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IBM PC Family  -  Some documentation errors



Date August 1981
Document IBM 5150 - Technical Reference - First Edition (August 1981)
Page 2-8
Error "and require five clocks or approximately 7% of the bus bandwidth." should be,
"and require four clocks or approximately 5.6% of the bus bandwidth".
Notes • Per page 2-4, refresh DMA cycles are 4 clocks long.
• 4 clocks in 72 equates to 5.6%
• The clock count portion has been corrected in later editions of the manual.



Date August 1981
Document IBM 5150 - Technical Reference - First Edition (August 1981)
Page 2-36
Error "for a maximum of 5 seconds" should be,
"for a minimum of 5 seconds".
Note Seen fixed in the 1984 edition of the manual.



Date April 1983
Document IBM 5150 - Technical Reference - Revised Edition (July 1982)
Page Page D-10   (System Board - Logic 11 of 12)
Background U80, a 74LS125, contains four tri-state buffers.
Error The buffer in U80 that has its output pin connected to the Keyboard Clock ('KYB CLK') line, has its output pin incorrectly labelled as pin 1.  It should be pin 11.



Date April 1983
Document IBM 5160 - Technical Reference - Revised Edition (April 1983)
Page 1-14
Error "and require four clocks or approximately 7% of the bus bandwidth." should be,
"and require four clocks or approximately 5.6% of the bus bandwidth".
Note • 4 clocks in 72 equates to 5.6%, not 7%
• Seen corrected in 'Revised Edition (March 1986)' edition of the 5155/5160 tech. ref.



Date April 1983
Document IBM 5160 - Technical Reference - Revised Edition (April 1983)
Page 1-67
Error In the diagram, the connection from the Keyboard Clock ('KYB CLK') line to the 74LS175 is incorrect.  The Keyboard Clock ('KYB CLK') line should be shown as being connected to the 'D' pin of the 74LS175's first flip-flop.



Date April 1983
Document IBM 5160 - Technical Reference - Revised Edition (April 1983)
Page Page D-4   (System Board - Sheet 3 of 10)
Error The signal coming into pin 10 of U57 is labeled as "MEMR".
That is incorrect.
The signal is YMEMR (which is MEMR that has been suitably delayed).
Note Seen corrected in 'Revised Edition (March 1986)' edition of the 5155/5160 tech. ref.



Date January 1984
Document IBM 5155 - Guide to Operations - First Edition (January 1984)
Page 4-81
Error Wrongly indicates that for 256 KB of motherboard RAM, switch 3 is set off and switch 4 is set on.
The correct information is that on an IBM 5155 motherboard, both switches 3 and 4 must be set off for 256 KB (i.e. all four RAM banks enabled).
Comment AST refers to this error in the third paragraph of here.



Date March 1984
Document IBM 5170 - Technical Reference - First Edition (March 1984)
Page 1-77
Error Click here to see.



Date April 1984
Document IBM 5150 - Technical Reference - Revised Edition (April 1984)
Page 1-15
Error "and require four clocks or approximately 7% of the bus bandwidth." should be,
"and require four clocks or approximately 5.6% of the bus bandwidth".
Note 4 clocks in 72 equates to 5.6%, not 7%



Date April 1984
Document IBM 5150 - Technical Reference - Revised Edition (April 1984)
Page 1-37
Error 1. /IOR, /IOW, /MEMR, and /MEMW lines mixed up.
2. Shown values of RN1 and RN3 are incorrect.
Note See here.



Date April 1984
Document IBM 5150 - Technical Reference - Revised Edition (April 1984)
Page 1-45
Error Part of the circuit diagram around chip U23 is incorrect.  See here.
Note Good in the earlier edition of the manual (for the earlier type of motherboard).



Date April 1984
Document IBM 5150 - Technical Reference - Revised Edition (April 1984)
Page 4-4
Error In the diagram, the connection from the Keyboard Clock ('KYB CLK') line to the 74LS175 is incorrect.  The Keyboard Clock ('KYB CLK') line should be shown as being connected to the 'D' pin of the 74LS175's first flip-flop.
Note Diagram in the 'First Edition (August 1981)' edition is correct.



Date August 1984
Document IBM Options and Adapters - IBM Monochrome Display
Pages 6 and 7  (circuit diagrams)
Error In the diagrams, pins 2 and 3 on IC601 are around the wrong way.  Click here to see my correction (in red).



Date August 1984
Document IBM Options and Adapters - IBM Monochrome Display and Printer Adapter
Page 26  (sheet 8 of circuit diagram)
Error In the diagram, pins 12 and 13 on U38 are around the wrong way.  Click here to see my correction (in red).



