---------------------------------------------------------------------------- Copyright (c) Carl W. Houseman, 1985. All rights reserved. ---------------------------------------------------------------------------- Restoring Auto- and Floppy- Boot with the NEC V20 Processor -------------------------------- An easy way to get some additional computing power out of your Rainbow is to install an NEC V20 (uPD70108) microprocessor in place of Intel's 8088 processor. Unfortunately, the Rainbow firmware is not prepared for the faster V20, and self test fails. The result is that 100B/100+ systems will not auto-boot (the Winchester can still be booted manually), and boot from floppy is impossible in all models. You can restore the auto-boot and floppy boot capability to your system by making a modified copy of the rom containing the self-test and boot firmware. NOTE, HOWEVER, THAT DEC's COPYRIGHT NOTICE PREVENTS YOU FROM MAKING COPIES FOR ANYONE BUT YOURSELF. The rom modificatons should work for versions 04.03.11A of the 100A, and 05.03A of 100B/100+ boot firmware (the first number before the "." identifies the boot rom). However, subtle differences may exist in the boot rom without an external version number change, so before removing the rom, check for the correct version as follows: 1. Start DEBUG at the MS-DOS prompt 2. Enter one of the following DEBUG commands, depending on your system: 100A: 100B/100+: D FA00:1FFE 1FFF D F400:3FFE 3FFF 3. You should see: FA00:1FF0 91 B2 F400:3FF0 47 A0 (extra spaces in the display and trailing characters not shown here) If you have the correct version, you'll need a blank 2764 (100A) or 27128 (100B/100+) eprom for the copy, plus access to the following equipment: o A prom programmer/duplicator which allows specific prom locations to be changed for a duplicate operation o A small flat blade screwdriver o A chip extractor (preferred to a screwdriver for 100B/100+) o The Pocket Service Guide (EK-PC100-PS-002) or Technical Manual Addendum (EK-RB100-TM-001) Disassemble the system and remove the boot rom, being very careful with the socket in 100A systems as noted in the technical documentation. Set up the prom programmer to program the locations with data as indicated (all hexadecimal): 100A: 100B/100+: Location Data Location Data 043F 64 072F 64 067D 20 0B36 20 1FFE 2B 3FFE 1B 1FFF 70 3FFF 88 When you replace the 8088 with a V20, replace the boot rom at the same time. The modified rom will not work with the 8088 installed. I'd like to hear from anyone who succesfully modifies a 100A prom, since only the 100B version has been tested. If your boot rom fails the version check, give me a call to discuss the details of making the changes to a different rom version. Carl Houseman 703-337-4565 (evenings) ----------------------------------------------------------------------------- Comments on the text by Tom F Karlsson 4-SEP-1993: This file was sent to me by Nigel W. Johnson and I now contribute it to the ftp area of ftp.update.uu.se. Nigel confirmed that the patch also works with a 100A model. If you have problems locating the right EPROM and doesn't have a manual describing which EPROM to modify, you can always mark them all (to be sure that you insert them correctly later in their proper places) and pull them all out. Then use the EPROM reader/burner to read the two last positions in each EPROM. The right one should say '91 B2' for a 100A and '47 A0' for a 100B/+. On 100B models (I only have B models), the right PROM is the one closest to the front of the machine (of the two PROMs located near the 8088 cpu). /Tom (tomk@update.uu.se)