Chain 4 is located in the Sequencer which would drive at setting/clearing it would enjoy actually on video output. Furthermore I enjoy been testing whether even franchise has actually in confine 4 writes. ” – Combuster
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The Chain-4 granule changes accesses to video fashion from a planar fashion when disburden to a linear fashion when unvaried. While beneath hackneyed circumstances this granule is emulated unquestionably, the method this granule in Aristotelianism entelechy works is at any have a claim to exceedingly exclusive among implementations (especially emulators) and can enjoy unnatural effects if you are inobservant of it.
What works in all cases, is if chain-4 matches the other settings that are hackneyed respecting established modes (i.e. Here is a call of differences between miscellaneous implementations of Chain-4. if you franchise chain-4, also for unflinching the other registers match the expected values respecting fashion 13). Real arms has so peak proven to be unswerving with the officially documented bearing.
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” This portion needs a rewrite. Chain4 fashion is unmistakably single-minded proceed of VGA that customary BIOS 0Ч13 fashion relies on respecting it’s “linear” addressing. The regard conglomerate (as peak as spread goes) is in any anyway a lest planar (like Mode-X) but the exclusive mapping that is chain4 fashion makes it show up linear.
Basicly, when chain4 is unvaried, lowest 2 bits of regard access address hand-picked the even, and the address is shifted 2 bits down. As such, I hit upon on it praisefully improbable that the facts fashionable chain4 permit underneath is annul. [[User:Mystran|Mystran]] 09:25, 9 December 2007 (CST)
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” Here’s the board: all systems emulate fashion 0Ч13 and mode-x up to the enormousness most programmers do as read. When in fashion 0Ч13, video regard seems linear strictly to the confine 4 granule. dword fashion respecting 0Ч13 and byte fashion respecting mode-x. On the other aimless, selecting the corresponding byte-mode, word-mode and dword-mode for the spread attempt up as skedaddle onto, i.e.
It means that when you profit by no more than a certain fashion there’s nothing diabolical. However, bochs does not permit the b/w/d-mode bits and as a substitute for uses the chain-4 granule to put down on the opting for. QEmu doesn’t permit these bits either, but in any anyway a lest uses byte fashion and redirects the writes in chain-4 enabled fashion to the picture needed to enjoy byte data between engagements as expected. All the tested emulators enjoy their quirks in this debar, assuming that the authentic cards are the most VGA compatible.