Date August 1984
Document IBM Options and Adapters - IBM Printer Adapter
Page Pages 4 and 5
Error • On page 4, the two occurences of '3BC' should be '378'.
• On page 5, '3BE' should be '37A'.
Comment I can see how this happened.  The author has used text in the 'IBM Monochrome Display and Printer Adapter' document as a template, failing to change all occurences of the port numbers.



Date August 1984
Document IBM Options and Adapters - Serial/Parallel Adapter
Page 20
Error In the diagram, the port numbers are swapped.  Click here to see my correction (in red).



Date September 1985
Document IBM 5170 - Technical Reference - First Edition (September, 1985)
Page 1-4
Error #1 Indicates that a type 1 motherboard has 4 banks of RAM
On a type 1 motherboard, there are only 2 banks, as indicated by the photo at here.

Note: IBM has the bank count correct in the MAR84 edition.
Error #2 Indicates that a type 2 motherboard has 2 banks of RAM
On a type 2 motherboard, there is only 1 bank  (where 1 bank = 16 data chips + 2 parity chips).



Date March 1986
Document IBM 5155/5160 - Technical Reference - Revised Edition (March 1986)
Pages x and 5-1
Error Refers to a '11/22/85' BIOS.  That should be '01/10/86' instead.



Date March 1986
Document IBM 5155/5160 - Technical Reference - Revised Edition (March 1986)
Pages 1-37 and 1-49
Error The pin numbering of the delay line is wrong.
Left to right, it should be 12,4,10,6,8 per the 14-pin diagram at here.
Note Other manuals have it correct.



Date March 1986
Document IBM 5155/5160 - Technical Reference - Revised Edition (March 1986)
Page 4-5
Error In the diagram, the connection from the Keyboard Clock ('KYB CLK') line to the 74LS175 is incorrect.  The Keyboard Clock ('KYB CLK') line should be shown as being connected to the 'D' pin of the 74LS175's first flip-flop.



Date March 1986
Document IBM 5170 - Technical Reference - Revised Edition (March, 1986)
Page 1-4
Error #1 Indicates that a type 1 motherboard has 4 banks of RAM
On a type 1 motherboard, there are only 2 banks, as indicated by the photo at here.

Note: IBM has the bank count correct in the MAR84 edition.
Error #2 Indicates that a type 2 motherboard has 2 banks of RAM
On a type 2 motherboard, there is only 1 bank  (where 1 bank = 16 data chips + 2 parity chips).



Date March 1986
Document • IBM 5170 - Technical Reference - First Edition (September, 1985)
• IBM 5170 - Technical Reference - Revised Edition (March, 1986)
Page 1-92
Error Click here to see.

Note: Shown correctly on a later page: page 1-113



Date ?????
Document IBM Options and Adapters - Color/Graphics Monitor Adapter (CGA)
Page 5
Error "16 bytes" should be, "16K bytes".



Date ?????
Document IBM Options and Adapters - Asynchronous Communications Adapter
Page 33
Error In the circuit diagram, jumper J13 is incorrectly labelled as J1.



Date March 1986
Document IBM Options and Adapters - 128KB/640KB Memory Expansion Option
Page 1
Error The 'Memory Module Location' diagram shows the wrong order of bits.



Date Various
Document Various for IBM 5150 and IBM 5160
Error Reports of IBM getting the switch setting wrong for the math coprocessor.
See here.



Date April 1983
Document IBM 5160 - Technical Reference - Revised Edition (April 1983)
Page Page D-11   (System Board - sheet 10 of 10)
Error ".047 PF" should be ".047 UF".
Based on the fact that the fitted capacitors have "473" printed on them.
Note Error also seen in other Technical Reference manuals for the 5160.



Date March 1986
Document IBM 5155/5160 - Technical Reference - Revised Edition (March 1986)
Page Page 1-56   (256/640K System Board - sheet 10 of 11)
Error ".047 PF" should be ".047 UF".
Based on the fact that the fitted capacitors have "473" printed on them.
Note Error also seen in other Technical Reference manuals for the 5160.



Date August 1986
Document IBM 5162 - Technical Reference - First Edition (August 1986)
Page Page 1-81   (System Board - sheet 5 of 22)
Error Pin numbering of J10 is incorrect.



Date ?????
Document Options and Adapters - IBM Expansion Unit
Page Circuit diagrams
Error Read the two 'Mistakes in the IBM Schematic' sections in the web page at here.



Date  
Documents • IBM 5170 - Technical Reference - First Edition (March 1984)
• IBM 5170 - Technical Reference - First Edition (September, 1985)
• IBM 5170 - Technical Reference - Revised Edition (March, 1986)
Section Source code listing for motherboard BIOS.
Page Page 5-59 of First Edition (March 1984)
Page 5-65 of First Edition (September, 1985)
Page 5-57 of Revised Edition (March, 1986)
Error Error in description of 203 error - see here.



Date Various
Documents Various
Issue Some incorrect representation of the 55,AA byte sequence.
See the web page at here.