D’oh. The floating bus on the +2A/+3 is broken in this build. Build 271021 is fine, so I’m sticking with it.

... plane and buffers on the address, control and data bus lines. ... Interface 2, ZX Printer and a ROM cartridge in ... an Alphacom 32 printer and a µSpeech. So IIRC ... board, Alphacom 32 printer and a µSpeech connected up ... powered from the backplane, and no longer used it ...

... similar business in London and spread out a bit. ... catered for my skills and the sectors I work ... be happy to change and walk / bus into work instead ... pandemic I've grown older and lazier)

... of instant communication, deliveries and the internet, I see ...

... is used the bus is left floating and will pick ... games display "SPECTRUM" and "PLAY" all over the ...
7) Z80 timing differences. The Z80 in a ... RAM contention models are different between the 128/+2 and ... +3/+2A machines. This would only cause timing ...

... “floating” interrupt. [holub]
- 9640: spec128.cpp, specpls3.cpp: Added initial bus contention ... Spectrum drivers: Improved timing for screen and border updates, and simplified calculations. [holub ...

... /> in 40 - 7F? | Low bit | Contention pattern
------------+---------+-------------------
No | Reset ... valid during whole
T2 and Tw cycles)
During _reading_ ... right as Z80 probes data bus during T3 (fourth) state. So ...

... of the 0x7ffd, 0xbffd and 0x3ffd port contention behaviour.

With ... /umbrella.htm[/url] and apply contention if ULA14 = 1 and ULA15 = 0.
timing?
3. What is fusetest ...

... spirits the value on the bus away and forces a 0 off ... sources diverging on the exact timing - can anyone help?

and will autonomously trigger more if ... are triggered by horizontal sync and are enabled or disabled by ...

... don't take account the contention. There are two instruction ... and 736 instead 735 for second one.

All this timing ... is for 48K machines. The different is between 0.15 and ... 0.20 per cent compared with the teorical (without contention ...

... even throws up timing differences between the 128K and the ordinary +2 ... hit all the most awkward contention.[/QUOTE]
I think ... cycles (extended to 16 by contention). But then I should ... to get ahead on the contention cycle. Assuming that writing those ...

... instruction fetch), and it doesn't apply contention to take precedence ... address put on the bus by the CPU interferes ... in the last 4T the bus is idle (0xFF). ... so it leaves the bus idle for the remaining ... once borked up the timing somehow such that it scrolled ...

... , so there are odd and even frames, which means ... processing all lines (odd and even) on every frame ... the ULA snow effect, and maybe prevent us to ... read something from a floating Z80 bus or similar.
... NTSC outputs (in USA, and maybe some other countries) , ...

... about the Speccy's video contention model - and that's the amount ... CPU?

And then there's the contention pattern where the ... 16, so that means the contention pattern covers a run of ... there some odd stop-start timing thing going on between pairs ...

... check all ICs). Poking and peeking suggested that it ... replaced IC17 with a socket and 4164.

and white, or sometimes coloured ... one of the data bus lines. The soldering & ... the way of info floating around on this version? ...

... for its interrupt routine address and this would conflict with ... z80 reads whatever is floating on the bus at the time, ...
Recall that mixing even and odd peripheral ids means that ... bus and this fools the ula into thinking there is a memory contention ...

... instruction timings
- Added bus contention for IN and OUT
- Replaced the ... memory contention emulation using a more ... />
With all of this timing has improved a lot (Aquaplane ...

... instruction timings
- Added bus contention for IN and OUT
- Replaced the ... />
With all of this timing has improved a lot (Aquaplane ... />
Excellent news. However, memory contention isn't all that important ...

... /> [I]"I think contention occurs whenever the address bus contains 0x4000 - ox7fff ... for a Address Bus = 0x4000 - 0x7fff AND MREQ high contention selection?

timing isn't too sensitive.

... of mantissa and exponent bits each micro uses to represent floating point ... own floating point library by default (not the spectrum ROM) and its ... may also suffer from some bus contention caused by video refresh that ...

... contention to IO instructions, which made their read or write data bus ... the more conservative memory contention model instead of the ... />
To maintain timing compatibility, the later ULA versions ... of the intended IO contention model, and so the "cockroach" ...

... I/O request to itself, and after contention (if necessary), it sends ... separated inputs, form the address bus contents.

Then, the ... an excesive number of floating wires crossing here and there, right?

... B]14335[/B]. The instruction timing table indicates this instruction behavior ... [*] [B]4[/B]: After the bus is finally available (at cycle ... by contention. Since we are now at cycle 14345 and, according ... [*] [B]3[/B]: After the bus is finally available again (at ...

... happening between pixels and attribute fetch goes unnoticed and ULA always fetches ... may be due to subtle timing differences, or because the +3 ... the screen address on the bus. But in either case the ... not really needed for the contention, it is perhaps just an ...

... outputs derived from floating inputs onto the address bus.[/QUOTE]:o:confused ... is to alter the addressing/contention of the ULA. Now depending ... are lifted from the PCB and then wires are soldered to ... fit into the socket normally and make sure that the wires ...

... + is another clone without memory contention.

Given the ... point to RAM) and display issues (128K timing but a ridiculously ... the lack of memory contention was probably about the ... with some fairly clever bus buffering/arbitration logic. Apparently ...

... long trying to juggle the contention or communication between the processors ... job (such as sound) and give it its own memory ... and program code, and just communicate with it over a simple bus ... had co-processors to do floating-point maths, which could work ...

... edges of the clocks for timing, while the Z80 divides the ... .

But the memory bus arrangement of the 6502 means ... memory mapped display without memory contention.

It was easier ... /> This list could go on and on and on, but I think ...