Vendor-specific SCSI commands reference

Lately, I’ve been exploring the source of CacheX, a cache exploring tool created by one of MyCE members, spath. You can see the original thread here.

Ultimately, the objective is to rewrite the code for Linux, since I haven’t seen any tool available for this OS that would offer similar functionality. I’ve already got some very basic commands working. However, most of the stuff contained in this program is very new to me since I haven’t tackled with SCSI commands and stuff like this before.

I’ve been able to find information about the basic SCSI commands in Seagate’s official SCSI guide and the Multi-Media Commands reference. However, there are still some commands in the original CacheX source that remain cryptic to me. They are :

All of these commands are used as read commands. While the source is obviously enough to figure out how to use them, I would certainly like to find out more about them. Google did not help me at all, and I can only speculate that they are Plextor-exclusive commands. However, the source for qpxscan refers to 0xD4 and 0xD5 as “PLEXTOR_GET_AUTH”. 0xD8 is not even mentioned at all in that program.

While I do realize that most (if not all) information about vendor-specific commands is protected by burn-before-you-read NDAs, but even confirming this would be welcome.

Thank you in advance,


I wouldn’t worry about 0xD4 and 0xD5 (if my memory is not too bad) seems only the defunct Teac supported them with their super old drives.

The 0xD8 command is originally a proposal of Pioneer in their SCSI-2 command spec:

Plextor applied the 0xD8 command to their Sanyo based chipset drive firmware (non rebranded drives).

I forgot to mention that there are a few bugs in the CacheX program, some of them are mentioned by others in the original thread but spath didn’t really fix.

I have written my own version that is bug free and works on more drives properly. If people are still interested in such a tool I am willing to provide the tool.