General Home Computer gaming/tech discussion thread

[Baloo]

I think Kool_Kitty, Tomatheious, and Thenewguy deserve the Sega-16 forum award for "Most technical and informative posts". I've never seen people get this depth into hardware on any other video game forum.

[Chilly Willy]

GTIA was nice - you could do 80x192 framebuffer gfx with 16 colors, 16 luminances, or use all 9 color registers for 9 completely different colors (16 colors still, but since there's only 9 registers, they wrapped around after 9, so only 9 UNIQUE colors). Even better was the ANTIC display list coupled with display interrupts allowed you to make very flexible displays with GTIA only where you want it. You could also change the colors on the fly. Pitfall II did that for the player - he's one single-color player with the color changed on a line-to-line basis.

There were some nice demos and a few games that made great use of GTIA modes. The display list coupled with display list interrupts also made it easy for games of demos to do per-line scrolling, for nice parallax displays. The only thing "missing" that would have been fantastic was a second layer. You had one layer + players/missiles. Considering when it was made, that was still pretty good.

[tomaitheous]

GTIA was nice - you could do 80x192 framebuffer gfx with 16 colors, 16 luminances, or use all 9 color registers for 9 completely different colors (16 colors still, but since there's only 9 registers, they wrapped around after 9, so only 9 UNIQUE colors). Even better was the ANTIC display list coupled with display interrupts allowed you to make very flexible displays with GTIA only where you want it. You could also change the colors on the fly. Pitfall II did that for the player - he's one single-color player with the color changed on a line-to-line basis.

There were some nice demos and a few games that made great use of GTIA modes. The display list coupled with display list interrupts also made it easy for games of demos to do per-line scrolling, for nice parallax displays. The only thing "missing" that would have been fantastic was a second layer. You had one layer + players/missiles. Considering when it was made, that was still pretty good.

The A8 pal guys got it lucky though. They take advantage of the two scanline chroma accumulator (one line for luma, one for hue pixles) for PAL. And it looks solid too. On NTSC, looks like crap since it doesn't have that filter. I believe this is the 80x96 color mode.

[Chilly Willy]

The A8 pal guys got it lucky though. They take advantage of the two scanline chroma accumulator (one line for luma, one for hue pixles) for PAL. And it looks solid too. On NTSC, looks like crap since it doesn't have that filter. I believe this is the 80x96 color mode.

Us NTSC folks think you PAL folks are ridiculously finicky about your picture.

80x96 gives pixels that aren't ridiculously stretched, but people did use the one scanline mode (which would be 80x192 if used for the whole screen). Other than 160x192 bitmaps, it's pretty rare to see a full-screen of one mode on the A8 because of the flexibility of display lists. You commonly had a character mode line at the top for game status info, and maybe a couple more at the bottom for a "HUD". The center might be split into two different bitmap or character modes depending on the type of game... or might have GTIA for part of the center where more color was needed as opposed to higher resolution.

One mode I liked for scrolling games was the character mode that gave you four color characters (not three + background, but four colors). That was used by a lot of games. The most common mode, though, had to be 160 by one scanline (160x192 mode) bitmapped.

[Thenewguy]

The problem with bumping this thread is that its missing the beginning (which sets the tone of the discussions) and the end (by which point we'd come to an agreement on some of the things written here)

But still, I guess its still the best option, being that the other threads weren't entirely related

Kitty, the official price of the C64 in the UK in 1983 is definitely £229, starting from some time around the late summer period, I also ran into a news note the other day about a store owner dropping his price to £195 and getting in trouble from Commodore where its mentioned that Commodore don't like the C64 to be lower than a minimum of £199 (basically there's store choice to drop from £229 to £199).

Later on, when the C64 started to really take off in Britain (~1985) I actually ran into another interesting news note, which stated that WH Smith (probably the biggest supplier of mainstream computers in the UK at the time) had dropped the C64 to £150 in response to the release of a newer Commodore machine (can't bloody remember which one it was anymore) they (quite prematurely obviously) decided that the new machine made the C64 a hard sale at its RRP and so dropped the price to a level where they no longer made any profit, which is where it stayed.

EDIT: yup, price drop to £150 early-ish in 1985, news note in Popular Computing Weekly vol 4 no 22 states that in response to retailers suddenly dropping the price Commodore decide to make a package, a C64, joystick, Datasette, and copy of International Soccer cartridge bundled together for £199, they believe this will help stabilise the market.

I know the Spectrum isn't really your area of interest, but I ran into some other stuff about it, this thing here, the "Fuller Box" 3rd party peripheral



Was released in March of 1983, and gave the Spectrum a joystick port, speaker, and an AY-3-8912 sound chip. Unfortunately only a handfull of games supported it, but what I thought was surprising is that it was only ~£10 more expensive than the hugely popular Kempston joystick interface (£29.95 vs £19.50) with the Fuller Box you got a joystick port anyway but as a bonus you get the speaker and AY-3-8912 on top of it for £10 more (although the Kempston price was dropped fairly quickly to £15 later though)

This, and the previous conversations we've had, have really signalled the deathnell for the 128k Spectrum in my eyes, I will argue to the ends of the earth that the Spectrum 48k was a fantastic deal, but as far as I'm concerned now the 128k Spectrum on the other hand was an utter, utter joke. By 1986 Sinclair should've been releasing a proper sizeable upgrade, instead we got 128k memory (by 86' memory prices were ridiculously cheaper anyway) an AY sound chip (available from 3rd party companies for nearly three years by that time, and for £29 with joystick port) and a marginally (though still not very good) improvement to the keyboard, all for £50 more than the 48k had been two and a half years earlier

Other notes -

Not sure if I mentioned it, but I like the look of the XL models now, I ran into a high quality picture of a mint 800XL in Retrogamer magazine and it looked very nice (not as nice as Spectrum though of course ), I still think the older models look awful though, and with them I've actually used them in the flesh before in the past.

