Matches in DBpedia 2015-10 for { <http://dbpedia.org/resource/ZX_Spectrum_Contended_Memory> ?p ?o }
Showing triples 1 to 23 of
23
with 100 triples per page.
- ZX_Spectrum_Contended_Memory abstract "Some of the ZX Spectrum's 64 KB addressable memory space is referred to as contended memory. With the rest of the memory, the Z80 microprocessor is the exclusive bus master, so its reads and writes operate at its full bus speed. Contended memory space, on the other hand, is shared between the ULA and the Z80 and the ULA has higher priority. Contended memory occupies addresses 0x4000..0x7FFF of the Z80 memory map. This is the first 16 KB of RAM in the 48 KB machine but the entire RAM of the 16 KB machine.Contention occurs as a result of the ULA reading the display and attributes data in this RAM to produce the TV video display. Contention does therefore not occur during horizontal flyback, vertical flyback or during the screen border.Accesses to I/O are also contended if the ULA must read contended memory while the Z80 must access a ULA I/O port. ULA I/O ports are those with an even address (address bit 0 is a 0).The Z80 must wait whenever the ULA needs to access contended memory before proceeding with its own contended memory read or write. The effect to the user is that programs making use of contended memory or contended I/O run commensurately slower than those avoiding it altogether.However, the ULA must wait for a Z80 read or write to complete before it can stop the Z80's clock and access the memory. As the ULA has no capacity to prefetch and store data in advance, it relies upon the memory being available to read to produce a clean and true video display. If an existing Z80 access is in progress when the ULA must read video data, the read is missed and the display shows blank white pixels in place of the correct video pixels. On the next frame, they may well be read correctly. The consequences of this often appeared as a flickering of missing pixels on the display, or 'snow' as it was also called. To avoid snow, some programs and games only copied data to the display on interrupt, as the Spectrum maskable interrupt was generated by the display vertical refresh signal. This ensures that as much of the display as possible was updated during the blanking and border time when video data was not used.".
- ZX_Spectrum_Contended_Memory wikiPageExternalLink Contention.
- ZX_Spectrum_Contended_Memory wikiPageExternalLink memContRevision.shtml.
- ZX_Spectrum_Contended_Memory wikiPageExternalLink index.php5?title=Contended_memory.
- ZX_Spectrum_Contended_Memory wikiPageID "42706653".
- ZX_Spectrum_Contended_Memory wikiPageLength "3530".
- ZX_Spectrum_Contended_Memory wikiPageOutDegree "3".
- ZX_Spectrum_Contended_Memory wikiPageRevisionID "682211944".
- ZX_Spectrum_Contended_Memory wikiPageWikiLink Category:ZX_Spectrum.
- ZX_Spectrum_Contended_Memory wikiPageWikiLink ZX_Spectrum.
- ZX_Spectrum_Contended_Memory wikiPageWikiLink Zilog_Z80.
- ZX_Spectrum_Contended_Memory wikiPageWikiLinkText "ZX Spectrum Contended Memory".
- ZX_Spectrum_Contended_Memory hasPhotoCollection ZX_Spectrum_Contended_Memory.
- ZX_Spectrum_Contended_Memory wikiPageUsesTemplate Template:Multiple_issues.
- ZX_Spectrum_Contended_Memory wikiPageUsesTemplate Template:Reflist.
- ZX_Spectrum_Contended_Memory subject Category:ZX_Spectrum.
- ZX_Spectrum_Contended_Memory comment "Some of the ZX Spectrum's 64 KB addressable memory space is referred to as contended memory. With the rest of the memory, the Z80 microprocessor is the exclusive bus master, so its reads and writes operate at its full bus speed. Contended memory space, on the other hand, is shared between the ULA and the Z80 and the ULA has higher priority. Contended memory occupies addresses 0x4000..0x7FFF of the Z80 memory map.".
- ZX_Spectrum_Contended_Memory label "ZX Spectrum Contended Memory".
- ZX_Spectrum_Contended_Memory sameAs m.0123hzm9.
- ZX_Spectrum_Contended_Memory sameAs Q18390623.
- ZX_Spectrum_Contended_Memory sameAs Q18390623.
- ZX_Spectrum_Contended_Memory wasDerivedFrom ZX_Spectrum_Contended_Memory?oldid=682211944.
- ZX_Spectrum_Contended_Memory isPrimaryTopicOf ZX_Spectrum_Contended_Memory.