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More COMPAQ information

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This commit is contained in:
Jeff Parsons 2016-02-24 15:43:32 -08:00
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devices/pc/rom/compaq/bios/deskpro386/README.md
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@ -1,21 +1,22 @@
---
layout: page
title: Compaq DeskPro 386 ROMs
title: COMPAQ DeskPro 386 ROMs
permalink: /devices/pc/rom/compaq/bios/deskpro386/
redirect_from:
- /devices/pc/bios/compaq/deskpro386/
---
Compaq DeskPro 386 ROMs
COMPAQ DeskPro 386 ROMs
---
The oldest Compaq DeskPro 386 ROM I have is a Rev J.4 ROM from a "Version 2" motherboard designed
The oldest COMPAQ DeskPro 386 ROM I have is a Rev J.4 ROM from a "Version 2" motherboard designed
in 1987 and released in 1988.
[<img src="http://archive.pcjs.org/pubs/pc/reference/compaq/images/Compaq_DeskPro_386-16_System_Board_V2-640.jpg" alt="Compaq DeskPro 386 System Board Version 2"/>](http://archive.pcjs.org/pubs/pc/reference/compaq/images/Compaq_DeskPro_386-16_System_Board_V2.jpg)
Thanks to folks on the [Vintage Computer](http://www.vintage-computer.com/) forums, I also have a Rev N.1 ROM from 1989.
However, I'm still on the lookout for any "Version 1" motherboards from 1986, so that I can obtain dumps of Compaq's
However, I'm still on the lookout for any "Version 1" motherboards from 1986, so that I can obtain dumps of COMPAQ's
ROMs for their earliest 80386-based systems.
### System ROM Locations on COMPAQ DESKPRO 386 System Board Version 2 (Assembly No. 000558-001)
@ -58,22 +59,23 @@ from the two 16Kb BIN files provided by [Al Kossow](http://www.vintage-computer.
Dumping the ROMs
---
The *.hex* files for the 1988-01-28 DeskPro ROM were produced by running [eeprom_read](http://github.com/phooky/PROM/blob/master/tools/eeprom_read/eeprom_read.pde)
on a [chipKIT Uno32](http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,892,893&Prod=CHIPKIT-UNO32) Arduino-compatible
prototyping board, and capturing the serial port output on my MacBook Pro -- as outlined in
The *.hex* files for the 1988-01-28 DeskPro ROM were produced by running
[eeprom_read](http://github.com/phooky/PROM/blob/master/tools/eeprom_read/eeprom_read.pde)
on a [chipKIT Uno32](http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,892,893&Prod=CHIPKIT-UNO32)
Arduino-compatible prototyping board, and capturing the serial port output on my MacBook Pro -- as outlined in
"[Stick a Straw in Its Brain and Suck: How to Read a ROM](http://www.nycresistor.com/2012/07/07/stick-a-straw-in-its-brain-and-suck-how-to-read-a-rom/)"
by [NYC Resistor](http://www.nycresistor.com/) contributor [phooky](http://www.nycresistor.com/author/phooky/).
The DeskPro 386 ROMs were P27128A-2 chips, so I wired my Uno32 based on this [27128A](http://archive.pcjs.org/pubs/pc/datasheets/27128A.pdf)
datasheet -- the closest match I could find online.
The DeskPro 386 ROMs were P27128A-2 chips, so I wired my Uno32 based on this
[27128A](http://archive.pcjs.org/pubs/pc/datasheets/27128A.pdf) datasheet -- the closest match I could find online.
![<img src="http://archive.pcjs.org/pubs/pc/reference/compaq/images/Compaq_DeskPro_386-16_System_ROM_V2_Breadboard-640.jpg" alt="Compaq DeskPro 386 System ROM Version 2"/>](http://archive.pcjs.org/pubs/pc/reference/compaq/images/Compaq_DeskPro_386-16_System_ROM_V2_Breadboard.jpg)
On my first dump attempt, every ROM address returned 0xFF. After looking at the 27128A datasheet more closely, I noticed
the DEVICE OPERATION table indicated that, for a READ operation, /CE and /OE pins should be connected to INPUT LOW VOLTAGE,
while the /PGM should be connected to INPUT HIGH VOLTAGE. So I wired pin 27 (/PGM) to +5V instead of GND, and the dump
worked perfectly. The NYC Resistor article implied that every *active low* pin should be connected to GND, but apparently
there are exceptions to that general rule.
On my first dump attempt, every ROM address returned 0xFF. After looking at the 27128A datasheet more closely,
I noticed the DEVICE OPERATION table indicated that, for a READ operation, /CE and /OE pins should be connected to
INPUT LOW VOLTAGE, while the /PGM should be connected to INPUT HIGH VOLTAGE. So I wired pin 27 (/PGM) to +5V instead
of GND, and the dump worked perfectly. The NYC Resistor article implied that every *active low* pin should be
connected to GND, but apparently there are exceptions to that general rule.
Recreating ROM Source Code
---
@ -104,7 +106,7 @@ However, it does NOT produce a binary identical to the original ROM, in part bec
instructions that can be assembled multiple ways). It's possible the reassembled ROM may still work, but more research
is required.
One interesting section of the Compaq DeskPro ROM is this string at offset 0xE002:
One interesting section of the COMPAQ DeskPro ROM is this string at offset 0xE002:
db 'AUTHORS CAB93GLB93RWS93DJC93NPB(C)Copyright COMPAQ Computer Corporation 1982,83,84,85,86'