Being that this is now the main micro topic I'm re-posting my video for posterity (made in response to that other video Kitty posted that made it look like the Spectrum had nothing but monochrome arcade ports)

[kool kitty89]

The A8 pal guys got it lucky though. They take advantage of the two scanline chroma accumulator (one line for luma, one for hue pixles) for PAL. And it looks solid too. On NTSC, looks like crap since it doesn't have that filter. I believe this is the 80x96 color mode.

Interesting: so PAL interpolates color not just in terms of horizontal line resolution (ie the 4.43 MHz clock), but also in the vertical? (so 2 dimensional chroma subsampling -sort of like an analog counterpart to what H.261 implemented?)
Wouldn't that also apply to all platforms using PAL composite/RF?

So you could use GTIA in PAL composite with 80x192 interpolated to a pseudo 80x96 display with vertically blended colors (sort of like horizontal blending possible with NTSC stuff with integer multiples of the color clock)?
If you got unique values for all combinations (ie green above blue is different from blue above green -as horizontal artifacting often does), that would give 256 colors... but if it was more or less just blending that would only allow ~136 colors as such. (and that's only if using the 16 color fixed common mode rather than the 9 indexed color mode)
And that wouldn't be limited to 96 pixels either, but you could use it more specifically for full res grayscale (luma) and 1/2 res color overlay, or for translucency effects. (using horizontal bars rather than vertical )

Of course PAL can't do 320 wide artifacts like NTSC, but that wasn't hugely used on the A8 either. (it wasn't all that useful unless you also implemented tricks for more than 2 true colors per scanline in that mode -I'm not sure what sort of indexing the character modes allow for that -you'd think they'd have allowed more flexible use of the 5 playfeild registers in 1bpp mode, but I'm not sure -the manic miner homebrew game apparently uses some tricks to manage more color as such -something about using sprites as "color RAM'' but maybe it's PAL specific and related to the 2 line chroma artifacts)



There's also the "interlacing" pseudo colors (flickering between 2 separate palettes/bitmaps/tilemaps) that works much better in NTSC than PAL (due to 60 vs 50 Hz) though that's a bit more limited in use. (namely more RAM, more CPU resource for software rendering -and effectively dealing with 2 2-bpp planes accumulated though flicker)

GTIA was nice - you could do 80x192 framebuffer gfx with 16 colors, 16 luminances, or use all 9 color registers for 9 completely different colors (16 colors still, but since there's only 9 registers, they wrapped around after 9, so only 9 UNIQUE colors). Even better was the ANTIC display list coupled with display interrupts allowed you to make very flexible displays with GTIA only where you want it. You could also change the colors on the fly. Pitfall II did that for the player - he's one single-color player with the color changed on a line-to-line basis.

There were some nice demos and a few games that made great use of GTIA modes. The display list coupled with display list interrupts also made it easy for games of demos to do per-line scrolling, for nice parallax displays. The only thing "missing" that would have been fantastic was a second layer. You had one layer + players/missiles. Considering when it was made, that was still pretty good.

You had some similar effects on other platforms of the time (or older like the VCS) via software timing or interval timers, but not with the hardware driven flexibility of ANTIC+GTIA like that.

Good use of DLIs is one of the critical tings for more impressive A8 games and demos and would have been one of the critical issues for the poor 3rd party development tool support that Newguy brought up. (especially for Europe)

There's a lot more non tech related issues tied to the decline (or lack of popularity) in the US and Europe though, but I think that's been pretty well covered already... if in a round about way and spread through a few different threads. (which I did link to)

[kool kitty89]

Not sure if I mentioned it, but I like the look of the XL models now, I ran into a high quality picture of a mint 800XL in Retrogamer magazine and it looked very nice (not as nice as Spectrum though of course ), I still think the older models look awful though, and with them I've actually used them in the flesh before in the past.

I rather like the prototype Atari 600 (intended 16k+expansion counterpart for the 1200 in 1982 -but canceled).
http://www.atarimuseum.com/computers.../600proto.html
Much like the 600XL but with more black on the case and slightly different styling. (full ridges across the top of the case)

One thing is the color schemes too: the 400 would look totally bad ass in black with that sleek wedge/facet shape. (it's pretty compact too considering what they had to force inside -light enough to reasonably hold in 1 hand and with a similar footprint to the VCS/2600 -narrower but deeper- though a good bit taller)
If they'd been smart about the EU market (and possibly even the lower-end/mid range US market earlier on), the 400 form factor could have been a nice starting point. (for UK/EU obviously cut cost for shielding and some board modifications, shift the market a bit catering to tapes -push the tape drive price as low as possible- BASIC interpreter in ROM along with the OS, and of course aim more than providing good documentation to interested 3rd party developers )

For that matter, the XE line probably would have looked pretty nice in black... or the ST for that matter.
sort of like this but with black keys with white text:
http://starwarslegacy.net/images/ata...xe%20black.jpg



The 1200XL is much like the 800XL but with a bit more bulk (deeper and a little taller) and more angular. Though it's supposed to have one of the best keyboards ever made and is still reasonably compact. (larger footprint than the 400 bit shorter and sleeker)

[Chilly Willy]

Other than a slew of pinball games (Night Mission, Raster Blaster, Midnight Magic, and the Pinball Construction Set), the only games I know which used the hires artifacts for color were Drol and Conan: Hall of Volta. There were probably a few others...