Editing SGI Visual Workstation (section)

==Computer architecture==
There are two series of the Visual Workstations. All are based on Intel processors; the first series (320 and 540) used SGI's ARCloader PROM and Cobalt video chipset, the remainder are essentially standard PCs.

The 320 and 540 use a [[Unified Memory Architecture|Unified Memory Architecture (UMA)]] memory system. This shares the video and system memory and runs them at the same speed, and allows for up to 80 percent of the system ram to be applied to video memory. The allocation is static, however, and is adjusted via a profile.<ref>{{cite web|url=http://www.dccmag.com/1999/08/06/sgi-320-nt-workstation-includes-striking-differences/|title=SGI 320 NT Workstation Includes Striking Differences|last=Bolkan|first=J.V.|date=6 August 1999|website=DCC Mag|accessdate=5 August 2019}}</ref> The 320 and 540 also use the onboard Cobalt video adapter, which is SGI's proprietary graphics chipset. The firmware used in these systems is a PROM that enables booting into a graphical subsystem before the OS was loaded. In this regard they resemble the Irix/MIPS line of SGI computers such as the [[SGI O2]].
 
The 320 and 540 also stand out for having FireWire ([[IEEE 1394]]) ports, onboard composite/[[S-video]] capture, and USB keyboards and mice. They differ from each other in that the 320 is dual Pentium II/III-capable with 1GB maximum system RAM, while the 540 is quad Pentium III Xeon-capable with 2GB maximum system RAM.<ref name=vw540_man_it>{{cite web
| title = Silicon Graphics 540™ Visual Workstation Manuale dell'utente
| lang  = it
| url   = https://archive.org/details/manualzilla-id-6152636/page/166/mode/1up
| publisher = Silicon Graphics
| date  = 1999
}}</ref>  Both computers use a proprietary DIMM module that is essentially the same as ECC SDRAM PC-100, but in a package one-half normal size. The maximum memory per module is 96MB, and the SGI 320 has twelve memory slots. The FireWire ports that are built into the 320 never functioned. SGI distributed Orange Micro FireWire cards about a year after production commenced, in lieu of fixing the FireWire ports.

Both the 320 and 540 are further limited by having PCI slots (albeit two 66&nbsp;MHz and one 33&nbsp;MHz slot) that operated at 3.3V,<ref name=ntmagau_1999_11>{{cite magazine
| url      = https://archive.org/details/windows_nt_australia_magazine-1999_11/page/n23/mode/1up
| date     = November 1999
| magazine = Windows NT Australia
| page     = 24-25
| title    = Silicon Graphics 320
| issue    = 10
| first    = Bill
| last     = O'Brien
}}</ref> out of step with the 5v slots used by most manufacturers. This limits the number of accessories that can be added.

The other Visual Workstations are built to compete with the new Intel processor based workstations that are considerably cheaper than SGI's line of MIPS workstations. They are little more than standard PCs, and use many parts that are also available in the aftermarket.