ZealOS/docs/Doc/MemoryOverview.DD

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<a name="l1"></a><span class=cF5>                                                        Memory Overview</span><span class=cF0>
<a name="l2"></a>
<a name="l3"></a>Paging is practically not used.  64-bit mode requires paging, however, so it is identity-mapped -- virtual identical to 
<a name="l4"></a>physical.  All tasks on all cores use the same page table map, just as though all addresses are physical addresses.  2Meg or 
<a name="l5"></a>1Gig page table entries are used.   Nothing swaps to disk.
<a name="l6"></a>
<a name="l7"></a>In ZealOS, the lowest 2Gig of memory is called the </span><span class=cF2>code heap</span><span class=cF0>.  ZealOS's compiler always uses 32-bit signed relative JMP &amp; CALL 
<a name="l8"></a>insts because 64-bit CALLs take two insts.  With signed +/- 32-bit values, code can only call a function within 2Gig distance.  
<a name="l9"></a>Therefore, ZealOS keeps all code in the lowest 2Gig memory addresses including what would normally be called &quot;the kernel&quot;.  Two 
<a name="l10"></a>Gig is plenty for code, don't worry.
<a name="l11"></a>
<a name="l12"></a>You can create new, independent heaps using </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/HeapCtrl.html#l1"><span class=cF4>HeapCtrlInit</span></a><span class=cF0>(). Then, use the </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KernelA.html#l3527"><span class=cF4>CHeapCtrl</span></a><span class=cF0> as the 2nd arg to </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l391"><span class=cF4>MAlloc</span></a><span class=cF0>(). See </span><a href="https://tomawezome.github.io/ZealOS/System/Utils/HeapLog.html#l83"><span class=cF4>HeapLog</span></a><span class=cF0>() 
<a name="l13"></a>for an example.
<a name="l14"></a>
<a name="l15"></a>Memory alloced by a task will be freed when the task is killed.  The </span><a href="https://tomawezome.github.io/ZealOS/Doc/Glossary.html#l154"><span class=cF4>System Task</span></a><span class=cF0> is a task that never dies. His memory is like 
<a name="l16"></a>kernel memory in other operating systems.   See </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l408"><span class=cF4>ZCAlloc</span></a><span class=cF0>(), </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l394"><span class=cF4>ZMAlloc</span></a><span class=cF0>(), </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l427"><span class=cF4>ZMAllocIdent</span></a><span class=cF0>() and </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l503"><span class=cF4>ZStrNew</span></a><span class=cF0>().
<a name="l17"></a>
<a name="l18"></a>All of the regular page tables are marked, &quot;cached&quot;.    When accessing hardware, however, you need uncached page table.  The 
<a name="l19"></a>lowest 4Gig addresses have an alias to access hardware located toward the top of mapped space, </span><span class=cF2>0x0140000000</span><span class=cF0>.    See </span><span class=cF4>
<a name="l20"></a></span><a href="https://tomawezome.github.io/ZealOS/Kernel/MultiProc.html#l147"><span class=cF4>dev.uncached_alias</span></a><span class=cF0>.
<a name="l21"></a>
<a name="l22"></a>During an extended powered-on session of ZealOS, in theory, memory will become fragmented, requiring a reboot.  It has never 
<a name="l23"></a>happens to me.
<a name="l24"></a>
<a name="l25"></a>See </span><a href="https://tomawezome.github.io/ZealOS/System/Utils/MemRep.html#l219"><span class=cF4>MemRep</span></a><span class=cF0>() and </span><a href="https://tomawezome.github.io/ZealOS/Demo/MemDemo.html#l1"><span class=cF4>::/Demo/MemDemo.CC</span></a><span class=cF0>.
<a name="l26"></a>
<a name="l27"></a>
<a name="l28"></a></span><span class=cF5>                                                 Single System-wide Memory Map
<a name="l29"></a>
<a name="l30"></a></span><span class=cF2> 0x0000007C00- 0x000003707F</span><span class=cF0>
<a name="l31"></a>  Kernel module, placed here by the boot-loader, </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KernelA.html#l4439"><span class=cF4>BOOT_RAM_BASE</span></a><span class=cF0>.
