ClausB

I'm not sure we can make interlacing work, but I have an idea for generating 480p30 (480 progressive scan lines at 30 Hz). Though I don't know which display devices really support that mode.

Cool stuff!

Thanks for the interesting look at an 800D. Is this hardware at all related to the "LINBUG" debugger mentioned in the published Atari OS listing?

04 is the "Read / not Write" signal from the CPU, undelayed (as opposed to "R/-W Late", delayed for DRAM timing, IIRC). 05 is from the address decoder, signalling that the CPU is accessing an address in the range $E000 to $EFFF. 16 is for the 2600 expansion unit's sound output, which goes through the 5200's audio circuit to the TV. There's also a video input for the 2600 expansion unit. 18 is the CPU's 1.79 MHz clock phase 1. A11, combined with Enable E0-EF, decodes the address range $E000 to $E7FF, a block unused on the motherboard. A0 through A7 are the low 8 bits of the address bus, used to address within the $E000 to $E7FF block decoded above. You've got 256 bytes of space to add peripheral I/O or banked RAM or ROM. Why A14 is there is a complete mystery to me! Data line D7 is the high bit and D0 is the low bit. See also my article at http://www.videogames.org/html/5200Stuff/5200.notes.html and my posts in the 5200 threads.

When I wrote that sentence 25 years ago, I envisioned something more like what Bryan said above, not a full-blown dual-port memory with real-time debugger. It was academic, though, and I never built any such thing. It's the kind of suggestion I liked to put at the end of an article, just to get readers' imaginations going. I don't know if anyone built one, but I've heard Atari had some such things in house.

Too bad about the ABBUC contest. I did not look at the other entries, but Bob's accelerator is too cool for last place. There was some lame excuse about the 1200XL being scarce in Europe, even though Bob's 1st post here about the upgrade says it applies to the 800XL as well! So ist das Leben.

You're right! Remember the TR7 TV commercial with all the wedge shapes? At the end the TR7 pulled into a wedge garage. "The shape of things to come." Right? Maybe the 400 designer had one or just liked the ad?

Yes, the BASIC program drew one frame in GR.6 mode, then changed the OS pointer to screen memory (and changed the RAMDisk bank), then drew the next frame in another 2K region, and so on. It also saved all the screens to disk. On playback, the assembly routine changed the display list pointer to screen memory (and the bank on every 8th frame) 15 times per second for animation.

Both are true. You define that hue 15 = hue 14 + 24° = hue 1 - 24° I define that hue 15 = hue 14 + 24.8°/2 = hue 1 - 24.8°/2 In both cases, hue 15 is in the middle between 1 and 14. Not quite right, because hue 15 - hue 14 is the same as hue 14 - hue 13 and as hue 13 - hue 12, etc. Therefore, hue 15 - hue 14 is much more than 24.8°/2.

If hue 15 is exactly in the middle, then the phase angle would be 360°/15 = 24° That is how I used to adjust my Ataris, except for my 400, since I only had a B&W TV back then.

Better than composite is a monitor with S-Video input, but you have to modify your 800XL slightly to use it. Search these forums for instructions. You also need to build or buy an Atari to S-Video cable. The old Commodore monitor used a precursor to S-Video and it looked great with an 800.

Here's a 144K animation I did for the Axlon RAMDisk way back then.

So either ROM socket of the XL series takes a 27256 EPROM? That would mean you can put in any ROM instead of BASIC into the Atari memory $8000...$BFFF area and use OPTION to disable it. NO! The BASIC ROM has 24 pins - not 27256 compatible.

That works because pin 18 has a weak internal pull-up that keeps the -BE (BASIC Enable) signal high, or inactive. But it could pick up electrical noise and cause mysterious crashes. A better solution is to reconnect pin 18 and disconnect the signal at the other end, pin 11 of U23, the PIA. That way, R85 can pull the signal up strongly. You don't need to remove the BASIC ROM - it should never get selected. If you want, you can remove both old BASIC ROMs from your cartridge and put the XL BASIC ROM into either one of the sockets. Then you'll have the newer BASIC in your cart.

Are you sure?

Are you from Florida?

Don't forget the color delay pot. IIRC, it adjusts the spacing between hues. In the color wheel above, you have 360° of hue and the Atari has 15 hue levels. To space them uniformly around the wheel, the hues should be 24° apart. If the spacing is too big, you get repeated hues between the top end and low end. That appears to be the case with the emulators' hues shown above. There are repeated yellows, greens, and even oranges at the bottoms of the images. Was there ever a standard for adjusting those pots?

