Search found 82 matches
- 25 Sep 2022 00:29
- Forum: GENERAL DISCUSSIONS
- Topic: Questions about the Memotech MTX that you were too afraid to ask...
- Replies: 42
- Views: 37395
Re: Questions about the Memotech MTX that you were too afraid to ask...
Emulating a 3.5 MHz Spectrum on a 4 Mhz MTX is rather optimistic and the effective Spectrum clock is roughly 2.4 MHz. The Speculator outputs 1/6th of the display every interrupt to the VDP, therefore display refresh is 50/6 = 8.33 Hz. That's definitely sub-standard but it's the best I could do at th...
- 24 Sep 2022 13:14
- Forum: GENERAL DISCUSSIONS
- Topic: Questions about the Memotech MTX that you were too afraid to ask...
- Replies: 42
- Views: 37395
Re: Questions about the Memotech MTX that you were too afraid to ask...
Question: Why hasn't anyone produced a modern copy of Speculator? This community is still thirsty for software and the Spectrum has tons. Dave, I know, has a Speculator and so do others here probably. Tony Brewer, the developer, is part of the community and would maybe provide "spiritual guida...
- 06 May 2022 13:12
- Forum: HARDWARE
- Topic: Z80 CPU simulator: Visual Z80
- Replies: 3
- Views: 2825
Re: Z80 CPU simulator: Visual Z80
Tony, this is amazing stuff. :o Incredible that after all these years, the Z80 still has unknown corners to explore. Thanks for the reply, Steve. Visual Z80 is an almost perfect simulation (not emulation) of the Z80 and the Remix version is the easiest way to examine those corners. Here is an expla...
- 05 May 2022 13:03
- Forum: HARDWARE
- Topic: Z80 CPU simulator: Visual Z80
- Replies: 3
- Views: 2825
Re: Z80 CPU simulator: Visual Z80
New Z80 return to zero discovery yesterday: two combinations of input signals will result in a RET instruction returning to address 0000.
- 02 May 2022 14:00
- Forum: HARDWARE
- Topic: Z80 CPU simulator: Visual Z80
- Replies: 3
- Views: 2825
Z80 CPU simulator: Visual Z80
Visual Z80 (VZ80 for short) is an online transistor-level simulation of the Zilog NMOS Z80 CPU. Recently, Visual Z80 Remix (VZ80R for short) was created that uses the VZ80 simulator with a more user-friendly interface: https://floooh.github.io/visualz80remix/ Improvements include Assembler and Timin...
- 09 May 2021 17:27
- Forum: PROGRAMMING
- Topic: Sprite collision test
- Replies: 4
- Views: 4855
Re: Sprite collision test
Martin, many thanks for your tests. MTX BASIC might be affecting the results. I ought to write a short assembler program for you to try, however there is no urgent need for this info. My expectation is that parts of sprites on active lines but completely off the display to the left or right will set...
- 04 May 2021 22:01
- Forum: PROGRAMMING
- Topic: Sprite collision test
- Replies: 4
- Views: 4855
Re: Sprite collision test
I might not be the only one, but I've not tried anything as I don't really understand the question. Sorry! The aim is to test limits of collision using two sprites with same pattern at same x,y coordinate. Test 1 is extreme left test with one set bit at x = 0-32. Test 2 is extreme right test with o...
- 17 Apr 2021 12:34
- Forum: PROGRAMMING
- Topic: Sprite collision test
- Replies: 4
- Views: 4855
Sprite collision test
I'd like to confirm the range of x coordinates for which the VDP does sprite collision detection. I cannot test this myself in real hardware as my MTX is in the attic. I think the following two extremes will set the sprite collision bit: 1. Use two 8x8 (or 16x16) sprites with same patterns. Pattern ...
- 24 Feb 2021 21:18
- Forum: GENERAL DISCUSSIONS
- Topic: RGB mod for TMS99xx based computers
- Replies: 18
- Views: 12045
Re: RGB mod for TMS99xx based computers
To synchronise a Propeller, how about putting /VDPINT on the system bus by soldering a wire (must be yellow) from VDP pin 16 or CTC pin 23 to A25 on J10? This assumes LK12 is missing. The obvious downside of that is that it would stop the board from being "plug & play", most folks who...
- 24 Feb 2021 15:16
- Forum: GENERAL DISCUSSIONS
- Topic: RGB mod for TMS99xx based computers
- Replies: 18
- Views: 12045
Re: RGB mod for TMS99xx based computers
The issue is the difference between 50Hz and 60Hz. Games use the VDP interrupt to update the VDP only when it is not refreshing the screen. Since the Propeller is running at a different refresh rate, it frequently draws the screen partly through an update, resulting in display artifacts such as spu...