<a name="l32"></a>
<a name="l33"></a></span><span class=cF2> 0x0000096600- 0x0000096FFF</span><span class=cF0>
<a name="l34"></a>  Boot block relocated here before loading the Kernel module, </span><a href="https://tomawezome.github.io/ZealOS/System/Boot/BootDVD.html#l1"><span class=cF4>BootDVD</span></a><span class=cF0> &amp; </span><a href="https://tomawezome.github.io/ZealOS/System/Boot/BootHD.html#l1"><span class=cF4>BootHD</span></a><span class=cF0>.
<a name="l35"></a>
<a name="l36"></a></span><span class=cF2> 0x0000097000- 0x0000097030</span><span class=cF0> Multicore start-up vect code, </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KernelA.html#l664"><span class=cF4>MPN_VECT</span></a><span class=cF0>.
<a name="l37"></a></span><span class=cF2>~0x000009F000- 0x000009FFFF</span><span class=cF0> Extended BIOS data area.
<a name="l38"></a></span><span class=cF2> 0x00000A0000- 0x00000BFFFF</span><span class=cF0> VGA graphics mem with alias at </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KGlobals.html#l30"><span class=cF4>text</span></a><span class=cF0>.vga_alias.
<a name="l39"></a></span><span class=cF2> 0x0000100000- 0x0000101FFF</span><span class=cF0> </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KernelA.html#l4082"><span class=cF4>CSysFixedArea</span></a><span class=cF0> for misc.
<a name="l40"></a></span><span class=cF2> 0x0000104000- 0x0037ADFCFF</span><span class=cF0> Code Heap mem.
<a name="l41"></a>
<a name="l42"></a></span><span class=cF2> 0x00E0000000- 0x00FFFFFFFF</span><span class=cF0>
<a name="l43"></a>  32-bit devices could alloc memory at 0xF0000000 going up, but this is wrong, since some PCs already have devices at 
<a name="l44"></a>  0xF0000000.  PCI devices are supported, so </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MemPhysical.html#l64"><span class=cF4>Mem32DevAlloc</span></a><span class=cF0>() flaws could become an issue.
<a name="l45"></a>
<a name="l46"></a></span><span class=cF2> 0x0080000000-~0x00DFFFFFFF</span><span class=cF0>
<a name="l47"></a></span><span class=cF2> 0x0100000000-~0x011EBFFFFF</span><span class=cF0>
<a name="l48"></a>  Data Heap mem.    (The physical memory that exists in this range is data heap.)
<a name="l49"></a>
<a name="l50"></a></span><span class=cF2> 0x0140000000- 0x023FFFFFFF</span><span class=cF0>
<a name="l51"></a>  Uncached alias of first 4Gig.  (For 32-bit device access.)
<a name="l52"></a>
<a name="l53"></a></span><span class=cF2>                         - 0x023FFFFFFF</span><span class=cF0>
<a name="l54"></a>  64-bit devices are alloced with </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MemPhysical.html#l122"><span class=cF4>Mem64DevAlloc</span></a><span class=cF0>() counting backward.
<a name="l55"></a>
<a name="l56"></a>
<a name="l57"></a>
<a name="l58"></a>* Note: There is a break in the data-heap block pool.  This has no effect except the obvious effect that fragmentation has on 
<a name="l59"></a>contiguous requests.    You can </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l391"><span class=cF4>MAlloc</span></a><span class=cF0>() an 8Gig chunk on a 12Gig machine.  You can </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l391"><span class=cF4>MAlloc</span></a><span class=cF0>() a 32Gig chunk on a 64Gig machine.
<a name="l60"></a>
<a name="l61"></a>* Note: For systems with less than 2Gig RAM, the code and data heap block pools are the same.  For systems with 2-4Gig of RAM, 
<a name="l62"></a>the code heap is 1/4 of the total.  See </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/BlkPool.html#l31"><span class=cF4>BlkPoolsInit</span></a><span class=cF0>().
