52 lines
2.4 KiB
Markdown
52 lines
2.4 KiB
Markdown
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layout: page
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title: Compaq Portable Computer ROMs
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permalink: /devices/pcx86/rom/compaq/portable/
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---
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Compaq Portable Computer ROMs
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---
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The oldest COMPAQ Portable Computer ROM I have is an 8Kb [Rev C ROM](100666-001-REVC.json) from a REV D system board.
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[<img src="https://s3-us-west-2.amazonaws.com/archive.pcjs.org/pubs/pc/reference/compaq/images/COMPAQ_Portable_System_Board.jpg" alt="Compaq Portable System Board REV D"/>](https://s3-us-west-2.amazonaws.com/archive.pcjs.org/pubs/pc/reference/compaq/images/COMPAQ_Portable_System_Board-FULL.jpg)
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Printed on the back of the system board:
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(C) COMPAQ COMPUTER CORP. 1982
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BOARD NO. 000006-001 REV D 84490
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Curiously, the system board contains two mask ROMs (AM9265DPC), both labeled `1000666-001 REV.C` but with two different
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identifiers: `34569 8350KME` on the ROM in socket U40, and `34569 8350LME` on the ROM the socket below U40. However,
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when I dumped the ROMs with my homemade ROM reader, their contents were identical.
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I've seen pictures of other COMPAQ Portable system boards with only one mask ROM installed, so I'm puzzled as to why
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my board contains two. Do the contents of the second ROM show up in a different part of the address space? Unless
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I'm someday able to power and test this board, I may never know.
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Some clues can be found in this
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[COMPAQ Portable/Plus Maintenance Guide (Excerpt)](https://s3-us-west-2.amazonaws.com/archive.pcjs.org/pubs/pc/reference/compaq/portable/Compaq_Portable_Plus_Support_Discontinued.pdf).
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Older (REV B) system boards apparently *did* require 2 ROMs, at locations U40 and U47. REV C and later system boards
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required only 1 (REV C or later) ROM at location U40.
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That's all well and good, but it still doesn't explain why my REV D system board contains 2 ROMs. It just raises
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more questions. For example, why did *older* system boards require 2 ROMs? Were the earlier BIOS revisions larger
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or the ROMs smaller (eg, 4Kb instead of 8Kb)?
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Also, I've come across some other computer history sites that claim the COMPAQ Portable contained "12Kb" of ROM.
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Hmmm.
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### System ROM Revisions
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Thanks to the aforementioned Maintenance Guide excerpt, we know that these other COMPAQ Portable ROM revisions existed;
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however, REV C is the only revision currently available here.
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Rev ROM # Size Date
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--- ---------- ---- ----
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B 100518-001
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C 100666-001 8Kb None
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E 100298-004
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F 100298-005
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G 105681-001
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H 106265-001
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J 106265-002
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