Here is a first pass at the Miata hardware description I promised 
a while ago.  Sorry it took so long.

Currently, there is pretty good info out on:
  http://www.compaq.com/products/workstations/dig-glance.html

I started with the description for another machine and did a lot 
of editing.  I hope somebody will double check this. 

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Personal Workstation (Miata) 600a, 600au (and other speeds)

CPU-specific support for Personal Workstation was written by Andrew Gallatin. 

Supported Hardware

The Personal Workstations are Digital's PCI-based workstations in 
small deskside boxes.  They use the 21164 EV5 and EV56 versions of 
the Alpha.

The a versions come with IDE disks for running NT.  The au versions 
come with SCSI disks for running Unix and VMS.

There are 2 generations of the motherboard.  The first one had separate 
versions for the a vs au systems.  The second generation (Miata-GL) 
uses the same board on both systems. 

The Miata-GL uses the EV56 chip with byte/word instructions.  Earlier 
versions used the EV5 chips.  This description is for the Miata-GL.

The 600au model includes the following hardware: 

     DECchip 21164(A)/EV56 CPU (with BWE)
     DECchip 2117x Core Logic Chipset (Pyxis)
       It uses SDRAM simms.
     DECchip 21043-based PCI Ethernet - UTP 
     21154 PCI-PCI Bridge
     2 64 bit PCI slots (only some devices work - see bugs below)
     3 32 bit PCI slots behind the bridge
     3 ISA slots shared with the 32 bit PCI slots
     Qlogic ISP 1040B Ultra(20MHz)/Wide SCSI controller
       Packaged au systems normally include a SCSI disk.
     Contaq Microsystems 82C693 PCI-ISA Bridge and IDE+USB controllers
       Packaged a systems normally include an IDE disk.
     ATAPI CDROM drive
     Floppy disk controller with one 1.44MB floppy disk drive
     Two NS16550 UARTs 
     PS/2-style keyboard and mouse 
     Parallel Port 
     Windows Sound System compatible sound hardware 
     MC146818-compatible battery-backed clock and timer 

NetBSD/alpha supports all of the standard system hardware listed above. 

NetBSD/alpha also supports other PCI and ISA devices on Personal 
Workstations, as described on the PCI and ISA hardware support pages. 

Known Hardware-specific Bugs

The following are the known bugs in NetBSD/alpha's support of the 
Personal Workstation:

     PCI DMA reads that cross a page boundary don't work right.  
     This is not a problem for the 32 bit slots because PCI-PCI bridge 
     breaks transfers at a convenient place.  The firmware knows 
     about some PCI devices that work OK.  It refuses to enable other 
     devices if they are in a 64 bit slot. 

     32bpp frame buffers (e.g. the ZLXp-E2 and ZLXp-E3) are not currently supported.