Category Archives: PC history

The Answer To 0x49: Fujitsu FMR

This is a guest post by A. N. Other. The following was originally intended as a comment to “Not MSX Either“, the 4th installment in the hunt for the mysterious 0x69 FAT VBR-start byte which was allowed in DOS. Due … Continue reading

Posted in DOS, NT, PC hardware, PC history, Undocumented | 7 Comments

Decoding Seagate Date Codes

More or less everyone knows that throughout the 1990s and 2000s, Seagate did not label their drives with a date of manufacture like everyone sane would do, but instead used a custom and somewhat mysterious/confusing “date code”. For reasons that … Continue reading

Posted in PC history, Seagate, Storage | Leave a comment

Those Lot Numbers are Old

The other day I was trying to decode the “lot numbers” printed on certain Seagate drives. In the meantime, I realized that those lot numbers have been in use for quite some time. They were in use around 2000, like … Continue reading

Posted in PC history, Seagate | 11 Comments

Not MSX, Either

Further examining the mystery of boot sectors supposedly starting with byte value 69h, I considered the possibility that the check could have been added for MSX machines. The MSX platform ticks a lot of boxes: It wasn’t 8086 (but rather … Continue reading

Posted in IBM, Microsoft, PC history | 15 Comments

Really Atari ST?

This blog has previously examined a very very strange code fragment in the BIOS module of DOS. To recap, when deciding whether a boot sector might have a valid BPB, DOS checks whether the first byte is a relative jump … Continue reading

Posted in DOS, Microsoft, PC history | 18 Comments

Breaking Into ASOS

The OS/2 Museum recently acquired a Quantum Bigfoot TS hard disk in mint condition. The Bigfoot drives, as some readers may remember, were rather oddball late-1990s 5.25″ IDE drives that were cheap, slow, and relatively big. There was a sticker … Continue reading

Posted in Compaq, PC history, SCO | 4 Comments

Well Hello

So after some furious disassembling, assembling, and linking, things got this far: It took longer than it ought to have because although IDA is great, I couldn’t figure out how to make it work with GW-BASIC’s bizarre segment usage. The … Continue reading

Posted in Compaq, Microsoft, PC history, Source code | 7 Comments

How Old Is OMF?

The Object Module Format (OMF), used by most DOS development tools, and eventually displaced by COFF/ELF in the 32-bit world, is quite old. It is a somewhat strange format because of its age, and it is quite complex, both because … Continue reading

Posted in Development, Intel, Microsoft, PC history, x86 | 8 Comments

GW-BASIC Source Notes

When I learned that Microsoft released the GW-BASIC source code, I was mildly curious to find out what is or isn’t there. The short answer is that there’s a whole lot, but a lot is also missing. Spelling note: Both … Continue reading

Posted in Microsoft, PC history, Source code | 18 Comments


Not long ago the OS/2 Museum acquired a boxed copy of the IBM PC LAN Program (PCLP) version 1.3 (1988) on 3.5″ floppies. The IBM PC Network Program (1985), later renamed to the IBM LAN Program, was IBM’s first PC … Continue reading

Posted in Archiving, IBM, Networking, PC history | 9 Comments