Rybags

One of the least used features on the Atari 8-bitters is the POKEY Timers. I've included 2 programs here which give a demonstration of using them. The .ZIP file contains the source code used (just ENTER # it in MAC65 from a H: device), and two BASIC programs which poke in the routines and allow you to alter the timer values with OPTION and SELECT. The BASIC programs should also be loaded from a mounted H: device. Timer_demos.zip Timer2_1.BAS demonstrates using a timer to generate a "raster" interrupt, like on the C-64 or Atari ST. A VBlank Immediate routine starts the timer at the top of the display, and the timer routine changes the background colours to show you where it's being initiated. Such a technique would be useful in situations where an interrupt is needed on an exact scanline. Timer2_2.BAS demonstrates using a timer routine which then uses forced volume level to output a sawtooth waveform. The program POKEs in a 16-byte waveform, which you can alter if you want to. Note that POKEY timers aren't emulated entirely well, as Atari800Win+ will only generate the IRQ at the start of a scanline. The programs will work much better on a real machine. Also, since the Atari has so many different IRQ types, the POKEY timers are fairly low on the priority list as far as the OS IRQ handler is concerned. As such, the programs steal the Immediate IRQ vector, and give top priority to POKEY Timer #2. Feel free to toy around with the programs, you can also change the precision of the timing by using different values in AUDC ($D20F, 53269). The assembly routines can be found using the monitor (F8), and start at $4000. Also note: if you feel like doing a serious project using timers, that there are timing differences between PAL/NTSC. A program which uses timers to do graphics changes on one system will probably not function properly on the other. For doing sound though, the difference would be entirely tolerable (as the case is for normal audio anyway).

Not true. 1016783[/snapback] It's a lot easier, even if you just use Notepad and import the files e.g. ENTER #H6:TESTPROG.SRC,A. The shittiest thing about Atari800Win is that it makes the keyboard act like the one on a real machine, except worse.

Mine are also "wonky" but nowhere near that picture. Maybe you could glue in some plastic strips on each side (vertically) to help keep the keys straight.

http://cgi.ebay.com.au/ATARI-2600-DARTH-VA...1QQcmdZViewItem Not interested myself, but I just spotted this on Australian eBay. The box indicates that it's a 2-switch clone, but the description mentions a "Darth Vader" style clone. Possibly of interest to collectors, and it has 64 games built in. No-one's bidded on it yet, under 2 days remaining and the price is sitting on $14. Note that AU$14 equates to little over US$10, and about 7.50 Euro. Edit: Just found another clone, this time a Gemini, with completely different case: http://cgi.ebay.com.au/Gemini-Video-Game-S...1QQcmdZViewItem

I'm fairly sure you can buy (or maybe build) adaptors to allow a PS2 type mouse to be used on an ST or Amiga.

The ST floppy filing system is virtually the same as the old FAT12 used back in the early DOS days. The only problem with ST floppies is that the format is just different enough to make reading the disks from many PCs a problem. The best way to transfer 720K disks is to either format them on a PC first (preferably a low-density drive, but they are kinda rare now), or to use a utility on the ST which makes 100% PC compatible disks.

Different regions use different frequency seperation for video and audio for analog VHF and UHF transmissions. For example, PAL in Australia is different to PAL in the UK. For a device using an A/V or S-Video cable, it isn't a problem. But for old hardware using an RF modulator, it can be a problem. I would suggest try tuning the TV. If you can get audio but no or bad video, then I would suggest that is the case. Best bet might be to do a 3.5mm audio output mod, or go the whole hog and do an A/V mod. If the POKEY chip was stuffed, it would be a fair bet that the controller buttons would not function anyway (which would render the console kinda useless).

Bad idea. The C-64 PSU has the same plug as the XL/XE PSU but the pin assignments are different, plus it also supplies 12V AC and 5V DC where the Atari one only supplies 5V DC.

