There is a lot of confusion over what DASDDRVR.SYS is, what it is used for, which PS/2 models require it, and what exactly it fixes.  (July 1991 version is 3,068 bytes)

The following should dispel the mystery surrounding DASDDRVR.SYS.

Model 85, 90, and 95 Systems Don't Need DASDDRVR
   DASDDRVR functions are performed by updated Reference / Diagnostics diskettes, EPROM updates [T1 and T2], and/or Flash updates.

What is it? 
   DASDDRVR.SYS (Direct Access Storage Device Driver) is a set of software patches that fix various BIOS bugs common to several PS/2 models.  A common misconception is that DASDDRVR.SYS is a set of DOS patches; and additionally that it is not needed with DOS 4.0x or later; only V3.3.  Both statements are incorrect.

   IBM could have chosen to replace thousands of BIOS chips on PS/2 motherboards, yet went with the software approach.  Why? A program installs DASDDRVR.SYS on a PS/2 hard disk drive, and adds a statement to CONFIG.SYS.  Then when the system is booted, the BIOS patches overwrite the BIOS code in memory (that was copied from the BIOS ROM chips).  Not only does this give IBM and the user the flexibility of later replacing DASDDRVR.SYS with a newer version containing additional BIOS patches, if necessary; but it also eliminates the down time and inconvenience that would result from taking the system to an authorized servicer to have the BIOS ROM replaced. 

Who needs it? 
   Originally, a few BIOS bugs were found affecting several PS/2 models.  Two versions of DASDDRVR.SYS were written, one for MCA, and one for non-MCA PS/2s.  But as several more PS/2s were affected by these or newer bugs, both versions of DASDDRVR.SYS were merged into one.

   DOS 3.3 and later users with specific problems with a listed PS/2 should install DASDDRVR.SYS. The install program determines which fixes apply to that system.  PS/2 models not on the list do not need DASDDRVR.SYS, and will not benefit by installing it. 

Why isn't DASDDRVR.SYS required on OS/2 or AIX-based PS/2s?  
   Because these operating systems routinely replace hardware BIOS code in memory with customized software versions.  They already contain the fixes inherent in DASDDRVR.SYS. 

What problems does it fix?  [July 1991]
There are twelve fixes that affect the specific systems: 

Problems Systems Affected
1) Failures occur when reading some 720K program floppies. 8530-E01/E21; 8550-021; 8560-041/071; 8580-041/071
2) Intermittent "Not Ready" or "General failure" error messages when accessing diskettes. 8550-021; 8560-041/071; 8580-041/071
3) 3.5" floppy format failures when attempting to format multiple diskettes consecutively. 8550-021; 8560-041/071; 8580-041/071
4) Combined 301 / 8502 errors at power on, or after power interruption. 8550-021; 8560-041/071
5) System clock loses time (8550), or combined 162 and 163 errors during system POST (8560). 8550-021; 8560-041/071.
6) Unable to install Power-on Password program with DASDDRVR.SYS installed.  8550-021; 8560-041/071; 8580-041/071
7) Device attached to COM2, COM3, or COM4  not detected. 8530-E01/E21
8) Devices that use interrupt request level 2 (IRQ2) fail. 8530-E01/E21
9) 3.5" floppy format failures when attempting to format >1 floppy.  8570-Axx (all); 8580-Axx (all)
10) System performance degradation from processor-intensive devices.  8550-021/031/061; 8555-031/061; 8560-041/071
11) Error in microcode routine that enhances long-term reliability of 60/120MB disk drives. 8550-061; 8555-061; 8570-061/121/A61/A21; 8573-061/121
12) Time & date errors occur when resetting time & date. Intermittent date changes can occur when system is restarted by pressing C-A-D  8530 (all)

How do I get and install it?

Most versions of various MCA PS/2 RefDisks contain some version of DASDDRVR.SYS. (Non-Micro Channel PS/2 Model 30 286 provides DASDDRVR.SYS on the Setup Diskette) But several versions of DASDDRVR.SYS have been released, with different numbers of fixes, so it is important to get the latest possible version of the appropriate RefDisk. Depending on the diskette version, there may be additional fixes in a later version.

If you have the latest Reference Diskette, use it. If not, you may look for the PS/2 System Update Diskette (P/N 04G3288. This diskette contains a version of DASDDRVR.SYS, but it is possible that by the time you read this and order it, a newer version may have been released on a new Reference Diskette. Still, a fairly recent version is better than an older one you may have on the Reference Diskette that came with the system. If DASDDRVR.SYS is already installed on a system, but you don't know whether it is the latest, just look at the file size. The current version (as of July 1991) is 3,068 bytes).

Installation is a snap. Simply insert the diskette in the A: drive, and type: A:INSTALL from the C> prompt. That's all there is to it!

The install program copies the DASDDRVR.SYS file to the hard disk drive, and updates CONFIG.SYS to use it. After rebooting the system you are done.

One final note: This driver may be ordered and installed by anyone. It includes instructions, and does not require dealer intervention.

Content created and/or collected by:
Louis F. Ohland, Peter H. Wendt, David L. Beem, William R. Walsh, Tatsuo Sunagawa, Tomáš Slavotínek, Jim Shorney, Tim N. Clarke, Kevin Bowling, and many others.

Ardent Tool of Capitalism is maintained by Tomáš Slavotínek.
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