the Centris models that briefly existed during 1993: The 610, the 650 and the 660AV. Centris was a "mid-range" line of systems between the Quadra on the high end and the LC on the low end, but it was later decided that there were too many product lines and the name was dropped. Some machines of this era including the Quadra 605 were also sold as Performas. The last use of the name was for the Quadra 630, which was a variation of the LC 630 using a "full" Motorola 68040 instead of the LC's 68LC040, and introduced together with it in 1994. The 630 was the first Mac to use an IDE based drive bus for the internal hard disk drive, whereas all earlier models had used SCSI. The first three Apple Workgroup Server models, the WGS 60, the WGS 80 and the WGS 95 (mostly called "AWS 95" for "Apple Workgroup Server") were based on the Centris 610, the Quadra 800 and the Quadra 950, respectively. Processor The transition to the Motorola 68040 was not as smooth as the previous transitions to the Motorola 68020 or Motorola 68030. Due to the Motorola 68040's split instruction and data caches, the Quadra had compatibility problems with self-modifying code (including relocating code, which was common under the Macintosh memory model). Apple partially fixed this by having the basic Mac OS memory copy call flush the caches. This solved the vast majority of stability problems, but negated much of the Motorola 68040's performance improvements. Apple also introduced a variant of the memory copy call that did not flush the cache. The new trap was defined in such a way that calling it on an older version of Mac OS would simply call the previous memory copy routine. The net effect of this was that many complex applications were initially slow or prone to crashing on the 68040, although developers quickly adapted to the new architecture by relying on Apple's memory copy routines rather than their own (or flushing the cache), and using the memory copy that did not flush the cache when appropriate (most of the time). Specifications of Macintosh Quadras All Obsolete Timelines See also List of Macintosh models grouped by CPU type Timeline of Macintosh models References External links EveryMac.com - Macintosh Quadra series Lowendmac.com - Centris/Quadra Index Computer-related introductions in 1991