It could be that the printer port has to be configured a certain way in the BIOS (ie - standard, ECP, EPP, etc.). Other than that, I don't really know as I use an APE interface. Maybe check all the lines with a multimeter to make sure the cable is OK.

There was a "feature" in early versions of PacMan where you could stop in a certain part of the maze and never get eaten. In Gladiator, if you attacked one of the female enemies in the right order, you could get to see her topless just before she died. In Space Invaders, it's impossible to get shot by an enemy on the lowest level (before landing), but that would have been a deliberate feature.

Once it was established that the ST was to have a minimum config of 512K and have most of the OS in ROM, the cartridge became mostly redundant. Plus the fact that there is no write line going out makes it only partially useful.

Sounds right. What's the amps rating though? My 1050 PSU is 240V in, 8.5 Volts AC out at 4.5 amps. The cassette recorder also uses 9 V AC, but only at around 1.2 Amps.

The main difference is PAL vs NTSC. Colour 4 on PAL has much less of a red tint and Colour 15 on PAL is the same as Colour 15 on PAL. There are slight differences in the overall palette on different machines, the 130XE tends to look slightly washed out compared to older models. There can also be differences between the same machine depending on if it has had a video mod "fix" applied to it, and which type of video output is in use (e.g. TV, composite, S-Video). Here is a thread where myself and some others have posted screen captures from different Atari 8-bit models: http://www.atariage.com/forums/index.php?s...=78402&hl=video

What is this 256 scanlines described in the text? And switching between 50/60 Hz? The ST can do it, but I've never heard of an 8-bit Atari being able to do it. The 8-bit can only do 240 scanlines and even then, the last line has to be something other then GR.0 or 8 else the display goes crazy.

There's every chance that you would need to run it under DOS, or possibly Win98. WinXP has problems with many old games, even ones which ran fine on 98. In any case, the Atari 800 version is by far the best. You would be much better off playing it on an emulator.

I've got the real 800XL owners manual, but I can't scan it ATM. I've got a PDF of the 65XE manual but it's almost 7 meg. In any case, the manuals are pretty basic and the example programs in them are fairly lame.

It's great that most Atari emulators have a "turbo" setting, but it would be nice to also have a "keep chipset timings" setting like WinUAE. That way, you can speed up the virtual CPU, but things like POKEY timings and ANTIC VBI/DLIs could remain the same. Games would still be playable but much less slowdown would occur. The only thing is that it would be possible to develop games which wouldn't work properly on real machines.

Slow-downs in Star Raiders are due to lack of CPU cycles. To see evidence, try switching to LR scan or the map during hyperspace or when there's lots of screen action.

I've found various old computers to be fine on all the capture cards I've used. The only issue being interference, which is almost always been PC generated. Most drivers have dialogs anyway, which allow adjustment of brightness, hue, etc.

The price of ROMs and RAM would have been an influence too. Back in those days, 8K of RAM would have taken up almost half the space on a computers motherboard. 2K and 4K games were fairly normal, they probably had no idea that superbanked 16/32K games would ever be needed. Even arcade games of the era were lucky to use 16K.

I'm no expert here, but I would guess probably tri-stated. The C-64 allows the VIC-2 chip exclusive use of the bus in Phase2 cycles (which it uses for transparent DMA accesses), although that is the 6510 which is a later variant of the 650x.

Doesn't the drive run slightly faster than normal in "unhappy" mode? If that is the case, then a simple timer routine would be able to detect a modded drive.

Yes. At least in "Happy" mode. I think the unhappy not working is a rarity though. And there were also programs which a Happy drive couldn't copy as well, but probably not until the mid 1980s.

http://www.emulators.com/explorer.htm Gemulator explorer can be used to copy ST files from disk images to another drive. Since many games have been put onto menu disks with the protection removed, it will work fine.

Which disk is it on? My collection is incomplete. In any case, you'd be much better off playing the Amiga version. I just started up my ST emulator for the first time in yonks. I'd forgotten what crap sound the ST has.