Andreas Gustafsson's Blog

Z80 optimizing

2009-08-13T17:46:00.002+02:00

It's funny how you can look at some code and think, yeah, that's as good as it gets, then suddenly you get a bright idea and realize that - no, it wasn't!
I am working on yet another little demo at the moment, on a system that uses the Z80 CPU (not saying any more than that at the moment! :))
For one of the effects, a single iteration of an unrolled loop looked like this:


exx          ; 4
ld    a,(bc) ; 7
inc   bc     ; 6
ld    l,a    ; 4
ld    d,(hl) ; 7
ld    a,(bc) ; 7
inc   bc     ; 6
ld    l,a    ; 4
ld    a,(hl) ; 7
sla   a      ; 8
or    d      ; 4
exx          ; 4
ld    (de),a ; 7
inc   de     ; 6
             ---
             81 T-STATES

That was my first, off-the-top-of-my-head implementation made a couple of days ago. I was convinced that it was possible to do much better, but I couldn't figure anything out.

Then yesterday I made some progress and came up with this, by swapping around some registers and realizing that in this case rlca worked just as well as sla a and saved 4 T-states:


exx          ; 4
ld    c,(hl) ; 7
inc   hl     ; 6
ld    a,(bc) ; 7
ld    d,a    ; 4
ld    c,(hl) ; 7
inc   hl     ; 6
ld    a,(bc) ; 7
rlca         ; 4
or    d      ; 4
exx          ; 4
ld    (de),a ; 7
inc   de     ; 6
             ---
             73 T-STATES

I sat and stared at the solution for a quite long, and thought, yeah, that's optimized!
But today I discovered that by rearranging my data and using the nice ex de,hl instruction, there were cycles to be saved, and I ended up with this:


ld    e,(hl)   7
inc   hl     ; 6
ld    a,(de) ; 7
rlca         ; 4
ld    e,(hl)   7
inc   hl     ; 6
ex    de,hl  ; 4
or    (hl)   ; 7
ex    de,hl  ; 4
ld    (bc),a ; 7
inc   bc     ; 6
             ---
             65 T-STATES

So NOW it must be as optimized as possible, right? :)

2008 in retrospect

2009-01-01T22:31:00.003+01:00

Yes, my blog has been woefully neglected the past year, so I better start this year a bit more productively with a look back at 2008.

Major things for me during 2008 was first of all that I added several nice items to my collection of old 80ies computers:

Commodore Plus/4

Commodore VIC-20

Philips NMS-8245 (MSX2)

Atari 130XE

Commodore 64 (old bread-bin model, I had a C64C before)

I also had a very productive year on the demoscene (after a bit slow start the first months), releasing more stuff than I have ever done any previous year:

407566 - C64 onefile demo, released in April

Very Much Useless - Sega VMU demo, winner of mixed compo at LCP2008 in August

Pseudocode - C64 demo, 3rd in C64 compo at LCP2008 in August

126b - VIC-20 intro, released in August

Ancient School - VIC-20 demo, winner of Sundown oldschool demo competition in September

Invasion of the big pixels - MSX1 demo, 2nd place at the Grep White demo competition in December

I'll be very pleased if I can keep the same tempo this year!

BFP 2007

2007-08-06T00:08:00.001+02:00

A week has passed since the Big Floppy People 2007 demo party, and I have forgotten to write about it!

It was a nice event, and I got to chat with some cool people like Archmage/Andromeda (who showed me stome stuff he was working on for the ASD-demo that won ASM07 this weekend), Zzap69 (a former Noice-member I never met before), Fix/TRSI (a fellow DTV owner who was kind enough to let us use his machine in the compo when mine didn't cooperate with the bigscreen projector) and many others. Best of all, I won the mixed demo competition with my DTV-demo, Uncharted Territory!

Mad crunchtime!

2007-07-27T00:36:00.000+02:00

I've been in completely insane coding crunch mode for almost two weeks now trying to finish my new DTV demo in time for Big Floppy People 2007

The amount of boring work that goes into linking everything together, making sure that parts cooperate nicely etc. is mind-boggling to say the least. I think I've spent about as many hours now just with putting the parts together as I have actually coding the ffects.

Well, now I'm ALMOST there, still some minor bugs, but I'm so damn tired of this that I think I will consider it ready now! :)
Anyway, here's a sneak preview of the intropicture from the demo:

Release should be now on saturday if everything works out!

The C64DTV - a new "oldschool" demoscene platform?

