Search found 2737 matches

by Chilly Willy
Thu Jun 13, 2019 6:24 pm
Forum: Megadrive/Genesis
Topic: Designing a cooperative-threaded scheduler for an emulator
Replies: 9
Views: 265

Re: Designing a cooperative-threaded scheduler for an emulator

The problem with single-threaded emulators is that single thread performance has stagnated over the last decade or so. Other than tiny improvements in IPC efficiency, virtually all work have been towards adding more and more threads in parallel. We've seen a huge shift in game programming in the sam...
by Chilly Willy
Fri Jun 07, 2019 9:17 pm
Forum: Demos
Topic: Devwill Too MD
Replies: 4
Views: 1827

Re: Devwill Too MD

Looking pretty good. I love the music.
by Chilly Willy
Wed Jun 05, 2019 2:57 pm
Forum: SGDK
Topic: Assembly inline C - example
Replies: 6
Views: 298

Re: Assembly inline C - example

If you want an example of 68K inline assembly, here's a routine I did in a SCD demo. static fixed_t FIX_MUL( fixed_t a, fixed_t b ) { fixed_t res = 0, c = 0, d = 0, e = 0; asm volatile ( "tst.l %1\n\t" "spl %5\n\t" "bpl.b 1f\n\t" "neg.l %1\n" "1:\n\t" "tst.l %2\n\t" "bpl.b 2f\n\t" "not.b %5\n\t" "ne...
by Chilly Willy
Fri May 24, 2019 11:39 pm
Forum: Demos
Topic: Goof Troop UNNOFICIAL v0.16 (Demo) - SGDK - Sega Genesis / Mega Drive
Replies: 4
Views: 607

Re: Goof Troop UNNOFICIAL v0.16 (Demo) - SGDK - Sega Genesis / Mega Drive

Coming along well. Your link for the file got cut off. The one in the youtube video is fine.
by Chilly Willy
Fri May 24, 2019 3:00 pm
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 112
Views: 5305

Re: Questions on writing a new Mega CD emulator

I think the primary benefit of an open BIOS for the CD would be to help facilitate CD replacements. The CD drives on these systems are now so old that they're not very good, even when "new". The replacement I got for my CDX is barely any better than the old drive. An open BIOS would allow replacing ...
by Chilly Willy
Tue May 21, 2019 10:12 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

Yeah, that's just silly. I can understand not handling SMS pass-thru, but not passing through /DTACK? There's a number of things I wish they had done on the 32X, like supporting 16MB flat addressed carts. The cart port has all the address lines, and the 32X maps the cart into a 32MB space. They coul...
by Chilly Willy
Sat May 18, 2019 2:31 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 40
Views: 4733

Re: Cart Design Questions

You should only drive /DTACK when the address is for your device. It should be tristated any other time. The MD drives the /DTACK line for other devices when the 68000 addresses them, like the VDP and work ram.
by Chilly Willy
Fri May 17, 2019 11:17 pm
Forum: SGDK
Topic: Sega Genesis Dev Kit (SGDK)
Replies: 789
Views: 343118

Re: Sega Genesis Dev Kit (SGDK)

4KB is pretty low. If I had had code like that, I might have been able to work it into the Neo Myth menu, regardless of the speed issue. At the time, the code needed 32KB (or was it 64KB?), and had to be accessible as bytes. It was too big for what work ram I had, and I couldn't put it in the Neo My...
by Chilly Willy
Fri May 17, 2019 3:23 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 40
Views: 4733

Re: Cart Design Questions

Note that a number of FPGAs have MCUs built into them. ARM+FPGA is actually pretty common.

An active low open drain /DTACK should work on the MD, but remember that /DTACK goes low when the memory is ready, not when it's waiting.
by Chilly Willy
Thu May 16, 2019 2:23 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

TmEE co.(TM) wrote:
Wed May 15, 2019 9:56 pm
VDP is what generates the !DTACK *for* 68K. During DMA the 68K is in bus requested state so that signal has no meaning of any sort.
Indeed. Think of it like the 68000's wait control rather than a vital bus control signal independent of the 68000.
by Chilly Willy
Wed May 15, 2019 2:39 pm
Forum: SGDK
Topic: Sega Genesis Dev Kit (SGDK)
Replies: 789
Views: 343118

Re: Sega Genesis Dev Kit (SGDK)

Take it from me - zlib is worthless on the MD. I tried to use it with the NeoMyth menu as many rom images are compressed, but it's ultra slow and uses way too much ram to decompress.

As to java... could be worse. He could be using C#. :x :lol:
by Chilly Willy
Fri May 10, 2019 8:14 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

Yeah, what I said was a bit ambiguous, so I don't blame you for the confusion. That web page on 65xx timing was awesome! Bookmarked. :D As demonstrated on that page, read/write cycles take one cycle, but the 6502 isn't a single cycle processor, which is why I said that despite taking one cycle to re...
by Chilly Willy
Fri May 10, 2019 2:27 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

You have to remember that the 68000 takes multiple clock cycles to access memory (generally 4 clocks), while 65xx variants take 1 cycle. However, the 65xx cannot transfer memory on every clock, so that's moot. Also remember that the SNES uses a BYTE bus for data while the MD uses a WORD bus, so the ...
by Chilly Willy
Fri May 10, 2019 2:24 pm
Forum: Blabla
Topic: Strong Buzz for new Amstrad CPC game
Replies: 11
Views: 688

Re: Strong Buzz for new Amstrad CPC game

A quick check of the CPC cart pinout doesn't reveal anything like DMA support from carts. So doing animation that size that smoothly is still a real accomplishment. The game (what little they show) looks really good.
by Chilly Willy
Thu May 09, 2019 7:33 pm
Forum: Blabla
Topic: Strong Buzz for new Amstrad CPC game
Replies: 11
Views: 688

Re: Strong Buzz for new Amstrad CPC game

Sik wrote:
Thu May 09, 2019 5:48 pm
Isn't that just a prerendered animation?
Yeah, clearly. You aren't going to do a real 3D rotating car like that on an 8-bit system... well, not at that speed. My guess is it's a HUGE cart - which is fine. Quite a few older systems could have really nice games these days with a good size cart. 8)