Click here or click onto the photo for a full size version of this picture. As an afterthought to the SLC series of enhanced 386SX machines, IBM built a version with a clock-tripling processor, i.e. a CPU that runs at 75 MHz internally, yet keeps the external clock of 25 MHz. I call this an 'afterthought' because the speed gain is extremely limited: the 16K cache in the CPU still runs at 25 MHz, which means that only the CPU operation itself is accelerated by 50%. Most of the time, the CPU core is probably waiting faster to get its code to execute from the cache or memory. A symtom is that the Linux 'BogoMips' value (a value commonly misinterpreted as a benchmark) only improves from ~18 to ~21, which is far less than the clock ratio, and the speed improvement for real-world applications like compiling with gcc is almost zero :-( Click here or click onto the photo for a full size version of this picture. The back side, like all other parts of the SLC3, is exactly identical to the SLC2; one can see that this machine never had many expansion cards in it: most slots are still covered with break-out plastic pieces that you can remove once and never put them back again... Click here or click onto the photo for a full size version of this picture. Fortunately, this machine came with the additional drive holder for an internal 3,5 inch SCSI disk drive; this leaves the space below the floppy drive free for a CD-ROM or an additional hard drive (as in this case). Click here or click onto the photo for a full size version of this picture. A closer look onto the CPU reveals that there isn't really an SLC3 processor on the planar; it is a DLC3, i.e. a processor with a 386DX-style pinout and a bus with of 32 bits. Limiting it to 16 bits is no problem since the CPU has a pin called /BS16 that would even allow to switch the bus width on a per-cycle basis. Crippling it to 16 bits is of course another reason why there is virtually no performance improvement from the SLC2...

Processor: IBM 486SLC3 @ 75 MHz Coprocessor: Cyrix 83S87 @ 25 MHz Cache: 16K internally in CPU Memory: 16 Mbytes (options range from 4M to 16M) Bus: 3 MCA slots (16 bit) Interfaces (onboard): Mouse, Keyboard 2 x Serial 1 x Parallel Floppy (2.88M), allows attachment of up to 3(!) drives SCSI (narrow) XGA-2 Add-on cards: none Operating System(s): Caldera OpenDOS 7.01 Linux 2.2 (Slackware-based) Useful Links: Original Announcement from IBM Reference Diskette Diagnostic Diskette

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