The following string of hex code, when saved as a binary file, named
with the extension .COM, and run on some pentiums, will cause a hardware
error within the chip. The chip must be reset in order to recover. What this means in simple terms is that the computer will crash and you will have to either push the
'reset' button, or power down and restart your PC. This is reputed to
also work in a DOS window inside LINUX.
This problem can occur due to an error in the following Intel processors:
- Pentium processor
- Pentium processor with MMX technology
- Pentium OverDrive processor
- Pentium OverDrive processors with MMX technology
NOTE: This problem cannot occur on the following Intel processors:
- Pentium Pro processor
- Pentium II processor
- i486 and earlier processors
This problem is known as "Invalid Operand with Locked CMPXCHG8B
Instruction" and is erratum 81 on the Pentium processor errata list. For
more information, please contact Intel or go to the following Intel web
The HEX code:
We assume no responsibility. Study with care!
As a convenience, we have provided the file as a MS-DOS .com file right here on this server.
You can download 4bytes.com.
If you choose to download this file, be sure that your browser does not, in the usual idiotically jovial drooling stupor experienced by browsers, proceed to run the file, or your pentium may crash. This cpu-identification tool is not a toy, and we aren't responsible for what you do. legal
Download a useful dos-based hex editor and do it yourself!