2007-05-07T14:23:00.000+02:00

The C64DTV and Hummer are cheap connect-to-TV-and-play toys. The cool thing is that the hardware implements a good approximation of the classic C64 and also extends it with new features like 256-color mode, 2Mb RAM and a blitter.
For democoders wanting to continue with oldschool productions but looking for new challenges, it is an interesting choice.
I have a background in C64 coding (haven't released anything since early nineties though) and I am excited by it!
Yesterday I released my first little DTV-demo "Hello DTV World".

The demo is very basic, the only DTV-specific things exploited is the 8bpp mode for the intro pic and the 256-color character mode used for the plasma,
but I still got a feel for the platform and what the possibilites are.
Compared to the C64 scene which is very mature and almost all technical tricks have been discovered, the DTV is still uncharted territory (however C64 legend Crossbow/Crest have been doing some DTV stuff, so perhaps he will shock the scene and release a demo exploiting every DTV-trick possible soon... :))

Anyway, I think that sceners that are looking for a new platform should give the DTV a thought.

Pros:
+ New platform (but with oldschool flavor!) with lots of technical tricks to be discovered.
+ Familiar coding environment for those with C64 experience.
+ Good development tools available.
+ Cheap.

Cons:
- Needs hardware modding.
- Production of new units has (to my knowledge) halted.
- Still depends on C64 peripherals (C64 diskdrivers are rather slow and low capacity, aswell as hard to aquire nowadays)
- No established scene yet.
- Uncompatible hardware versions (v1 NTSC lacks almost all the new features, v2 PAL has some blitter bug)

More 4k madness!

2007-01-11T22:01:00.000+01:00

Yet another world first (I think) - music and 3D in a 4kb J2ME demo!

Check out 4th Dimension

What you can do with 4096 bytes

2006-11-06T00:21:00.000+01:00

Today I finished a little project I started yesterday - Proof of Concept 4k, a J2ME demo in 4kb (4096 bytes). Runs on all cellphones that supports MIDP2.0 and CLDC1.1.

I've also had to move my homepage, and quite a few files went missing in the move, I'll try to recover them as soon as possible.

On a completely unrelated note - I've been playing some Call of Duty 2 HQ matches on Clanbase together with some friends at work. For now we are 0-2, but we are looking to improve! :)

Sneak peek

2006-08-31T22:01:00.000+02:00

Here's a little sneak peek of my latest project. This screenshot if from of an early beta of my new J2ME shoot'em'up game:

Sweden vs. Finland

2006-08-14T22:39:00.000+02:00

Tonight I saw the Swedish national basketball team versus the Finns.
Sweden played rather poorly for large stretches of the game but in the third quarter they really turned it up and erased a large deficit to take the lead, but in the fourth quarter the Finns regained the initiative and won the game. Most impressive was probably former NBA player Hanno Möttölä who displayed some great moves in the post.
Anyway, I had a great time, eventhough somewhat downput by getting confirmation on the fact that "real" basketball players are SO much faster, bigger and better than myself! :)

Long time, no update

2006-08-14T22:31:00.000+02:00

My poor blog has been subject to neglect for quite some time now, so I better change that.

I just had four weeks of great vacation, and besides going to the beach, fishing and playing basketball I went on a little roadtrip to Säve with my brother and some friends to check out some great street cars runing the quarter mile.
But ofcourse I still had time to do some hardcore coding. As usual I didn't work on any of the projects I originally had planned to, but instead started something completely different.

The result is World Record, a little demo for the Texas Instruments TI-83 graph calculator, featuring the largest scrolling grayscale picture ever!

Screw McDonalds

2006-04-03T22:56:00.000+02:00

So a couple of days ago I picked up some McD's food on the way home from work.
When I had almost finished my salad, I saw something glimmering at the bottom of the bowl:

What kind of treause could this be? A prize?
After some further searching, this was what I found:

Two bolts. Somehow I doubt that two well-worn screws are part of the normal makeup of a side salad!
But maybe I'm overreacting, perhaps it is some new kind of marketing ploy, where you get the pieces one by one and have to assemble it later. I wonder what could be hiding the next time I eat a Big Mac, a couple of tires perhaps?

If only I had lived in the US, then I could have claimed that I bit into one, hurt my teeth and then sued McDonalds for about five gazillion dollars...

CeBIT 2006

2006-03-12T14:06:00.000+01:00

My employer was kind enough to invite everyone at the company on a trip to CeBIT.
We started out from Sweden thursday morning and drove down to Hamburg where we stayed overnight. Friday morning it was snowing a lot, and it took us quite a while longer than planned to get to Hannover. Luckily the -1C and snowing that we started out with in Hamburg had turned to +14C when we got to Hannover!

For those of you who don't know this - CeBIT is HUGE, there's no way to cover the entire fair in only one day, but we did our best to atleast see the most interesting stuff.

