Also released in 1984 was the microprocessor version of the VAX know as the MicroVAX. There were many models of the MicroVAX but here I will concentrate on mostly five which include the two most commonly emulated and three others of historical and technical interest. The original model was the MicroVAX I which was essentially a slightly smaller microprocessor-driven version of the VAX-11/730 that supported up to 4 Megabytes of RAM. The MicroVAX I could only run MicroVMS where the II and 2000 could also run VAX/VMS and OpenVMS. All other MIcroVAX can only run OpenVMS. (Although they could technically run VMS 5.x, it cannot be emulated due to licensing issues.) It should be noted that none of the MicroVAXen supported PDP-11 compatibility. The next model was the MicroVAX II which was quite a jump in performance. It speed was comparable to the VAX-11/780, included a floating point processor, and supported up to 16 Megabytes of RAM. This is is my favorite relatively early VAX model to emulate and many of my tutorials will be based on it. The next Model is the MicroVAX 2000, a desktop sized MicroVAX. Processor-wise, it is identical to the MicroVAX II but feature-wise it is definitely a cost reduced version. It has no external bus and it supports only one floppy drive, one tape drive and up to two hard drives ranging in size from 20 to 156 Megabytes where the MicroVAX II to can theoretically support up to a combination sixteen floppy or 1.5 Gigabyte hard drives and 4 tape drives. Also, the MicroVAX 2000 supports up to 14 Megabytes RAM. The next model model line of the MicroVAX emulated here is the MicroVAX 3100 line. Three models of the MicroVAX 3100 are emulated but since they are so similar we will only concentrate on the highest-end of the three, the Model 80. These are much higher performance than the VAXstation II but uses SCSI for it’s storage controller instead of Massbus like on the on the VAX-11 and VAX 8000 or Q-Bus like on most other MicroVAXen. This allows a combination of up to 6 floppy, tape, and hard disk drives. The Model 80 also supports up 72 Megabytes of RAM. Even though the MicroVAX 3100 is much more powerful than the MicroVAX II, I find the more difficult to configure and also the maximum allowed size for hard drives is much smaller. I will save the best for last, the MicroVAX 3900. It is powerful, supports up to 64 Megabytes of RAM, like the MicroVAX II, it uses the Q-Bus with the sixteen hardrives and 4 tape drives that it allows. For later operating systems, this is always my choice. It’s only drawback, is that there is no VAXstation equivalent (Technically, Simh allows for emulation of a fictional VAXstation 3900, but I have never got it to work right.). There are many resources on the web for emulating the the MicroVAX 3900 so I will mostly provide only links and not in-depth tutorials.