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IBM PS/2 Model 95 (Type 2 Complex)

Photo of IBM PS/2 Model 95
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Another example from the many variants of IBM's Model 95, in this case with the so-called 'Type 2' processor complex. The diagnostic display next to the power switch clearly identifies it as a Model 95...

The full designation of this machine is 9595-ALF. 95xx models from the PS/2 line are the newer ones with better video, more on-board serial/parallel ports, or better SCSI. This is however not true for the 'smaller' 9595 models: They do not have the redesigned planar present in the the Server 95(A) family, they are slightly brushed-up 8595 models. Similarly to the 8590-->9590 transition, they simply received a video card capable of doing graphics at eye-friendly refresh rates and a 2.88M floppy drive (not that important these days any more...). The basic chassis remained the same, as can be seen by the missing hard drive access LED (the 95's with the new planar do have an additional second LED for hard disk accesses).

Photo of IBM PS/2 Model 95's innards
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Summing up, the PS/2 95 can hold up to 7 drives: The topmost is almost always occupied with a floppy drive and not designed for 5,25-inch devices: there are no side rails, only bottom rails for the plastic sockets 3,5 inch devices are screwed on. A second bay below has similar capabilities and may be used for a second floppy or similar 3,5-inch devices. The third bay has side rails for 5,25-inch devices and is the perfect slot for a QIC streamer, CDROM drive or other half-height devices. Each of the two bottommost bays offers space for 5,25-inch full height devices. If you have some old 'large' SCSI disks (the ones you should not drop on your feet!), here is the perfect place to deposit them! Of course, you may also put two HH drives into each bay; the upper rail pair for this purpose is removeable.

Photo of IBM PS/2 Model 95's RAM bank
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The RAM modules are located at the bottom of the planar, hidden by the power supply during operation. Removal of the power supply is the usual mechanism of loosening the large blue screw and swinging the power supply block out (don't forget to unconnect the power supply cord before...). The system may take up to 8 72-pin modules whose type and maximum size depends on the used processor complex; in the case of the Type 2 complex, up to 8x 8Mbyte true parity modules may be used.

Photo of IBM PS/2 Model 95's CPU Card
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One could say the Type 2 processor complex is an example of minimalism; compared to its Type 1 predecessor and later successors, the board looks almost empty. It has offered in two variants: With a 486SX25 CPU and a socket for a DX2/50 overdrive (models -xHx), or directly with a 486DX2/50 CPU ((models -xLx). In the latter case (like here), the socket for the overdrive CPU is unnecessary and not present, making the board look even more empty. Though the whole design might look primitive (no L2 cache!), it was the result of extensive simulations at IBM what is actually needed to run a file server. The result at that time was that this configuration is enough to saturate 16Mbps Token Ring, therefore more CPU would have been a waste. Of course these days, one expects a server also to run a GUI and other compute-intensive jobs at the same time, so this estimation is not true any more...

Photo of IBM PS/2 Model 95's Graphics Board
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The XGA-2 graphics adapter was the first IBM graphics adaptor capable of displaying high-resolution graphics at acceptable refresh rates and is the reason for the blue IBM badge at the front :-) The 1 Mbyte of VRAM is not extendible, therefore one is limited to 1024x768 @ 8bpp or 800x600 @ 16bpp. This is however still much better than the short SVGA Adapter/A found in many 95's, which has only half a megabyte, is badly documented and not supported by Linux.

Photo of IBM PS/2 Model 95's SCSI Controller
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The SCSI-Controller is the so-called 'Spock', a busmaster adapter with 512K or 2 Mbytes of local RAM for caching purposes. Most of the time, it was only equipped with half a megabyte, but it is easy to extend them once you figure out how to modify standard SIMMs to the IBM pinout (see here for further information).

Intel i486DX2 @ 50 MHz
integrated into CPU
8K internally in CPU
32 Mbytes (options range from 8M to 64M)
8 MCA slots (32 bit)
Interfaces (onboard):
  • Mouse, Keyboard
  • 1 x Serial
  • 1 x Parallel
  • Floppy (2.88M), allows attachment of up to 3(!) drives
Add-on cards:
  • IBM 16/4 Token Ring Adapter
  • IBM XGA-2 Graphics Adapter
  • IBM SCSI Controller with Cache(2M)
  • Operating System(s):
    • Caldera OpenDOS 7.01
    • Linux 2.2 (Slackware-based)
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    ©2000 Alfred Arnold,