Not sure which is better, my 174K 800 or the original Quarter-Meg XL.

Hope you had a happy birthday. Was it number 904, Doctor?

Not through the antenna (RF) connection, but maybe through composite or S-video (from a modded 2600)? Don't EDTVs and HTDVs support 480p30 through YPbPr component inputs (for progressive-scan DVD players)? I know that the color encoding is different between NTSC (composite or S-video) and YPbPr (component) but I thought maybe the progressive scan mode might apply to both. I suppose you could feed the modded 2600 composite video to the Y component input and get 480p30, although without color.

Has anyone tried, in a game or demo, to output progressive scan video (480p) from a 2600? It would seem to be easy, just issue VSYNC every 525 scan lines instead of every 262, no?

Here's an explanation of the 256K XL banking method: In 1984 I designed the 256K "Quarter-Meg" XL RAM upgrade published in BYTE for September, 1985. It used 8 banks of 32K each. In 1985, after the 128K XE came out, I redesigned the upgrade for 16 banks of 16K. Later, that design was sold as the "Rambo XL". The XL and XE computers use Port B bits to control memory configuration. Bits 7, 1, and 0 control ROM/RAM switching. In the XE, bit 4 enables extended RAM for the CPU and bit 5 enables it for ANTIC, and bits 3 and 2 select one of four 16K banks. In the upgrade, bit 4 enables banked RAM for the CPU and ANTIC. Banked RAM appears in place of normal RAM at addresses $4000-$7FFF. Bits 6, 5, 3, and 2 select one of sixteen 16K banks. Four of those banks mirror the normal 64K XL RAM, and four others mimic the extended XE RAM, as below. PB Bank RAM -- ---- --- $FF none normal $83 0 mirror of normal $0000-$3FFF (page 0, stack, OS variables, DOS, etc. -- dangerous bank selection) $87 1 mirror of normal $4000-$7FFF (same address as bank area -- useless bank selection) $8B 2 mirror of normal $8000-$BFFF (usually screen RAM -- not very useful bank selection) $8F 3 mirror of normal $C000-$FFFF (RAM under OS ROM -- useful) $A3 4 extended $A7 5 extended $AB 6 extended $AF 7 extended $C3 8 extended $C7 9 extended $CB 10 extended $CF 11 extended $E3 12 XE-compatible extended $E7 13 XE-compatible extended $EB 14 XE-compatible extended $EF 15 XE-compatible extended Now you can see why the RAM utility program does not recognize $87 because it's the same as normal RAM. You can also see why it crashes with $83 because it probably clobbers the OS, DOS, or even itself when it tries to write into that bank.

I get the hint! Although, it was 80° here today. Forecast says Summer will be over next week. But here in Michigan we have another season between Summer and Winter. It's called FLL. That's FIRST Lego League competition season. Go Programmers!

It was in a Mom & Pop shop in East Lansing in 1980. I had been lusting after the Apple II, but when I saw their 800 running Star Raiders I was hooked. I learned about the 800 and 400 from their very knowledgable salesman, but Pop would not let him deal on price. When a chain store had a sale on 400s in December, I grabbed one along with Star Raiders. Happy Christmas! The first salesman, who had become a friend by then, was bummed but he understood. As consolation, I bought a 32K RAMCRAM from him and watched over Pop's shoulder as he installed it. I was ignorant about electronics then but that really piqued my interest. The salesman friend also let me photocopy his photocopy of the Atari Hardware Manual and, later, the OS manual. I learned a lot about "Candy" and we had a blast. Later when my friend quit, Mom & Pop hired me. We sold Ataris, Exidy Sorcerers, and Vector Graphics computers, plus software and magazines. They wouldn't let me deal either, and we ended up closing shop. But, hey, I got paid for playing Star Raiders! It was in that shop where I got my highest rank ever, Star Commander class 2, while patient customers looked on.

Same here. When I first saw Star Raiders on an Atari 800 in the fall of 1980, I knew I had to have one, but not for $1000. That Christmas, Atari had a promo for their cassette- and cart-based Education System. You could get an 8K 400, a 410, the cart, and some tapes for $400 or $500. But I managed to trade the Edu cart and tapes for a Star Raiders cart. Happy Christmas!