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 39
Replace 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

US

0x5A53 0x31 -> 0x32

0x5A56 0x39 -> 0x30

File:TANDY Model 102.us.orig.bin
File:TANDY Model 102.us.y2k.bin

UK

0x5A53 0x31 -> 0x32

0x5A56 0x39 -> 0x30

File:TANDY Model 102.uk.orig.bin
File:TANDY Model 102.uk.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 200.M15.orig.bin
File:TANDY Model 200.M15.y2k.bin

File:TANDY Model 200.M13.orig.bin (the 8k 2nd rom chip is not modified, included here just for completeness)

You can use a plain 27C256, or 28C256_to_27C256, or FlexROM_200 (optionally with REX Classic) 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

Europe:

0x5774 0x31 -> 0x32

0x5779 0x39 -> 0x30

File:M10 System ROM EU.orig.bin
File:M10 System ROM EU.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

To change the "19" in "1983", it's the same rule for NEC as all the rest, but there is also a second place to change the "83".

0x5D91 0x31 -> 0x32

0x5D94 0x39 -> 0x30

0x7E30 0x33 -> 0x30

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