Crazyace

The Megadrive would be easier to replicate because it's only 2 BGs - the SNES has more complexity in the combinations of BGs0-3. Funny - I always seemed to see more flicker on the SNES when I tested sprites per line - it does support more sprites though.. By timeouts I mean slowdown ... As there are no h/w sprites there would be no flickering at all. On both the Megadrive and SNES there was a real limitation on how much data you could transfer to the VDP in a frame. I thought a bit more about Mode7 - the quickest DDA texturer I can think of in ARM code would be 5 instructions/pixel , which would need a 21MHz ARM to run at 60Hz (320x224x8bit) so a 12MHz ARM would have to cheat a bit

I think a 12MHz ARM2 ( In some articles the ARM3 wasn't that much faster clock for clock than the ARM2, even with the cache ) would match a 33MHz 386DX PC at Doom. Also the screen could be set to 160 pixel mode 256 colour - so the 'windowed' PC version would be full screen ( like the jaguar version ) - and double buffering rather than copying to VGA memory would also be a big saving. This is a 1990 comparision - the 3D0 was 93 onwards... I'm really thinking of this as a comparision to SNES / Genesis , with the added 3D capabilities ARM3 would be nice - It might even be possible to cost reduce earlier if it's a console rather than a low volume computer range. Yes - 1MB of DRAM would actually compared well to the cost of all of the different rams found in the SNES or Genesis. I think I'll have a look to see if there are any youtubes of doom style games running on old ARMs.

I expect it would be able to match the Megadrive pretty well for 2D - it would be a different system, no sprite flickering , more timeouts if the screen had too much happening ( like the Amiga or ST or PC ) Handling the 4 layers plus sprites of the SNES would be more difficult - but to balance that things could be done that would require the SuperFX chip on the SNES. I'd think of it like a faster A1200 or Falcon, a 12MHz Arm2 ( or Arm3 ) should be nearly twice as fast as the 68020/68030 found on those systems. It should also vastly outperform the 386PC's due to the local memory graphics ( one of the bigger limitations of VGA ) Cache/No cache is interesting - at this stage and clock the memory speed was still keeping up with the CPU speed. I'll have to think about Mode7 at 60Hz - something similar could be done ... after all the Falcon managed a mode 7 effect ( ) Also in terms of sprites you could make a much more accurate streetfighter or mortal kombat as there would be no 256 pixel limit on sprites in a line. Yup - software scaling on sprites would be a big win in moving a lot of the Sega style driving games.. ( PowerDrift or Outrun ) No matter how fast the custom cartridge is - the limit would be the transfer to the VDP. With this machine - as video comes from ram you could have a card with a 3D accelerator in and just point VIDC to the cartridge memory Probably 224 lines would make sense, for NTSC TV's For 1990 I would think a cartridge - the aim would be to compete with the Genesis , SNES , PC Engine and NeoGeo. There are disadvantages to this Arm system - but the interesting thing is that it was a real product - and for a console it would cost a lot less than it did in a computer

Doom didn't come out till 1993 - but I was able to run it on a 386 in a stupidly tiny window

Sounds intimidating. Btw what is a VIDC? It's the Video chip that Acorn designed to go with the ARM in the Archimedes. Shares main memory, and has 1 / 2 / 4 and 8 bit per pixel chunky modes - making it easier to use than the Amiga/ST bitplanes, and much quicker than the VGA memory on PC's ( at least till VESA local bus cards arrived in 92 ) It also supported 8 channels of DMA sound - each with stereo panning. It only had a single sprite though

I'd be tempted to look at a console version of the Acorn Archimedes.. An [email protected] + VIDC would give you a machine with 160/320/640 x 256 x 256 colours from 4096 , with a CPU powerfull enough to match the SNES/Megadrive graphics in software, as well as matching any 1990 PC at 3D.

That's a really nice utility... and you mention you've patched the encryption program for use with Skunk as well .... cool.

I'd be happy with a bare board that supports both

If you ever make a newer 7800 harmony - my number one request would be to make it 'double ended' - so it could also work in a 2600 ( I'll order a 2600 version today anyway - it's got to be better than burning eproms )

I'd forgotten the suckiness of the PAL colours... I guess I need to find a NTSC 7800 somehow

The first 2 images look pretty green on my 7800 (pal) - is the slideshow designed for PAL or NTSC?

It's truncated - so the answer is correct ..96*2/256 is 0. You need 16 bit tables for full accuracy - probably 9 bit to handle this rounding correctly

I'm looking forward to further infomation from Curt - My guess is something like 2xTIA in terms of players with Antic supplying playfield. That would give you 4 players ( each with 3 copies ) but still have the hmove hassle to complicate the lives of programmers. Another option ( much cooler ) would be that FRANTIC + STIA are actually improvements over ANTIC+GTIA .. that would be cool - Maybe memory clocks from FRANTIC at 3.58MHz - higher res graphics and players coupled with a slower CPU?

Do you have any other info on the STIA? My guess is that it's compatible with the TIA in some way - it has audio output .. I also noticed that the 6502 is clocked by a /3 from chroma - which matches the 2600 rather than the 800 with a 1.19MHz clock

I saw something similar in the Midsummer pdf for Jaguar 2 ( TEST1 register at f00056 ) - Bits 0 to 4 match your description.

That sounds really cool Gorf - It would be great if it were a 'dev' cart ( like the skunkboard, or the harmony ) with a USB link to a PC.

This is really interesting - what's different between STIA and CTIA? I look forward to reading more on the AHS soon.

No problem - at least you seem to understand there's more than 256 - that's a start. The Jaguar doom has almost a 24 bit feel, as you have 256 shades of each colour - that's why it looks so good.

The lighting on the jag is nicer - CRY works wonders for the DOOM monochromatic lighting. But you're an idiot if you only see 256 colours on the PSX Nothing really blows away the jaguar version though - most people wont pick up on the higher resolution and frame rate.

If just averaging looks a bit crap you could build a 64k table containing the best colour match for any 2 CR values.

If Gorfian reality was a 266MHz PC in 1992 , I think I need to disagree Anyway , disagreeing with you about being able to run voxels on PC/PSX doesn't stop us agreeing that PZ is an amazing game for the Jaguar , or that Jaguar Doom was one of the best versions available on console.

There are things where we disagree , but I don't take issue with everything you say Gorf. Poor ol' Gorfy - it's not 'one upping' , just disagreeing - I think I do it more with Atariksi than you though

PSX display is only 16 bit or 24 bit. It's a lot simpler than the Saturn ( which does have the 256 colour limit in hires going from VDP1 to VDP2 ) so if you wanted to reproduce an 8 bit display you would have to treat the 8 bit data as a texture.

You're correct - for some reason I was thinking of it as a voxel landscape..

Michael Abrash had lots of PC specific stuff in his magazine articles ( and book based on them ) - and I remember a whole slew of game programming books ( not sure how good any of them were though ) Most 3D stuff was in textbooks though..