Rybags

Atari realised their mistake using WSync in their keyclick routine. The XL/XE OS instead reads/compares VCOUNT to generate it's delay, making it unobtrusive to DLIs. The GTIA CONSOL register is supposedly an I/O port. There aren't any data direction bits addressable, so it could be assumed that it's hardwired for 3 inputs, 1 output. As for doing sound effects, check out Night Mission Pinball. It's one of very few games which use it. Since POKEY can do forced volume to 16 levels (or more if you add extra voices), it's obviously the way to go since the GTIA only does 2 levels. With some tricky programming, you could probably get some passable sound effects out of GTIA, but you would have very few cycles left over to do much else.

I never thought much of the 8-bit Galaxian but then again I didn't like the arcade version either (although I was a big Galaga player). But, some arcade games, for some reason just were'nt converted well to the home platforms, and those 2 games (with very rare exceptions) are good examples.

The flicker you experience will depend on your refresh rate on the PC monitor, whether the emu is in PAL or NTSC mode, etc. Real hardware will flicker too, TVs generally get less of it than monitors due to higher persistence of the tube. Hint: some video capture cards have a "blend" option (and some do it by default). Blending merges 2 interlaced frames together and as such will eliminate flicker.

Why pack? It's only beneficial if you need to get stuff to fit in a 130K disk. Other than that, it usually takes longer to load/decrunch anyway.

The built in floating point routines do binary to floating point conversion. From there, it's fairly simple to convert from floating point to ASCII.

Upload a short example of an executable so we can have a look.

Shop around, you should be able to score an 800XL or 130XE + disk drive for around that price. And forget games unless they're on cartridge, or good original disk games with box/manual included. Virtually every game ever commercially released is available to download somewhere, and with an APE/SIO2PC interface you will be set.

Just restored my old eMail files, here is an extract from the mail I sent and the reply I received: My email to Clarence: today I performed the 2.0 SuperVideo upgrade on my Australian PAL 800XL. But, my video output is now worse. The colour appears washed out, and overall the display is sharper, but has a darker blue tinge on the right of the default display (composite input to TV). For some reason, plugging into my capture card on the PC, I now only get a B&W display, where before it was colour. I currently use a plug I made up, with composite output from the XL's monitor port. I added the chroma output previously, and it was fine, although I can't test it at the moment, as I removed the S-Video plug from my adaptor and added it internally to my 130XE. I have also noticed with the 800XL that as well as being washed out, colours are darker. For example, setcolor 2,n,0 now generates an almost black background, where before it was a dark version of the selected colour. I performed the 2.0 mod as per your page: http://www.geocities.com/atarimods/supervid2.html with the exception of not adding the composite on/off switch (Step 6). I also removed the capacitor mentioned in Step 2. I've only visually inspected my solder connections, I didn't want to risk frying anything by using the audible tester on my digital multimeter ( + I'm not very experienced with electronics). Any suggestions? Reply extract: Anyway, I am not sure what is going on. Sounds like a lack of frequency response. But then I never moded a PAL set before. I wouldn't think there was any difference, but I don't really know the PAL standard. Do you happen to have a schematic to the PAL version to compare? It is also very possible that the output impedance is now to low and there is not enough color information going to the monitor/capture card. You might try increasing R66 from 75 ohms to 100 ohms and if you do have C56, remove one end to see if that improves things. Other than that, I don't really know. On all the set I modified, the picture always was better going into a monitor (Commodore 1705) and no one has said anything so far. But then, no one had a PAL set that I know of. Something must be different, but for the life of me I don't know without seeing the PAL schematic. Even then I don't know if I could help you with out having the units to work on. ========================================= To anyone doing a video mod, I would advise some caution, plus it is quite probable that what's good for an NTSC machine might not necessarily be the same on a PAL machine.

From memory, I changed a couple of the resistors back to their original values, and put the diode back in (which the mod suggested to remove). I received an email from one of the guys who formulated the mod I did, I'll try and dig it out. (Just had to reinstall Windoze after it totally crapped itself)

Adding the chroma to the 800XL is easy. Doing the whole video mod is a bit more complex. I did the Super Video for my 800XL but wasn't happy with the result, so I backed off some of it (at suggestion of one of the creators of the mod). I did add an S-Vid port to my 130XE though, and despite having no video mod on it, the monitor output is much better than the RF output (which is very second rate, like most XEs).

