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I found one of these when I was Autodesk back in the early 90s. It's been awhile, so I'm undoubtedly remembering something incorrectly. This was in the early
by msisk6 12y ago
I found one of these when I was Autodesk back in the early 90s.
It's been awhile, so I'm undoubtedly remembering something incorrectly.
This was in the early days of protected mode DOS software. Some customers were reporting an lockup issue with AutoCAD in rare instances when a particular command was used.
It took awhile, but I finally narrowed it down to running the "3-point arc" command on a system with a math co-processor and low memory (so it's paging) on certain 386-20 chips.
I don't recall the exact fix, but we did put some Intel-recommended code in the app to workaround the lockup. The 386 was quickly superseded by the 486 (which had its math co-processor built in which was huge for AutoCAD users back then) so this entire issue quickly disappeared.
Fun times.
- GFK_of_xmaspast 12y agoThe 486sx, at least at the start, did not have a coprocessor at all.
- marssaxman 12y agoThe 486DX was the original 486 and it definitely did include an FPU. The FPU-free 486SX came along a couple of years later. My recollection is that the SX was originally a way to make use of 486DX chips that failed manufacturing tests on the FPU; they'd disconnect the FPU portion of the die and sell the busted chips as "486SX". Same trick AMD pulled with the 3-core Phenom.
- GFK_of_xmaspast 12y agoThe 486dx did, which is why I specified 486sx.
- marssaxman 12y agoMy apologies; I thought you were making a comment which was intended to be relevant to the one you were replying to, which concerned the change from the 386 to 486DX. I am not sure what relevance the configuration of the later 486SX would have to the situation msisk6 described.
- yuhong 12y agoRapidCAD was a 486 in a 386 socket which was specifically designed for CAD.