<a name="l63"></a>
<a name="l64"></a>
<a name="l65"></a></span><span class=cF5>                                                            History</span><span class=cF0>
<a name="l66"></a>
<a name="l67"></a>In 2003, Terry Davis wanted to make a no-paging ring-0-only 64-bit operating system for super speed with simplicity and full 
<a name="l68"></a>access. With paging, every memory request requires 5 accesses -- it must access the address itself, 4K, 2Meg, 1Gig, and 512Gig 
<a name="l69"></a>page tables, but the CPU's translation look-aside buffer mostly removes the penalty for using paging.   So, he did not want to 
<a name="l70"></a>use paging, but long mode requires it.  He did the next best thing -- he identity-mapped everything and achieved the simplicity 
<a name="l71"></a>he was after with subtle performance boosts, not wasting time changing address maps.  We look forward to the day Intel makes an 
<a name="l72"></a>optimized no-paging long mode.
<a name="l73"></a>
<a name="l74"></a>Terry needed VGA A0000-BFFFF memory to be write-through and 0xE0000000-0xFFFFFFFF to be uncached for various devices.  All 
<a name="l75"></a>64-bit computers allow stopping address translation at 2Meg page size, not using 4K.  He wanted to use 2Meg for everything 
<a name="l76"></a>because it's faster, with one less level of page tables.  He had to make A0000-BFFFF write-through, though, so he could not use 
<a name="l77"></a>2Meg size on the lowest page.   He did the lowest 2Meg area as 4K pages.  He also unmapped the first 4K to cause a fault when 
<a name="l78"></a>dereferencing NULL.
<a name="l79"></a>
<a name="l80"></a>In 2016, Terry came-up with an alternate idea.  He double mapped the lowest memory with an alias that was uncached. Accessing 
<a name="l81"></a>the lowest 2Meg area directly was cached but the alias he created up at the top of address space was uncached.  See </span><span class=cF4>
<a name="l82"></a></span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MemPhysical.html#l157"><span class=cF4>UncachedAliasAlloc</span></a><span class=cF0>().  Unfortunately, he could no longer boast of the simplicity of identity mapping everything.  Since many of 
<a name="l83"></a>the users are familiar with A0000-BFFFF, it is actually pretty seriously unfortunate that they cannot use the easy-to-understand 
<a name="l84"></a>numbers of A0000-BFFFF, but must access the relocated alias location.   See </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KMain.html#l121"><span class=cF4>text.vga_alias</span></a><span class=cF0>.  We also no longer cause a fault 
<a name="l85"></a>when dereferencing NULL.
<a name="l86"></a>
<a name="l87"></a>Then, Terry switched to 1Gig page sizes.    For the lowest 4Gig, he set-up an alias up at the top of address space. See </span><span class=cF4>
<a name="l88"></a></span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MemPhysical.html#l157"><span class=cF4>UncachedAliasAlloc</span></a><span class=cF0>().   Not all computers support 1Gig page tables, however, so he also supported 2Meg.
<a name="l89"></a>
<a name="l90"></a>Terry's original plan was to allow changing the page tables as needed, so he had code for taking control of 2Meg pages and 
<a name="l91"></a>marking them uncached or whatever.  When he did an HDAudio driver, he requested some 32-bit address space as uncached.  Today, 
<a name="l92"></a>all of the first 4Gig can be accessed without caching at the </span><a href="https://tomawezome.github.io/ZealOS/Kernel/MultiProc.html#l147"><span class=cF4>dev.uncached_alias</span></a><span class=cF0>.
