Jet Set Willy I wonder if this could be done...would like to try

[The Usotsuki]

A few hours ago, I saw some video play of a port of Jet Set Willy to the Tano Dragon, and it got me thinking.

 

We know the Tano Dragon, being a modified Tandy Color Computer, has similar graphical capabilities to the Apple ][.

 

We know the Commodore 64, which also got a port, has a CPU of equivalent power to the ]['s.

 

I'd prolly pitch in as much as I can if someone else wanted to try, though I'm a horrible game programmer - but I'd like to see if Jet Set Willy could be pulled off on the ][. I bet it could.

[TMR]

We know the Commodore 64, which also got a port, has a CPU of equivalent power to the ]['s.

But it also has hardware sprites and JSW on the C64 is using them for Willy, the enemies and even static but animated objects like Maria or the toilet. i'm not saying it's impossible, just that the C64 version can't really be used for illustrative purposes in that way. (And if i had an interest, i'd start at Manic Miner personally... =-)

[The Usotsuki]

The ZX Spectrum doesn't have hardware sprites, iirc.

[TMR]

The ZX Spectrum doesn't have hardware sprites, iirc.

No it doesn't, but again that doesn't work for demonstrative purposes because the Spectrum's CPU is a Z80A pulling 3.5MHz which gives it about twice the overall processing power.

 

The closest thing i could think of at this time in the morning before the caffeine kicked in was the Oric 1, which is 6502-based at 1MHz with 48K of RAM and no hardware sprites; there isn't a port of Jet Set Willy for it but they did produce a version of Manic Miner - since that works, JSW should be possible on both machines.

[The Usotsuki]

I've heard mixed comments about how the 6502 and Z80 rate clock-for-clock, but generally I've heard that a 1 MHz 6502 holds its own against a 3.58 MHz Z80.

 

I'll give Manic Miner a look-see later.

[GroovyBee]

Personally I'd have a buffer that contained enemies copied from RAM and then pre-shifted. Mostly the bad guys don't overlap (but its a long time since I played). So you could just do block copies of the pre-shifts into place. If they overlap you'll need to work out the best way of handling that on a per screen basis. Once you get a fast sprite handling routine you'll be good to go. The baddies don't move every 60Hz frame either. So you have a whole frames worth of time to get everything done in.

[The Usotsuki]

I've heard that's a good idea too.

 

For what it's worth, there's a remake on Linux written in C (for both MM and JSW), which may provide enough pseudocode to use as a base. And I could always test out the engine with an Arcade Board or EZCI (which are much more like the Spectrum's video hardware - witness all the cheap Spectrum-to-MSX ports out there) before trying to tackle a native mode port.

[JamesD]

No it doesn't, but again that doesn't work for demonstrative purposes because the Spectrum's CPU is a Z80A pulling 3.5MHz which gives it about twice the overall processing power.

 

The closest thing i could think of at this time in the morning before the caffeine kicked in was the Oric 1, which is 6502-based at 1MHz with 48K of RAM and no hardware sprites; there isn't a port of Jet Set Willy for it but they did produce a version of Manic Miner - since that works, JSW should be possible on both machines.

The speed difference between a 6502 and a Z80 depends on what you are doing and heavily on the architecture of the target machines.

What I looked at in speed difference varied a lot.

I thought 2.2 to 2.5 times the speed seemed to be a fairly accurate comparison for general code.

I've seen greater differences on select code snippits but there was a little bit of cheating going on (leaving out some required code) so be cautious of claimed huge differences.

Once you start unrolling loops, keep data within 256 byte ranges, etc... the 6502 gains on a faster clocked Z80 though.

 

The Apple has no wait states when accessing video RAM but the Spectrum does.

On the Speccy you slow down whatever you are drawing if a screen update takes too long.

On JSW there are few enough sprites this shouldn't be an issue but on something like Elite it is.

It was faster to draw to a buffer and then copy it to display which is a lot more work.

 

Other than the graphics being very different, the Oric is roughly equivalent to an Apple II with a Mockingboard that only has 1 AY chip.

It's a pretty slick little machine but I wish they had offered an easier to use graphics mode.

Edited May 21, 2015 by JamesD