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
File:TRS-80 Model 100.orig.bin
File:TRS-80 Model 100.y2k.bin
Most Model 100's have a non-standard pinout for the system rom socket.
If your original system rom has the part number LH535618 (most will), then you can use FlexROM_100 (optionally with REX Classic) to install the patched ROM.
If you have a late model without LH535618, then you can use a plain 27C256, or FlexROM_102 (optionally with REX Classic), or 28C256_to_27C256.
TANDY Model 102
- 0x5A53 0x31 -> 0x32
- 0x5A56 0x39 -> 0x30
File:TANDY Model 102.orig.bin
File:TANDY Model 102.y2k.bin
You can use a plain 27C256, or FlexROM_102 (optionally with REX Classic), or 28C256_to_27C256 to install the patched rom.
TANDY Model 200
Model 200 system rom spans 2 chips, 32k at M15, and 8k at M13. Only M15 needs to be modified.
- 0x6DF1 0x31 -> 0x32
- 0x6DF3 0x39 -> 0x30
File:TANDY Model 102.M15.orig.bin
File:TANDY Model 102.M15.y2k.bin
File:TANDY Model 102.M13.orig.bin (the 8k 2nd chip just for completeness)
You can use a plain 27C256, or 28C256_to_27C256 to install the patched rom.
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 a plain 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
You can use a plain 27C256, or 28C256_to_27C256 to install the patched rom.
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
File:NEC PC-8201A.orig.bin
File:NEC PC-8201A.y2k.bin
For PC-8201/PC8201A you can use a plain 27C256 or a 28C256_to_27C256 to install the patched rom.
File:NEC PC-8300.orig.bin
File:NEC PC-8300.y2k.bin
For PC-8300 you can use FLASH_23C1000 to install the patched rom.
References
http://www.muppetlabs.com/~chris/model100/y2000.html
https://www.web8201.net/default.asp?content=NECY2K.asp