Z80 big family

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By TomH

Champion (291)

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08-02-2018, 21:36

Dear Timmy, I would consider not further engaging; there's no good outcome you can realistically hope for.

I agree that throughput is the obstacle that obstructs various kinds of games, but am prone to believe that as an outlier in that regard, the MSX would probably have always drawn the short straw if treated as a secondary platform, whether the dominant thing had been the Spectrum or anything else. For my money the Japanese games, which often treat it as the primary platform to be designed around, are the most well-presented.

Maybe porting from the C64 would occasionally have been better, but that platform seems to be very highly invested in scrolling, so maybe not.

By PingPong

Prophet (3181)

PingPong's picture

08-02-2018, 22:30

TomH wrote:

Maybe porting from the C64 would occasionally have been better, but that platform seems to be very highly invested in scrolling, so maybe not.

porting from c64 to msx do not achieve the same quality because VIC-II outperform MSX1 VDP in every aspect, color, hi-res , support for raster effects, and expecially hw sprites, that are a lot flexible on VIC-II.
It is very difficult to see a port to msx1 of a c64 game that is better on msx...

By JohnHassink

Ambassador (5380)

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09-02-2018, 01:06

Timmy wrote:

First, the VDP really is very slow and restricted and really badly designed and therefore porting Spectrum games is really hard.

It is? I always (apparently wrongly) assumed that it was relatively easy because of both VDPs having a lot of similarities, and that was one of the reasons for the flood of Spectrum conversions on MSX.

By TomH

Champion (291)

TomH's picture

09-02-2018, 01:15

It's easier than to the CPC, that other platform that suffers from too many extraordinarily lazy Spectrum ports, as it provides a similar-but-more-detailed display mode; without necessarily being able to speak for Timmy I would guess that 'slow and restricted' in the sense that if you come at it thinking the CPU has time to plot the same number of pixels per frame as a Spectrum at the same granularity, you're going to be disappointed by the speed and therefore consider yourself restricted in what you can achieve.

You really need to switch to thinking in terms of hardware sprites, composing things in tiles and uploading resources ahead of time.

I don't know if you're also a programmer, but an approximate analogy might be the effort of switching from programming games for DOS, where the frame buffer is just an area of memory, and programming them for DirectDraw (as was) or any other GPU-accelerated framework. If you think you can still efficiently plot pixels with the CPU, you're in for a shock. You need to get into the mindset of upload and manipulate.

It's then just unfortunate that 'pixel scroll' isn't a supported manipulation.

By PingPong

Prophet (3181)

PingPong's picture

09-02-2018, 01:39

JohnHassink wrote:
Timmy wrote:

First, the VDP really is very slow and restricted and really badly designed and therefore porting Spectrum games is really hard.

It is? I always (apparently wrongly) assumed that it was relatively easy because of both VDPs having a lot of similarities, and that was one of the reasons for the flood of Spectrum conversions on MSX.

there is not similarity.
the only thing that is similar is the screen resolution. Even the colour clash is different.

By Grauw

Enlighted (7791)

Grauw's picture

09-02-2018, 02:13

JohnHassink wrote:

I always (apparently wrongly) assumed that [porting Spectrum games] was relatively easy because of both VDPs having a lot of similarities, and that was one of the reasons for the flood of Spectrum conversions on MSX.

It’s easy because the Spectrum graphic capabilities are a subset of screen 2. So no new graphics necessary. In principle, once you write a routine to output a RAM buffer in Spectrum format to MSX VRAM, converting to screen 2 memory layout on the fly, you can easily convert a lot of Spectrum quickly.

However, of course that routine takes time to execute, which slows down the game. A proper conversion would write directly to VRAM or at least write to a RAM buffer in an MSX-ready format, use sprites to benefit from their hardware acceleration, tiles, etc. Which would still be quite a lightweight port compared to what they would have to do for other system with quite different CPU and VDP architectures (different resolutions, etc.). But few businesses cared to invest in that it seems.

For ports to other platforms like C64, they would be forced to put in a lot more effort and rewrite a lot of code and graphics due to their differences. But for MSX the cheapest way would often be to take the Spectrum version and use the above mentioned approach, so our relative similarity turns out to work in our disadvantage in that regard.

On the other hand, without the similarity a lot of games may simply not have been released on MSX at all, so maybe we didn’t really get the short end of the stick after all.

By eimaster

Master (218)

eimaster's picture

09-02-2018, 03:10

I want to port SVI-3x8 games to MSX like Spectron. What should I know? Or what tools or utilities can help me do it?

By TomH

Champion (291)

TomH's picture

12-02-2018, 15:35

I'm well out of my depth to comment on this, but as chat has otherwise gone silent: I feel like now that OpenMSX supports SVI computers, the shortcut to porting would be to load the game into OpenMSX, set a breakpoint on VDP accesses and use that to find code that needs adaptation rather than follow a traditional forward reading disassemble approach?

I have to admit to being an SVI dunce; I'd hope that you're just looking to tweak a few port numbers — that its brief life means there's nothing out there that extends the memory map or exploits any oddities in the one machine that one couldn't safely extrapolate to a cross-manufacturer standard like the MSX.

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