Contention - redcode/ZXSpectrum GitHub Wiki

Author: Woodmass, Mark

Release date	Links	Download
2005-03-11	Forum post	tzx (original URL)
2005-03-03 (unreleased, provided by the author)	Discord post	tap (hosted) - zip (Discord post)

The output shows a range of t-states (cycles) since last interrupt and for each of these t-states gives information whether contention by ula takes place or not.

NOTE: The programme is set to timings of 128K Spectrum (70908 t-states in a frame), so as is, it is 128K only test. The test can be easily adapted to work on 48k machine though.
To make this a useful test for 48K machine, do the following:

1. Load the tape in 48k Spectrum. When the tape is loaded and the execution starts, break into basic (pressing Caps shift + Break will do)
2. Change line 20 from 20 LET cycles=70908 to 20 LET cycles=69888
3. It is also good to change line 30 from 30 LET start=14350 to 30 LET start=14325 so you can observe the moment when contention starts, which is t-state 14335 (assuming early timings)
   
4. RUN and see

128K Spectrum:

48K Spectrum (changed programme, as described above):

48K Spectrum (unchanged programme, not useful results):