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Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<!DOCTYPE HTML>`
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Fix HTML generation on files with duplicate names but different extensions. 2021-07-05 01:12:38 +01:00			`<pre style="font-family:monospace;font-size:12pt">`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l1"></a><span class=cF5> Memory Overview</span><span class=cF0>`
			`<a name="l2"></a>`
			`<a name="l3"></a>Paging is practically not used. 64-bit mode requires paging, however, so it is identity-mapped -- virtual identical to`
			`<a name="l4"></a>physical. All tasks on all cores use the same page table map, just as though all addresses are physical addresses. 2Meg or`
Fix HTML index file generation. Fix HTML generation tab width. 2021-07-04 23:11:34 +01:00			`<a name="l5"></a>1Gig page table entries are used. Nothing swaps to disk.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l6"></a>`
			`<a name="l7"></a>In ZealOS, the lowest 2Gig of memory is called the </span><span class=cF2>code heap</span><span class=cF0>. ZealOS's compiler always uses 32-bit signed relative JMP & CALL`
			`<a name="l8"></a>insts because 64-bit CALLs take two insts. With signed +/- 32-bit values, code can only call a function within 2Gig distance.`
			`<a name="l9"></a>Therefore, ZealOS keeps all code in the lowest 2Gig memory addresses including what would normally be called "the kernel". Two`
			`<a name="l10"></a>Gig is plenty for code, don't worry.`
			`<a name="l11"></a>`
Fix HTML index file generation. Fix HTML generation tab width. 2021-07-04 23:11:34 +01:00			<a name="l12"></a>You can create new, independent heaps using </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/HeapCtrl.html#l1"><span class=cF4>HeapCtrlInit</span></a><span class=cF0>(). Then, use the </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KernelA.html#l3527"><span class=cF4>CHeapCtrl</span></a><span class=cF0> as the 2nd arg to </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l391"><span class=cF4>MAlloc</span></a><span class=cF0>(). See </span><a href="https://tomawezome.github.io/ZealOS/System/Utils/HeapLog.html#l83"><span class=cF4>HeapLog</span></a><span class=cF0>()
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l13"></a>for an example.`
			`<a name="l14"></a>`
Fix HTML index file generation. Fix HTML generation tab width. 2021-07-04 23:11:34 +01:00			`<a name="l15"></a>Memory alloced by a task will be freed when the task is killed. The </span><a href="https://tomawezome.github.io/ZealOS/Doc/Glossary.html#l154"><span class=cF4>System Task</span></a><span class=cF0> is a task that never dies. His memory is like`
			<a name="l16"></a>kernel memory in other operating systems. See </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l408"><span class=cF4>ZCAlloc</span></a><span class=cF0>(), </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l394"><span class=cF4>ZMAlloc</span></a><span class=cF0>(), </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l427"><span class=cF4>ZMAllocIdent</span></a><span class=cF0>() and </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l503"><span class=cF4>ZStrNew</span></a><span class=cF0>().
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l17"></a>`
			`<a name="l18"></a>All of the regular page tables are marked, "cached". When accessing hardware, however, you need uncached page table. The`
Fix codebase HTML generation. 2021-07-03 07:47:45 +01:00			`<a name="l19"></a>lowest 4Gig addresses have an alias to access hardware located toward the top of mapped space, </span><span class=cF2>0x0140000000</span><span class=cF0>. See </span><span class=cF4>`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l20"></a></span><a href="https://tomawezome.github.io/ZealOS/Kernel/MultiProc.html#l147"><span class=cF4>dev.uncached_alias</span></a><span class=cF0>.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l21"></a>`
			`<a name="l22"></a>During an extended powered-on session of ZealOS, in theory, memory will become fragmented, requiring a reboot. It has never`
			`<a name="l23"></a>happens to me.`
			`<a name="l24"></a>`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l25"></a>See </span><a href="https://tomawezome.github.io/ZealOS/System/Utils/MemRep.html#l219"><span class=cF4>MemRep</span></a><span class=cF0>() and </span><a href="https://tomawezome.github.io/ZealOS/Demo/MemDemo.html#l1"><span class=cF4>::/Demo/MemDemo.CC</span></a><span class=cF0>.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l26"></a>`
			`<a name="l27"></a>`
			`<a name="l28"></a></span><span class=cF5> Single System-wide Memory Map`
			`<a name="l29"></a>`
