Andrew Beresford's Blog

Well, I can’t quite believe this but the Broadcom 43xx based wireless interface in 12″ Powerbook finally works in Linux thanks to the hard work of the people at the Broadcom 43xx Linux Driver Project. Now I won’t have to swap between OS X and Linux anymore. Whilst OS X is a fine operating system, I still love Linux more.

you can have avatars for your IM client. mines a monkey with a serious case of ‘doh!’

how abt using a program which cycles your image, advertising companies/brands?

Google, you are awesome.

Tell me please, oh lazyweb, does Solaris (any version) on SPARC have a way of doing NFS-Root in the same way that Linux does?

Ok, not so exciting computer things.

I saw my first snow of the winter this morning. It was just a light dusting, but it was quite nice to see. I like wintery weather.

This week I went down to London for Annie and Tom’s house party. It was great to see people… a few I hadn’t seen for a couple of years and it was really nice to catch up. I also have to thank Eleanor for having a me, Steve and Maffa over to stay with hardly any notice (thanks to my poor planning!).

In other news, I’ve been working on a crappy little tool for managing multiple Debian/Ubuntu machines at work and home. It basically allows remote updating and upgrading of any apt-get’able box using only SSH, sudo and apt-get. There is more information available. The script basically has 95% of the functionality I need at the moment, so I’m not likely to do any more heavy development of it, but it does work.

Wow a Holmfirth webcam :

click here

Cripes.

JONNY K

Hi, my name’s Martin and I’m an old-skool-aholic. Here’s something that has been fascinating me recently.

One of the few things I can remember about being 10 in 1990 was the absolute and easily demonstrated superiority of the Amiga for demos and gaming over the PC. I remember the family Amstrad 286 slowly gathering dust (save for the odd game of Wolfenstein 3D) while my poor A500 gradually turned yellow from relentless use by myself and 4 younger siblings.

Recently I’ve developed a yearning for those early days of metal-bashing simple, documented hardware. I’ve been looking into what it would take to write an impressive demo for a typical affordable 1990 PC, say an 8086 with VGA graphics and some sort of audio hardware.

During my initial research I’ve discovered several interesting things about these old PCs in general. First of all, the original 4.77mhz 8088 isn’t as slow as you might think. It achieves 0.22 dhrystone mips, which compares favourably to the Amiga 500, which gets about 0.55 on the same benchmark. Of course, you may argue a 68000 has a better “flat” memory model, and I would agree. The 8086 isn’t totally hobbled by segmentation like a Z80 or 6502, though. A program in one segment can read and write data in another, after all.

An average of 220 thousand instructions per second is actually pretty respectable. There’s certainly plenty of CPU-time per frame to do work, provided you don’t have to push individual pixels do audio mixing. Which is normally where you expect our “old-skool” PC falls down compared to the Amiga. The lack of hardware-offloading. But things are really not as bad as you think.

I’ve been looking at the VGA and I’m surprised at it’s capabilities. On paper it is superior to the Amigas graphics hardware (even the AGA) in many ways. The most common VGA mode for games and demos was 320×200 with 256 colours from a palette of 262144, although 400×300 was possible with a bit of register magic.

All the registers are there to synchronize graphics to the horizontal and vertical sync for raster-effects and smooth graphics. Tear-free double-buffering and pixel-perfect hardware scrolling (both horizontal and vertical!) is possible using exactly the same mechanism as is used on the Amiga.

The VGA has “chunky” graphics, meaning one byte per pixel. It’s what made Wolfenstien 3D and Doom possible, and possibly contributed to the A1200s early demise as a gaming platform. The Amiga has “planar” graphics, which is a whacky method of laying out graphics using 1 bit per pixel frames. Changing the colour of a single pixel is therefore hard work.

The VGA lacks a copper (a piece of hardware that can be programmed to push values into registers on certain scanlines), so the cpu has to poll the beam registers (but that doesn’t take much cpu time to do). Also the VGA has no sprites or blitter, but the chunky mode means that a lot of things you need to use the blitter for on the Amiga are simply not needed with VGA.

I can’t see any real reason why all those early PC demos seemed to look so bad. I guess the Amiga attracted all the good coders away from it!

Now, the sound. A 1990 PC with sound would have either an Adlib card or an original SoundBlaster (which is Adlib compatible). The Adlib is a 2-operator FM synthesizer with 9 voices. Each “operator” is a sine wave generator with an ADSR (attack,decay,sustain,release) amplitude envelope. The operators can be stacked so that one modulates the frequency of the other, which can give square-wave-like and sawtooth-like timbres.

This is actually a powerful synthesizer, and comparable to the Yamaha DX7 (a 6-operator FM synth), which was used by many mid-80s synthpop bands. After listening to some adlib tunes from www.chiptune.com I came to the conclusion that it “rocks”. Your mileage may vary, of course.

I prefer digital sound however, so I’m more interested in the soundblaster. The soundblaster has a single 8-bit DAC with a maximum frequency of 22050hz. Not brilliant, but with care I reckon you can get useful results. First of all, if you assume a 4.77mhz processor, full sample mixing is right out of the window. To play a MOD, each sample would require several adds, shifts and table lookups and the CPU simply doesn’t have the power (at least at a listenable sample-rate).

If you throw away volume and frequency scaling, however, and simply add each channel together, the mixing process is vastly simplified. Playing different volumes and frequencies would require different samples, but this could be implemented using a wavetable of very short chip-like samples. So you basically get the ability to use sampled drums and loops with synth-sounds.

If you assume 220 thousand samples per second throughput on our 8086, it would be possible to mix nearly 10 channels at 22050hz in this way. This theoretical performance may be way too high, but given the 8 bit sample resolution, you probably wouldn’t want to mix more than 4 channels in this way anyway.

Unlike an Amiga, both sound systems are mono, although the Amiga’s hard-panned stereo isn’t exactly ideal.

Well, that’s my current take on the situation. I’m looking forward to discovering what really was and wasn’t possible.

Check out Google Moon!

“In honor of the first manned Moon landing, which took place on July 20, 1969, we’ve added some NASA imagery to the Google Maps interface to help you pay your own visit to our celestial neighbor. Happy lunar surfing.”

…now try zooming right in to see the moon’s surface in maximum detail. It’s true! The moon is really made of cheese!

Playing with a VeiwSonic airpanel cool..

http://www.viewsoniceurope.com/UK/Products/wireless_displays.htm

good for surfing not too good for playing games in my armchair in the house but then that’s not what it’s for.

It has good handwriting recognition or an on screen keyboard like the tablet PCs. and also like tables you can plug a keybaord & mouse in or dock the thing

It is a pure RDP terminal though so no ssh, telnet or anything else for that matter

and sadly it is windows based. However I have just written this entry long hand and found it quite easy with a minimum of editing.