There is no "MAME DVD". There are groups around who do distros where if you send them some blanks they'll copy stuff for you, but it's not exactly legal since many ROMs are still under copyright. Since you already seem to have ROMs, you only need to download MAME itself. http://www.retrogames.com is the place to go, it has links to MAME and most of the popular emulators around.

Rewriting garbage into the variable name table is an old trick to stop people viewing/altering BASIC programs. Just use a decent editor to give the variables some usable names.

Reopening the screen after altering RAMTOP is to clean up the memory pointers. Otherwise, you're left with screen memory still sitting around $9C00-$9FFF and free RAM from $A000-$BFFF. When there is no cartridge or BASIC, the sequence during warm/coldstart is: check location 9 (boot flags, bit0=1 means disk has booted, bit1=1 means cassette has booted). Jump to cassette and disk initialize routines through locations (2,3) and ($C,$D) if their bootflag bits are 1, return is expected. Jump through DOSVEC ($A,$B) - no return is expected (or possible) - so this will call the DOS menu, or run your program, or just go to Memo Pad or Self-Test.

I suspect that despite the DUP file I patched having the right pointers that the DOS doesn't go by what the file says, but what it "knows" the length of the DUP to be. But, if the source is available, just roll your own mods for it.

Probably best to make an entire new image and write the DOS files to that. To make the change, I replaced a call to $E456 (CIO call) in the DUP.SYS code. Then I just appended code to the end of the DUP which does the colour changes, then altered the start of the file (load end address pointer). The JMP $E456 is at $3D7C, changed to JMP $4332, code to store colours is there. Just hope that the DOS is smart enough to adjust it's memory pointers upwards by the extra length I put into the DUP file.

When you call DOS, MyDOS re-opens the screen, changing the colours back to their defaults. I had a quick look through the code, the easiest way is to do a patch in the DUP.SYS file. I've added some code to the end of the DUP.SYS file, to change the colours you want, go into the monitor (F8). C 4334 nn (nn= hex value for background colour) C 4339 nn (nn= text colour) To make the change permanent, you have to write the DOS files back to a disk. MYDOS45.zip

Yes. just set bit 1 (OR with #2) to disable the BASIC ROM. To make BASIC stay away at the next warmstart (Reset), store any non-zero value in location 1016 ($3F8). But, make sure you have some program for the OS to run (ie, set DOSVEC [$A]) else the Self-Test will be run. To do things cleanly, you should also set RAMTOP and MEMSIZ (decimal 740 and 106) to 192, then re-open the E: device. That will set the other high-memory pointers right as well. But, that only applies if it's a 64K machine.

POKEY does keys and joystick on the 5200. No mention in the first post of whether his joysticks are dead though.

If the POKEY chip was a dud, then the controllers wouldn't work at all. Sounds more like a bad solder joint or broken trace, or possibly an RF modulator problem. Best bet is to do an A/V mod, which might fix the problem, but at the very least will improve the video quality even more.

It seems I misread the text. The Crystite chart describes the deposits as "known" by the computer players, not what is actually there.

The document seems to indicate that doing an assay can help crystite production, where a plot is adjacent to one containing "high" levels. Is this right?

A lot of modern TVs have component video input (which most good DVD players support). SCART is another option, but is mainly in Europe. The quality of connections, in ascending order on TVs is: Coax (RF) Composite (A/V) S-Video Component (Y, Pb, Pr) SCART (using R, G, B lines) Another thing to look for is PAL/NTSC compatibility. Lots of "enthusiasts" use PAL60 (not actually an official standard - it does PAL resolution at NTSC refresh rate).

In most cases, no reason. The main advantage of using timers would be where a change has to be made on an exact scanline, regardless of scrolling, or in a situation where a graphics mode like text mode 2 was being used. But, the best use would be for digitized sound, but there's still the overhead disadvantage.

I should scan and upload the two contracts for the books I wrote in 1984/5 (Games for Your Atari 600XL and Astounding Arcade Games for the Commodore 64). I could write a novel about how the publisher violated every single point of the contract (although that seems to be par for the course in the computer industry).

Just a few other notes: The formula for the frequency of a POKEY timer is different to the audio frequency. Interrupts are generated at twice the frequency, therefore the formula is Freq=BaseClock / (AUDFn+1) (where BaseClock is 1.79 Mhz, 64 KHz or 15 KHz depending on what bits are set in AUDCTL) Since the program changes the IRQ vectors, it's a good idea to RESET the machine before doing anything else (including running the program again). Edit: Finally (I should have put this first) - the POKEY timers are not related to the Countdown timers, which are software timers controlled by the OS Vblank routines.