Readers have been wondering what kind of valuable warranty users of Microsoft’s Quick Pascal 1.0 (and other products) might be voiding by running it on top of DR DOS 3.3x or 3.40. I don’t have the original Quick Pascal 1.0 package, but I have a BASIC 6.0 package from 1988 which likely used identical wording. Here’s the scan:
In other words, the “valuable warranty” was a very limited 90-day warranty that actually promised next to nothing. In practice Microsoft might refuse to support DR DOS users, but those would probably have little difficulty showing that the same bug occurs when running on top of MS-DOS.
I also found the following fascinating exchange from almost two years after the check was first implemented:
From tomle Wed Jan 10 17:50:11 1990 To: billg russw Cc: markche Subject: Re: what can we do about this? Date: Wed Jan 10 17:46:21 1990 We had to really stretch to get this mechanism to work at all. We dug deeply into the bowels of Dos to be sure it was a "real Dos". We warned at the time that this is a dangerous thing to do. It will be very easy for us to break our own apps with this mechanism. I think it's a bad idea and with Gordon looking at drastically altering the kernel the chance of breaking ourselves is even higher. We should stop this activity now. It's dangerous and, in the end, I think we'll only hurt ourselves. Tom | >From russw Wed Jan 10 17:16:05 1990 | To: tomle | Subject: what can we do about this? | | ie. to change the detection mechanism | | From markche Wed Jan 10 11:37:04 1990 | To: billg | Subject: Alien DOS Check | Cc: billp markche philba russw steveb | Date: Wed Jan 10 11:35:29 1990 | | This has been implemented in the following ms products: | | QP 1.0 | QASM 2.01 | Fortran 5.0 | BASIC PDS 7.0 | Works 2.0 (in setup) | Flight Sim 4.0 | | The alien DOS check does not detect the most recent | version of DR DOS (3.41); it does detect versions | prior to this.
As readers have pointed out, the fears that Microsoft would “break” its own products were well founded, and exactly that happened with NTVDM. Fortunately the check was bogus from the start and the products actually worked on top of NTVDM just fine.
The references to “Gordon” were about Gordon Letwin improving core DOS in an attempt to thwart DRI. It appears that very little or nothing came of it since the DOS 5.0 (and DOS 6.0) core was not substantially different from DOS 3.4/4.0. Microsoft may well have found out that the only way to keep 100% compatibility was to make minimal changes.