Implement OS Upgrade wizard. Make HTML doc generation force index files to make links from subdirectories. Added Sixto-Clementine Vulgate Bible to Misc/. Fix User window height, patch font chars. 2021-07-04 06:19:15 +01:00			`<a name="l30"></a></span><span class=cF2> 0x0000007C00- 0x000003707F</span><span class=cF0>`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l31"></a> Kernel module, placed here by the boot-loader, </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KernelA.html#l4439"><span class=cF4>BOOT_RAM_BASE</span></a><span class=cF0>.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l32"></a>`
			`<a name="l33"></a></span><span class=cF2> 0x0000096600- 0x0000096FFF</span><span class=cF0>`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l34"></a> Boot block relocated here before loading the Kernel module, </span><a href="https://tomawezome.github.io/ZealOS/System/Boot/BootDVD.html#l1"><span class=cF4>BootDVD</span></a><span class=cF0> & </span><a href="https://tomawezome.github.io/ZealOS/System/Boot/BootHD.html#l1"><span class=cF4>BootHD</span></a><span class=cF0>.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l35"></a>`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l36"></a></span><span class=cF2> 0x0000097000- 0x0000097030</span><span class=cF0> Multicore start-up vect code, </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KernelA.html#l664"><span class=cF4>MPN_VECT</span></a><span class=cF0>.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l37"></a></span><span class=cF2>~0x000009F000- 0x000009FFFF</span><span class=cF0> Extended BIOS data area.`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l38"></a></span><span class=cF2> 0x00000A0000- 0x00000BFFFF</span><span class=cF0> VGA graphics mem with alias at </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KGlobals.html#l30"><span class=cF4>text</span></a><span class=cF0>.vga_alias.`
			`<a name="l39"></a></span><span class=cF2> 0x0000100000- 0x0000101FFF</span><span class=cF0> </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KernelA.html#l4082"><span class=cF4>CSysFixedArea</span></a><span class=cF0> for misc.`
Implement OS Upgrade wizard. Make HTML doc generation force index files to make links from subdirectories. Added Sixto-Clementine Vulgate Bible to Misc/. Fix User window height, patch font chars. 2021-07-04 06:19:15 +01:00			`<a name="l40"></a></span><span class=cF2> 0x0000104000- 0x0037ADFCFF</span><span class=cF0> Code Heap mem.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l41"></a>`
			`<a name="l42"></a></span><span class=cF2> 0x00E0000000- 0x00FFFFFFFF</span><span class=cF0>`
			`<a name="l43"></a> 32-bit devices could alloc memory at 0xF0000000 going up, but this is wrong, since some PCs already have devices at`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l44"></a> 0xF0000000. PCI devices are supported, so </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MemPhysical.html#l64"><span class=cF4>Mem32DevAlloc</span></a><span class=cF0>() flaws could become an issue.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l45"></a>`
			`<a name="l46"></a></span><span class=cF2> 0x0080000000-~0x00DFFFFFFF</span><span class=cF0>`
Implement OS Upgrade wizard. Make HTML doc generation force index files to make links from subdirectories. Added Sixto-Clementine Vulgate Bible to Misc/. Fix User window height, patch font chars. 2021-07-04 06:19:15 +01:00			`<a name="l47"></a></span><span class=cF2> 0x0100000000-~0x011EBFFFFF</span><span class=cF0>`
Fix HTML index file generation. Fix HTML generation tab width. 2021-07-04 23:11:34 +01:00			`<a name="l48"></a> Data Heap mem. (The physical memory that exists in this range is data heap.)`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l49"></a>`
Fix codebase HTML generation. 2021-07-03 07:47:45 +01:00			`<a name="l50"></a></span><span class=cF2> 0x0140000000- 0x023FFFFFFF</span><span class=cF0>`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l51"></a> Uncached alias of first 4Gig. (For 32-bit device access.)`
			`<a name="l52"></a>`
Fix HTML index file generation. Fix HTML generation tab width. 2021-07-04 23:11:34 +01:00			`<a name="l53"></a></span><span class=cF2> - 0x023FFFFFFF</span><span class=cF0>`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l54"></a> 64-bit devices are alloced with </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MemPhysical.html#l122"><span class=cF4>Mem64DevAlloc</span></a><span class=cF0>() counting backward.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l55"></a>`
			`<a name="l56"></a>`
			`<a name="l57"></a>`
			`<a name="l58"></a>* Note: There is a break in the data-heap block pool. This has no effect except the obvious effect that fragmentation has on`
Fix HTML index file generation. Fix HTML generation tab width. 2021-07-04 23:11:34 +01:00			`<a name="l59"></a>contiguous requests. You can </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l391"><span class=cF4>MAlloc</span></a><span class=cF0>() an 8Gig chunk on a 12Gig machine. You can </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MAllocFree.html#l391"><span class=cF4>MAlloc</span></a><span class=cF0>() a 32Gig chunk on a 64Gig machine.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l60"></a>`
