prices, it was more reasonable to sell 464 and buy 6128 (not new of course) with the same monitor to save about 30% of price for the external drive. At the same time, not only did he save money, but he also gained better Basic and more memory. Because DDIs were really expensive. You just need to be able to read and count to find out this.

[eto]

that Atari couldn't display overscan. ST demos show this as often

On the Atari ST this was not easy to achieve. You had to program some very exact timings and then quickly switch between 50 and 60Hz. This caused the shifter to continue output from Video RAM. It took demo coders a few years until all borders could be opened and full overscan was achieved.

Later there was some hardware extension that could do this and give full overscan even in GEM. Unfortunately this did not work on the STe so I never have seen this.

[Anthony Flack]

The ease with which the CPC could deal with full overscan, and 80 column (or more) text is one of the things that separates it from the other 8 bits (well apart from the BBC, naturally). 

So, maybe you need two or four times more graphics memory for an equivalent 16 bit machine, and for audio it's going to be WAY more once you start using samples. Funny thing is the actual game code still ought to not be much more than a CPC game... you can pack a whole lot of ASM into 16k.

SUCH a shame they fumbled the GX launch as I would have loved to see more games using the cartridge format with all that ROM space and Vespertino-sized sprite banks. I was trying to think of the kinds of games you could make that took advantage of the GX's comparatively large amount of RAM for a console, but wasn't compromised by its lack of save ability. I thought maybe some kind of roguelike? Something with a large procedural map and lots of items to keep track of, but with a short game loop and lacking the long-term permanence of a campaign strategy or RPG. It's a thought.

I've also been thinking about the ol' Bomb Jack with regards to cartridge format. Right from the beginning I knew I wanted to make it disk-based because keeping your high scores is important; it's a score-based game. I've got an older build running on my real 6128 where you need to get at least half a mil just to get on the score table now, and I've been reluctant to update it since I don't want to mess with my high scores! I might just have to patch them in... maybe I should include a high score file merging utility...

But the game would be well-suited to a Plus upgrade. I could probably do away with two of the screen buffers if everything was done with sprites, and all the compiled sprite data would be replaced with Plus sprite data, and it might even fit in 64k of RAM then. Maybe. But I still think I'd go for a disk version first just for the high score saving. Maybe you could do a cartridge game that saves files to disk, or M4 drive or whatever, but that's fiddly and still no good for the GX.

It's funny how Amstrad already supplied us with the CPC Next with the Plus machines, as well as the CPC Mini with the GX. Two years too late, or thirty years too early?

[ZorrO]

I think in 1990, at a similar price to GX4000, was available Sega Master System, which provided dozens of colors at once on  screen in small pixels, and dozens of great games. GX with its wide pixels and a few boring games had no chance against SMS. Not with such price. A budget machine at a premium price.

[McArti0]

Old Bomb Jack needs a patch.
When you take the bonus, the bombs show 2x200, 3x200, 4x200 points but only one 200 is added to the result.

Amstrad Next should get Z80H 8MHz like Amiga 1200 14MHz and Atari MegaST 16MHz.

[Anthony Flack]

I think the Plus probably has a slight edge over the SMS in graphics, but it has almost no games. And quite literally NO games in many shops since the launch was so badly botched and the cartridges weren't ready in time, and when they did arrive they were frequently mislabeled with the wrong game.

The SMS pixels are not so small; 256x192 compared to full overscan Mode 0 resolution of 192x288 on the GX. Each pixel on the SMS is three PAL pixels wide compared to CPC mode 0 pixels which are 4 PAL pixels wide. Mode 1 pixels are smaller than SMS pixels. And the 64 colour palette is an improvement on the original CPC, but not by much.  You definitely notice the extra colours on the Plus.

[Anthony Flack]

Old Bomb Jack needs a patch.
When you take the bonus, the bombs show 2x200, 3x200, 4x200 points but only one 200 is added to the result.

Amstrad Next should get Z80H 8MHz like Amiga 1200 14MHz and Atari MegaST 16MHz.

I never knew that. Most of the scoring mechanisms in old CPC Bomb Jack are quite mangled though, or missing entirely. In the arcade game they are finely balanced. That was really the thing that I wanted to correct with the new port.

[Anthony Flack]

One thing that was really noticeable on the Amiga was with all the extra memory, a drive speed that was perfectly adequate for a 128k machine becomes quite painfully slow when playing 1Mb games filled with lots of pointless splash screens (insert side 3 now).

[ZorrO]

Anthony Flack - You right, SMS have terrible games: 

[Anthony Flack]

I never said anything about SMS games. I said the pixels size is larger than you might think and the colour palette not much better than the original CPC, and the GX probably has the edge when it comes to graphics.

I can tell you that I have a copy of every one of the games mentioned in that video. 

[angry]

The ease with which the CPC could deal with full overscan, and 80 column (or more) text is one of the things that separates it from the other 8 bits (well apart from the BBC, naturally).

So, maybe you need two or four times more graphics memory for an equivalent 16 bit machine, and for audio it's going to be WAY more once you start using samples. Funny thing is the actual game code still ought to not be much more than a CPC game... you can pack a whole lot of ASM into 16k.

