Model T Y2K
"Model T computer" system rom Y2K patches
General
All the KC-85 clones have the same routine holding the century digits, though appearing at different addresses in different system roms.
A Y2K patching rule that applies the same to all machines is to just search for a certain string of bytes wherever it happens to appear, and edit.
Using the hex-editor of your choice:
Search for this sequence: 23 36 31 23 36 39Replace it with this: 23 36 32 23 36 30
TRS-80 Model 100
- 0x5A53 0x31 -> 0x32
- 0x5A56 0x39 -> 0x30
You can use FlexROM_100 and/or REX Classic to install the patched ROM.
Most Model 100's have a non-standard pinout for the system rom socket, so you need FlexROM_100 or something like it in order to replace it with a standard chip.
Olivetti M10
North America:
- 0x5A5B 0x31 -> 0x32
- 0x5A5E 0x39 -> 0x30
File:M10 System ROM NorthAmerica.orig.bin
File:M10 System ROM NorthAmerica.y2k.bin
You can use an ordinary 27C256 UV Eprom, or one-time-programmable 27C256, or 28C256_to_27C256 to install the patched rom.
Kyotronic KC-85
- 0x575E 0x31 -> 0x32
- 0x5761 0x39 -> 0x30
File:KC-85.orig.bin
File:KC-85.y2k.bin
NEC PC-8201A, PC-8300
NEC has a second place that must be edited in addition to the same rule as all the rest.
- 0x5D91 0x31 -> 0x32
- 0x5D94 0x39 -> 0x30
- 0x7E30 0x33 -> 0x31
- 0x7E31 0x38 -> 0x30
For PC-8201/PC8201A you can use a plain 27C256 or a 28C256_to_27C256 to install the patched rom.
For PC-8300 you can use FlashROM_8300 to install the patched rom.
References
http://www.muppetlabs.com/~chris/model100/y2000.html
https://www.web8201.net/default.asp?content=NECY2K.asp