zub

Incidentally, you can see the effect of a bounded search in action in Manic Miner (albeit that the data picked up falls beyond the intended range of the bounded search, if you insert* an attribute value into a cavern layout which doesn't match with any of the attribute or graphical bytes in the cavern's cell definitions.

 

(*e.g. Manually via the Hex Editor, not in JSWED's GUI.)

 

What happens is that when the CPIR loop comes to an end having failed to find a match after searching through the range of addresses #8020-#8067, HL is left pointing at the next address in the cavern buffer: #8068. The next eight bytes - #8068-#806E (various parameters which define Willy's state upon entry to the cavern) and #806F (which defines the conveyor direction for the cavern) are then interpreted as graphical bytes to draw the pixel pattern of the errant cell.

Thank you for sharing that: I had not actually bothered to check what was there in memory! Given that the graphic drawn will vary, that makes the case for saying it's less of an issue if an unbounded search is used. From a computer science PoV, I still really dislike that sort of code, but I suppose I must admit that on the Spectrum, it wouldn't be much of a practical concern.

For reference, Norman Sword's fix for the CGB (as part of a more fundamental rewrite/optimisation of the Room Expansion routine) is listed here:

 

http://jswmm.co.uk/topic/496-source-code-for-jsw/?p=11166

 

It involves a bounded search.

 

(P.S. My tablet attempted to autocorrect that to "a bouncer search", which sounds like a plotline from Neighbours during the 1980's.)

Norman Sword

Stuart, if this were the Manic Miner game engine under consideration, then an unbounded search could indeed lead to a search well beyond the intended range of data. Because the data in stored in MM in such a way that each cell of the screen layout could potentially be populated with any attribute value between #00 and #FF.

 

However, in Jet Set Willy, because of the way that the room layouts are compressed/expanded, each screen cell can only hold one of the six attribute values defined in the table of room cell definitions. So by the time the program comes to execute the CPIR code (or any of the fixes put forward here to replace it), I don't believe that an unbounded search will take place in practice in the JSW engine.

That seems reasonable. However, it may worth noting that mine was a fix for both MM and JSW, and I wanted to avoid unnecessary differences between the MM version of the fix and the JSW version.

It did occur to me that JSW might be immune for the very reason that you state, but given that the JSW engine tends to be full of interesting

The update on Github wasn't transferred to a disassembly update until the following January:

https://skoolkid.github.io/jetsetwilly/reference/changelog.html#20160117

Ah, I guess I had no way of knowing, then! Looking back, I included an acknowledgement of SkoolKid

Okay, so it turns out that SkoolKid committed his fix in the SkoolKit disassembly about a month before I posted my fix! I

BTW, as it has been asked about: it

Jonathan (J. G. Harston) is acknowledged in the Credits section of SkoolKid's disassembly. Since I believe his fix has been available online for a long time (before SkoolKid's otherwise great disassembly was created), if the two solutions are similar (or the same, perhaps?), I wouldn't be surprised if Richard (SkoolKid) had actually copied Jonathan's solution.

Sorry to revive an old thread, but are you sure about that? I tried my best at the time to search for an existing fix, and would feel rather rotten if it turns out I overlooked someone else

regarding the topic I have an editor for the Dragon machine :)

Cool! Is there a disk image of this on the net that we can play with?

It seems Dragon disks use MFM so should be dumpable with a PC (although admittedly an old one) with the right software.

The floppy formats seem to be the same as those used for the PC, so perhaps these will work in some USB floppy drives, although I won

For anyone who

I

I have. :)

 

It does play OK.

 

Its meant to have 60 screens instead of 20 IIRC. Those being two extra 'sets' of levels. However the cheat to activate them does not appear to work on emulation. :unsure: I'm not sure if this is the way the emulator (more accurately the PC keyboard I guess) is read or something else. :)

Hmm? I thought you just pressed 1, 2 or 3 at the title screen to choose a level set.

The game lacks the charm of the Spectrum version in my opinion. I really dislike the conveyor belts, in particular. I

I

Just to say, I

I just had a look at that, the crucial jump seems to be at 10:17 (after which you abandoned trying to get the top left item in Out on a Limb). Did you try the trick of jumping up on the spot then holding down left and jump simultaneously before he lands, to execute a left jump without first stepping forward by one pixel?

Yes. Believe me, I tried it a million times too. :-)

I have uploaded to YouTube a walkthrough of JSW for the MSX based on Geoff Neil

I am still intrigued by the infamous Room 47, and why Smith created such a room, to the extent of having it as one of the numbered screens. You can drop from it into Conservatory Roof, but you cannot access it by jumping up from that screen (using the long jump poke). which makes me wonder if there was any other way of accessing it from another room.

 

Does anyone else have any info on this room? 

The screen consists entirely of background tiles, and the graphic data for the background tile is blank (with black-on-black attributes), but parts of the room data actually contain code remnants. Take a look at the SkoolKit disassembly.

I was going to say I did not recall that. He's not been active for a while though it seems :(

 

Lets quote it anyway as some have 'email me when someone quotes my posts' enabled...

Oops, bad of me, I

Out of curiosity, do we have a place to migrate discussions of the 

Played the msx version for the first time this morning,it is okay to be honest although slightly slower than the speccy verison and a little clunky (not smooth),I did notice a few different things as I explored such as there being no flash function on the scenery unless I was mistaken.

Sorry for the delay!

You were not playing the truly awful HudsonSoft Bee Card version, I trust?

Else

To be honest, I imagine that for some screens, the items were planned to begin with, but in other cases, the items have been sprinkled on towards the end of development. I can definitely believe Matthew Smith was fed up with it at that point, and that

It always seemed to me that perhaps there was something missing in Ballroom East although would think perhaps it would go on the platform above, meaning you

To be honest, I

I guess we agree on Swimming Pool. I was sure other screens had white ropes, but apparently not! Cyan seems the least intrusive colour. On the Spectrum, if we use the same attributes as the MSX, the engine can

I just found this post by Cameron(e) Else, which states 

I just found this post by Cameron(e) Else, which states