SUCH a shame they fumbled the GX launch as I would have loved to see more games using the cartridge format with all that ROM space and Vespertino-sized sprite banks. I was trying to think of the kinds of games you could make that took advantage of the GX's comparatively large amount of RAM for a console, but wasn't compromised by its lack of save ability. I thought maybe some kind of roguelike? Something with a large procedural map and lots of items to keep track of, but with a short game loop and lacking the long-term permanence of a campaign strategy or RPG. It's a thought.

I've also been thinking about the ol' Bomb Jack with regards to cartridge format. Right from the beginning I knew I wanted to make it disk-based because keeping your high scores is important; it's a score-based game. I've got an older build running on my real 6128 where you need to get at least half a mil just to get on the score table now, and I've been reluctant to update it since I don't want to mess with my high scores! I might just have to patch them in... maybe I should include a high score file merging utility...

But the game would be well-suited to a Plus upgrade. I could probably do away with two of the screen buffers if everything was done with sprites, and all the compiled sprite data would be replaced with Plus sprite data, and it might even fit in 64k of RAM then. Maybe. But I still think I'd go for a disk version first just for the high score saving. Maybe you could do a cartridge game that saves files to disk, or M4 drive or whatever, but that's fiddly and still no good for the GX.

It's funny how Amstrad already supplied us with the CPC Next with the Plus machines, as well as the CPC Mini with the GX. Two years too late, or thirty years too early?

I reckon an arcade perfect Bomb Jack would be possible on the Plus. The backgrounds could be in mode 1 with a bunch of raster splits - you can change a colour every 32 pixels (with an 8 pixel accuracy) horizontally in mode 1. It would burn through CPU time but with the sprites there should be enough CPU left for 50hz.... probably.

What do you think? "Easy" - right?!

[eto]

What do you think? "Easy" - right?!

I am SO looking forward to your port :-) 

[Anthony Flack]

I suspect that transferring data to and from sprite memory in the ASIC may eat up too much time to be able to also do 208 lines of continuous raster splits on top. For everything else, you'd just about make it.

The other problem with trying to do the background that way though is you have all these annoying bombs and platforms with a gradient on them, all over the image. They are going to hog three of the four colours on most lines. OK if they were on a separate layer... but they're not...

[andycadley]

I reckon an arcade perfect Bomb Jack would be possible on the Plus. The backgrounds could be in mode 1 with a bunch of raster splits - you can change a colour every 32 pixels (with an 8 pixel accuracy) horizontally in mode 1. It would burn through CPU time but with the sprites there should be enough CPU left for 50hz.... probably.

What do you think? "Easy" - right?!

Not quite. Split rasters on the Plus are complicated by the fact each palette register takes two bytes. Thus changing one colour is not an atomic operation and the transition will be visible on screen. Maybe you can get around that if you're careful on colour selection to some degree.

The bombs could maybe be multiplexed sprites, but then you're racing the beam trying to do colour splitting and sprite multiplexing. No easy feat, for sure.

[ZorrO]

CPC-Next ?? 

Source: http://androidarts.com/Amiga/SBC.htm

[Anthony Flack]

Multiplexing the bombs would be a hell of a thing. There can be six or more on a single line. Maybe if that's all you had to draw, but there is also the player, up to seven chasers, two birds, a power ball and a bonus coin that can all be on screen at the same time. And all potentially on the same line as those six bombs. Plus there's effects, and the scores left behind by collected bombs.

[Anthony Flack]

I mean, don't think I haven't thought about it. I've thought about splitting colours in the background, and I've thought about multiplexing the bombs... I want to believe!

I think multiplexing the bombs is just too much and they will have to be printed to the background, or else expect some major sprite flickering to occur. I also would want to use two sprites to add extra colours to the top HUD. I think some limited colour splitting could be applied in mode 1, but there would only be one floating colour and you'd be limited to a few simple line splits. it's an open question whether that would look better or worse than a mode 0 background with accurate colour. The background is not so bad, but it is a bummer to see the bombs rendered chunky, because then you can see they are rendered to the background. There's enough sprites left over that the little 200 points indicators left behind when you collect a bomb could be sprites. All the other sprites should look nearly arcade perfect.

The Master System, since that's our benchmark, has enough sprites to cover all the moving objects, same as the GX. But they'd flicker more often with only four per line. It would also not have enough tile memory to display the backgrounds, and it would blow up the tile memory even worse if you hoped to print the bombs on top without square borders. Worse is that it doesn't have anywhere near the vertical screen resolution and might have to use a vertical scroll like they did for Ms Pac Man. I love the SMS but it is quite stubby, especially in PAL mode.

Also the AY sound chip in the CPC is the same as the arcade board (which admittedly does have three of them. Heck they sounded pretty great in Gyruss when they stacked five of them together). So ok, maybe your hypothetical CPC Next could have double sound chips. But even just one AY gets pretty close to the arcade sound and is better than the SN chip in the SMS which has no bottom notes.

[GUNHED]

BTW: About CPC and RAM-Banking you did forget to mention some feature...

8 KB of expansion RAM can be banked in at every multiple of &2000, this enhances banking quite useful! No other computer has that nice little gem. That's what I call Nova-Blast!