The first thing we checked out was Toshiba, were I had expected to see SED technology in action, but it was nowhere to be seen. They did show a lot of HD-DVD demos, and while the detail level was great (which even made you see a lot of the imperfections from the filming process, grain etc.) there seemed to be some choppiness with scrolling/panorama shots. I don't know what could case this, perhaps the material was 30 fps upconverted from 24, which sometimes can show such artefacts.

Apart from SED which was missing, there were a LOT of other highdef displays. Plasma, LCD, LCOS etc. After seeing what feels like thousands of screen, the overall impression was that plasma displays delivered the best picture overall. Most impressive of all were the large 100+ inch 1920x1080p screens that many were showing. Gargantuan size and simply awesome picture, even when viewed from close range.

Panasonics 103" monster plasma

Me next to Samsung's 102" plasma

LG's 102" plasma flanked by Christian and Anders

Since one of my hobbies is developing games for cellphones, I also made an effort to see what was new in this area. I saw a couple of phones aimed at gaming (better control layout, 3d acceleration etc.), but they seemed to be for the asia market only so far.

Highres screens (320x240 etc.) also seems to be more common now (which from a developer standpoint means yet another set of art has to be created probably), but atleast Sony-Ericsson still seemed to have quite a few new models with the good old 176x220 screens. I also have to mention the new phones from VK mobile, a company that I never even had heard about before, but they had some very nice looking superthin phones with OLED screens. While they didn't have camera, everything else seemed to indicate a capable phone, but with a weight just a tad above 50 grams!

Samsung game phone

LG game phone (SV360) with 1 Mpoly/sec 3D acceleration

Closeup of the LG phone

Other than that, we saw about fivehundred billion MP3 players and iPod accessories, and a LOT of companies ripping of other companies design and ideas.

Someone is trying to bring the Commodore brand back, selling MP3 players and mediastations I think it was, but atleast they paid homage to the machine that built the brandname!

A real classic makes an apperance at CeBIT

And ofcourse, there were other things besides technology to look at...

Viking Vex released!

2005-12-25T13:51:00.000+01:00

It has been a lot of work, but finally Viking Vex has been released. More screenshots, demo version and information on how to purchase the full version is all available at:
SDW Developments website.

The exploding CD

2005-12-19T17:40:00.000+01:00

Remeber that Mythbusters episode where they tested if CDs could shatter in drives? Well, I don't remember their exact conclusion, but I can now say from personal experience - myth 100% confirmed.

We were installing XP on a box here at work, and suddenly *BAM* a really loud bang. Confused as hell, we look at the computer. Nothing seems out of the ordinary, but the windows install has stopped. We eject the drive and see this:

CD totally shattered! Now this was no cheap CD-R with a off-center sticker or something like that, it was an original pressed WinXP CD. Drive wasn't making any strange noise or anything beforehand. Strange stuff...

Beta testing

2005-11-23T23:25:00.000+01:00

Viking Vex has entered the beta phase, at first a small informal beta at the J2ME.org forums. Who could ever imagine there could be so much issues with different devices? *sigh*
Anyway, as soon as the worst issues are worked out, a "real" beta test will be launched at getjar.com.

The name of the game...

2005-11-03T23:13:00.000+01:00

...is Viking Vex! Yes, finally I have decided on a name for my new J2ME game. John is already working on a splash screen which is looking great so far.
Since I have a three-day weekend now, I'll try to get the first beta version completed.

First screenshot

2005-10-24T17:08:00.000+02:00

Progress on the J2ME-puzzle-game has been good, and with the new graphics in place, it looks really nice. Here's a screenshot of the first level (which ofcourse may be changed in the final game):

Graphics preview

2005-10-17T15:36:00.000+02:00

Well, I finally managed to get hold of a very talented artist to make the graphics for my new J2ME game. Here's a little preview of our viking hero:

Going pro and Podfather porting

2005-09-18T12:06:00.000+02:00

I've mostly been working on a J2ME project that I'm considering trying to go commercial with. I've contacted a talented pixel artist regarding the graphics, so we'll see what comes out of it.

But sometimes you need a break and do something else, so I ported Hooy-Program's "Podfather" (the first ever iPod demo) to the GamePark32!

Screenshot:

Download:
Podfather for GP32

SameGame released and some rocket science

2005-07-18T01:02:00.000+02:00

First of all, SameGame2, my J2ME puzzle game is now released.

