Rainbows and NEC V20 upgrades.

Rainbow owners, I did get a request for the mods to make a Rainbow run with an NEC V20. Info below is from a reprint from the Rainbow News; unfortunately I don't have the date or the original issue, only the reprint. The article does carry the notation, Copyright (c) 1986 by Carl Houseman, all rights reserved, which means I'm probably about to get myself into potential legal trouble here. Carl, contact me if you are listening, I'll try to work out something you are happy with. Paraphrased heavily, the reprint says there is a 5% speed improvement overall, with up to 33% improvement (max.) for routines using the "fast video" firmware options. GW-Basic has a problem with displaying characters in the medium resolution graphics screen, and a hard disk diagnostic (test #4, seek time) doesn't work. There is also a set of problems with booting, but these are supposed to be fixed by the below modifications to the boot EPROM (though the article includes the expected YMMV-and-your-machine-may-explode kind of disclaimers). The EPROM is, for a Rainbow 100B or 100+, a 27128 PROM. If you install a V20, that EPROM (located between the connectors for the hard disk option) should be duplicated with the following changes: Location Data -------- ---- 072F 64 08E6 E8 08E7 17 08E8 36 08E9 90 0B36 20 3F00 51 3F01 B9 3F02 04 3F03 00 3F04 D4 3F05 0A 3F06 E2 3F07 FC 3F08 59 3F09 C3 3FFE EC 3FFF B2 For a PC100A, the Hard disk problem is irrelevant, the EPROM is a 2764, and the change list is: Location Data -------- ---- 043F 64 067D 20 1FFE 2B 1FFF 70 Let me know if you try it; I have not. Good luck! - Mark