CPU
The Indigo came with two different CPU Boards, the IP12 and the IP20. Both uses a propietary VME based bus design to the Backplane, and have two GIO32 slots for expansion cards. The CPU Boards hold also the connectors for audio, serial, keyboard, mouse and AUI Ethernet.
IP12
The IP12 hardware design is the same as in the last Personal IRISes(
1
2
3
). It uses a MIPS R3000 Processor at 33 MHz. The processor is soldered on the CPU board, and therefore not upgradeable. It has 3 banks of each 4 proprietary 64 pin Simms, giving a memory from 8MB to 96MB (
1
2
3
). The memory Slots are labeled A1-A4, B1-B4, C1-C4.
IP20
The IP20 board is used only in the Indigo (
1
2
3
4
5
). The Indigo 2 and Indy using a similar board, the differences are only the expansion port (GIO64) and the backplane (EISA) as well as the form factor. The IP20 takes standard 72 pin PS/2 Simms with true parity. The Simms are labelled S1A-S4A, S1B-S4B and S1C-S4C. It can hold up to 384MB of memory. Since the Processor is on an own modules, it is upgradable. There are three different processor modules (PM). The standard configuration was the R4000 with 100MHz (PM1). Later SGI made an upgrade offer with a R4400/150MHz (PM2) (
1
2
3
). Some rare configurations used this PM at 100MHz, which was sold as instead of the R4000 CPU. The PROM hinv will always report the external speed of the processor (50 or 75 MHz), newer IRIX version the internal speed (100 or 150 MHz). The processor was manufactured by external companies, for example Toshiba (1) or NEC (1)
Benchmarks and technical data
Pictures