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Aptiva - HIMEM.SYS cannot see above 64MB
Applicable to: World-Wide
Problem:
Customer has installed 64MB of RAM in his Aptiva in addition to the original 16MB that came with his system for a total of 80MB. His BIOS recognizes the 80MB of RAM, however, Windows 95 does not recognize any memory over 64MB (RAM). This is a limitation of HIMEM.SYS.
Solution:
HIMEM.SYS fails to report or use more than 64MB of installed memory on computers with an Industry Standard Architecture (ISA) or Micro Channel Architecture (MCA) bus. This is because ISA busses lack a standard BIOS interrupt routine for reporting more than 64MB of memory. HIMEM.SYS depends on the INT 15, function 88 service to determine installed memory, and this function is limited to 65,535 kilobytes (64MB).
MCA based computers add the INT 15, function C7 service to report installed memory. Although this function can report more than 64MB of memory, HIMEM.SYS has no code to support it . As a result, HIMEM.SYS uses the standard INT 15, function 88 call, which is also limited to 64MB of memory.
This limitation does not apply to computers with an Extended Industry Standard Architecture (EISA) bus. On EISA based computers, HIMEM.SYS scans each slot for device information, which means it can report up to 4GB.
Customer may need to use the /EISA switch on the HIMEM.SYS line in the CONFIG.SYS file. According to Windows 95 Unleashed, the maximum amount of memory addressable by Windows 95 is 4GB. Windows 95 makes use of a flat memory model. Native Windows 95 programs are able to use all addressable memory.
The problem with HIMEM.SYS exists in a virtual machine. Windows 95 virtual machines make use of HIMEM.SYS which does have the 64MB limitation imposed by INT 15 calls and the ISA bus. The machine is making use of all available memory.
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Search Keywords |
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Hint Category |
Windows 95, Memory | |
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Date Created |
26-12-96 | |
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Last Updated |
09-03-99 | |
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Revision Date |
09-03-2000 | |
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Brand |
IBM Aptiva | |
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Product Family |
Aptiva | |
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Machine Type |
2134, 2136, 2137, 2138, 2140, 2142, 2144, 2159, 2161, 2162, 2168, 2176 | |
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Model |
28R; 29R; 30R; 31R; 33R; 35R; 37R; 41R; 54S; 56S; 57S; 58S; B86; B87; B97; D81; D91; E81; E91; G86; G96; G97; H86; H96; P81; P91; Q3C; Q81; Q91; S35; S3C; S8C; S8H; S9C; S9H; S9M; SIB; U81; U91; V86; V96; X8C; X9D; 21R; 22R; 24R; 25R; 38R; 460; 461; 462; 471; C3D; C3E; C85; C8E; C8F; C8H; C8M; C8X; C9E; C9F; C9S; C9X; D34; D64; D84; E34 E64; E84; F34; F64; F84; G66; G76; H66; H76; J66; J76; L81; L91; M81; M91; N63; N64; N74; N81; N91; T71; T81; T84; T85; T8B; T8C; T8E; T8F; T94; T95; T9D; T9E; TAE; TAF; 13R; 14R; 15R; 16R; 17R; 18R; 19R; 20R; B60; B65; B75; B80; B85; B95; S64; S66; S74; S76; S78; S7H; S80; S90; S34; S35; S36; S44; S45; S46; S57; S61; S62; S67; S6F; S6H; S6S; SG1; SG2; SQ1; SQ2; SV1; SV2; L17; L27; L31; L35; L37; L3F; L44; L46; L45; L47; L51; L5H; L61; L6D; L71; L7M; LD2; LG2; LQ1; LQ2; LQ3; LQ4; LQ5; LQ6; LQ7; LV2; LG2; LG3; LG4; LV4; LG5; LV5; L66; L67; L87; ED1; ED3; E02; E03; E04; E05; E06; E10; E11; E12; E13; E14; E15; E16; E17; E18; E1F; E19; E20; E21; E22; E23; E24; E25; E26; E27; E28; E2F; E30; E31; E32; E33; E34; E35; E36; E37; E3F; E40; E41; E42; E43; E45; E46; E47; E4C; E4F; E50; E54; E64; E74; E84; E51; E53; E61; E63; E71; E73; EV1; EV3; EG1; EG3; E56; E5C; E76; E7C; E2H; E8F; E86; E8C; EL1; EK1; EL2; EK2; E80; E81; E82; E83; E48; E57; E58; EQ1; EQ2; EQ3; EQ4; EV1; EV3; EV5; EG1; EG3; EG6; E8S; E2C; E10; E11; E12; E13; E14; E15; E16; E20; E21; E22; E23; E24; E25; E26; E27; E30; E31; E32; E33; E34; E35; E36; E40; E42; E44; E45; E46; E54; E55; E56; E64; E65; E66; 351; 353; 361; 440; 445; 446; 6R6; C21; J31; J3A; J3X; J51; J52; JDA; JSN; K01; K21; K22; K23; K31; K32; K52; L01; L21; L22; L23; L31; L32; L52; L6T; P01; P21; P22; P23; P31; P32; P52; 352; 354; 355; 356; 357; 362; 363; 364; 372; 374; 381; 382; 384; 392; 442; 443; 447; 449; 454; 6R8; 6R9; 7R0; 7R1; 7R2; 7R3; 7R6; 7R7; 7R9; 8R1; 8R6; 8R8 ; 9R1; 9R2; 9R3; 9R4; 9R5; 9R6; C23; C31; C32; C33; C35; C3X; C53; C55; C5X; C65; C66; C67; C6B; C6D; C6E; C6V; C6X; C6Y; C6Z; C73; C77; C7X; F23; F31; F32; F33; F35; F67; F6B; H54; H55; H56; H5E; H5F; H64; H65; H6D; H6E; H6F; H7E; H7F; H7G; J33; J35; J3C; J3E; J3K; J3L; J3V; J3W; J3Y; J3Z; JCL; K53; J62; K74; L53; L62; P53; P62; T01; T33; T34; T62; T63; T65; T71; V34; V65; V71; W33; W55; W65; X01; X31; X33; X34; X52; X62; X63; X65; X71; Y01; Y04; Y31; Y33; Y34; Y52; Y62; Y63; Y65; Y71; Z01; Z31; Z33; Z34; Z52; Z62; Z63; Z65; Z71; M31; M41; M51; M52; M53; M55; M56; M57; M61; M62; M63; M71; M72; M91; 3R4; 3R5; 3R6; 4R1; 4R2; 2R9; 3R3; 3R1; 3R7; 4R0; 4R9; 3R9; 4R3; 5R5; A10; A12; A14; A40; A44; A45; A50; A51; A52; A90; A92; A94; 5R1; 6R3; 5R2; 5R3; 6R4; 5R4; 6R0; 5R6; 5R8; 5R9; 6R5; 9W2; 91W; 92W; 93W; 94W; 95W; 96W; 132; 142; 154; 162; 163; 172; 182; 121; 123; 131; 133; 141; 161; 171; LL2; L20; K20; KU6; LL4; L40; K40; KU4; LL6; L60; K60; L15; L16; K25; K26; L43; K43; L45; K45; KU5; L55; K55; L65; K65; L66; K66; U15; U16; W37; W47; N41; N51; N61; N71; S20; S55; S65; S64; S74; S75; S50; X10; Y10; Z10; X20; Y20; Z20; X30; Y30; Z30; X40; Y40; Z40; X37; X47; Y37; Y47; Z37; Z47; X17; X27; Y17; Y27; Z17; Z27 | |
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