Now the rocket science part: This Saturday, me, my brother and a friend where going to head to Säve to watch some of Swedens fastest streetracers duke it out on the strip. The weather turned out to be a bit questionable though, so we decided not to go. Instead, I decided to take up some light rocket science and try to construct a water rocket. The blueprints I found on the internet involved some parts we couldn't find just lying around, but with some imagination and duct tape I managed to construct something resembling a rocket. My brother got the dubious honor of being the launch man, and while he ofcourse got soaked, atleast some of the times the rocket went airborne, and once even to a respectable altitude. Great fun!

Chip8 emulator

2005-06-27T00:38:00.000+02:00

As usual I have a really hard time finishing projects. Things have progressed nicely with the SameGame rewrite, and it's almost release-worthy, but I just can't seem to fix those last little details.

Instead I have been working hard on a new project, a CHIP8 emulator in J2ME which I have dubbed MobiChip8. Working from a couple of different C-sources and some documentation I found online, it was quite easy to get it up and running. It will be MIDP2.0 only though, as I need to use drawRGB() to draw the framebuffer. I tried doing a MIDP1.0 version by using a whole lot of fillRect() but it was too slow even on my Nokia 6630 (which is a very fast phone).

And finally San Antonio won the NBA championship, which was the lesser of two evils I must say.

New J2ME game project + the NBA finals

2005-06-15T22:23:00.000+02:00

I'm currently working on a new J2ME project - an update to "SameGame", a little puzzle game I made some time ago. Currently I'm doing routines to create the graphic blocks scaled to any display size the game might run on. Drawing nice-looking circles (especially very small ones) is not as easy as it sounds, I've been trying lots of approaches, starting with using the built-in fillArc() but currently leaning toward my own special implementation.

The NBA finals is also under way, and saying that Phoenix-Miami would have been a more exciting matchup is an understatement. San Antonio can play some OK basketball, but Detroit's defensive-minded (more like destructive-minded) style of ball isn't my cup of tea. In last nights game they showed Stevie Wonder sitting courtside - I'm guessing that's about the only audience that can appreciate the Pistons...

ProjectLCD released

2005-05-26T23:19:00.000+02:00

ProjectLCD is released! Watch it and mail me your impressions, or leave a comment on pouet.net.

Homepage downtime

2005-05-24T17:52:00.000+02:00

My homepage at Lysator has been down since they've had a serious intrusion in the system. Thanks to Stas from the ArsTechnica message boards, I have now been able to get some webspace, and will soon be putting up atleast a temporary version of the site at sdw.webhop.net

Javascript voodoo

2005-05-12T22:43:00.000+02:00

The transition of my website to the new design was almost complete, when I suddenly decided I wanted to change it to a database-driven site instead, to enhance the possibilites to browse and search my programs.
I soon realized that I didn't know at all what kind of database stuff is available on Lysator where my site is hosted, and that I might run into trouble if I ever wanted to move the site.
So instead I'm now writing the entire site with my own pseudo-database running with client-side Javascript only. Works surprisingly well!

Progress

2005-05-09T12:53:00.000+02:00

I've just been treated to a four-day weekend thanks to some kind of old religious thing that noone cares much about nowadays, but time off work is always a good thing!
Besides giving me some time to catch up on my fast-growing DVD-collection, I made some good progress with ProjectLCD. All parts are in place aswell as some simple transition fades. Now I'll start testing it on some devices (which means I'll start bugging friends and coworkers to install it on their phones!) and a release should not be that far off.
I also did some work on my website redesign, I found a good template by Adam Reeve on www.oswd.org that I did some modifications to. Looks real nice so far.

The sqrt() of all evil...

2005-04-19T17:23:00.000+02:00

I've been working on some 3D stuff for ProjectLCD. It's obvious that I've been pampered by working with OpenGL on PC for a while now, because I seem to have forgotten a whole lot of vector math.
Anyway, J2ME doesn't have any sqrt() function, so I had to research a bit on how to implement it, and boy does it take a lot of instructions to calculate. The performance on slower device will probably take a hit, but it shouldn't be too bad since I only need one sqrt() per triangle.

In other news, I've started thinking about a redesign of my website which is long overdue. I found some nice templates to use as a base, but we'll see when I get around to actually doing something.

ProjectLCD

2005-04-12T22:42:00.000+02:00

Time for a quick update on what I'm currently working on:
At the moment my limited time for hobby coding is devoted to ProjectLCD (Project Lowest Common Denominator), the first J2ME scene demo intended to run on ANY Midp1.0 device, be it a cellphone, PDA etc.
I've got a couple of effects done, and even some nice little "design" backgrounds. Release date is unknown, and knowing my trackrecord when it comes to finishing stuff, it might be a while.

Why?

2005-04-11T13:32:00.000+02:00

So I have created a blog. Why? I don't know. What will I write in it? I have no idea - the future will tell.