			`<a name="l61"></a>* Note: For systems with less than 2Gig RAM, the code and data heap block pools are the same. For systems with 2-4Gig of RAM,`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l62"></a>the code heap is 1/4 of the total. See </span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/BlkPool.html#l31"><span class=cF4>BlkPoolsInit</span></a><span class=cF0>().`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l63"></a>`
			`<a name="l64"></a>`
			`<a name="l65"></a></span><span class=cF5> History</span><span class=cF0>`
			`<a name="l66"></a>`
			`<a name="l67"></a>In 2003, Terry Davis wanted to make a no-paging ring-0-only 64-bit operating system for super speed with simplicity and full`
			`<a name="l68"></a>access. With paging, every memory request requires 5 accesses -- it must access the address itself, 4K, 2Meg, 1Gig, and 512Gig`
			`<a name="l69"></a>page tables, but the CPU's translation look-aside buffer mostly removes the penalty for using paging. So, he did not want to`
			`<a name="l70"></a>use paging, but long mode requires it. He did the next best thing -- he identity-mapped everything and achieved the simplicity`
			`<a name="l71"></a>he was after with subtle performance boosts, not wasting time changing address maps. We look forward to the day Intel makes an`
			`<a name="l72"></a>optimized no-paging long mode.`
			`<a name="l73"></a>`
			`<a name="l74"></a>Terry needed VGA A0000-BFFFF memory to be write-through and 0xE0000000-0xFFFFFFFF to be uncached for various devices. All`
			`<a name="l75"></a>64-bit computers allow stopping address translation at 2Meg page size, not using 4K. He wanted to use 2Meg for everything`
			`<a name="l76"></a>because it's faster, with one less level of page tables. He had to make A0000-BFFFF write-through, though, so he could not use`
			`<a name="l77"></a>2Meg size on the lowest page. He did the lowest 2Meg area as 4K pages. He also unmapped the first 4K to cause a fault when`
			`<a name="l78"></a>dereferencing NULL.`
			`<a name="l79"></a>`
Fix HTML index file generation. Fix HTML generation tab width. 2021-07-04 23:11:34 +01:00			`<a name="l80"></a>In 2016, Terry came-up with an alternate idea. He double mapped the lowest memory with an alias that was uncached. Accessing`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l81"></a>the lowest 2Meg area directly was cached but the alias he created up at the top of address space was uncached. See </span><span class=cF4>`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l82"></a></span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MemPhysical.html#l157"><span class=cF4>UncachedAliasAlloc</span></a><span class=cF0>(). Unfortunately, he could no longer boast of the simplicity of identity mapping everything. Since many of`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l83"></a>the users are familiar with A0000-BFFFF, it is actually pretty seriously unfortunate that they cannot use the easy-to-understand`
Implement OS Upgrade wizard. Make HTML doc generation force index files to make links from subdirectories. Added Sixto-Clementine Vulgate Bible to Misc/. Fix User window height, patch font chars. 2021-07-04 06:19:15 +01:00			`<a name="l84"></a>numbers of A0000-BFFFF, but must access the relocated alias location. See </span><a href="https://tomawezome.github.io/ZealOS/Kernel/KMain.html#l121"><span class=cF4>text.vga_alias</span></a><span class=cF0>. We also no longer cause a fault`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l85"></a>when dereferencing NULL.`
			`<a name="l86"></a>`
Fix HTML index file generation. Fix HTML generation tab width. 2021-07-04 23:11:34 +01:00			`<a name="l87"></a>Then, Terry switched to 1Gig page sizes. For the lowest 4Gig, he set-up an alias up at the top of address space. See </span><span class=cF4>`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l88"></a></span><a href="https://tomawezome.github.io/ZealOS/Kernel/Memory/MemPhysical.html#l157"><span class=cF4>UncachedAliasAlloc</span></a><span class=cF0>(). Not all computers support 1Gig page tables, however, so he also supported 2Meg.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`<a name="l89"></a>`
			`<a name="l90"></a>Terry's original plan was to allow changing the page tables as needed, so he had code for taking control of 2Meg pages and`
			`<a name="l91"></a>marking them uncached or whatever. When he did an HDAudio driver, he requested some 32-bit address space as uncached. Today,`
Fix codebase HTML generation. 2021-07-03 07:51:43 +01:00			`<a name="l92"></a>all of the first 4Gig can be accessed without caching at the </span><a href="https://tomawezome.github.io/ZealOS/Kernel/MultiProc.html#l147"><span class=cF4>dev.uncached_alias</span></a><span class=cF0>.`
Implement codebase HTML generation. 2021-07-03 05:07:57 +01:00			`</span></pre></body>`
			`</html>`