The PROM is the hardware device where the boot firmware for MIPS SGI machines is stored. This firmware will be retrieved and stored in memory at a specific location. After the memory controller on the mainboard has initialized the MIPS-processor and peripherals on powerup, the processor will jump to the memory location of the stored PROM image and starts the firmware.
In machines manufactured earlier than ~1996 it consists of a PROM (Programmable ROM) or EPROM (Erasable Programmable ROM). In order to support additional/newer processors, peripherals and memory sizes the PROM had to be updated by exchanging it physically. Later machines like the O2, Origin 200, Octane and Onyx2 carried EEPROM's (Electrically Erasable Programmable ROM) to store the firmware, so that it can be updated from IRIX.
SGI Indigo R3000 PROM
The Indigo R3000 PROM is a Am27C2048 2Mbit 40 pin EPROM located in the center of the mainboard under the GIO expansion bracket.
|SGI Part#||IP12 PROM version string||Added HW support and fixes|
|070-8054-002||SGI Version 4.0 Rev A HP1, Jul 18, 1991|
|SGI Version 4.0.1 Rev C LG1/GR2, Jul 9, 1992||GR2 XZ/Elan graphics|
|070-8088-002||SGI Version 4.0.1 Rev D LG1/GR2, Mar 24, 1992|
SGI Indigo R4000 PROM
The Indigo R4000 PROM is a 40 pin M27C4002 4Mbit EPROM located in the center of the board under the GIO32 expansion bracket.
|SGI Part#||IP20 PROM version string||Added HW support and fixes|
|070-8116-004||SGI Version 4.0.5D Rev A IP20, Aug 19, 1992|
|070-8116-005||SGI Version 4.0.5G Rev B IP20, Nov 10, 1992 (BE)|
SGI Indy/Challenge S PROM
The Indy/Challenge S PROM is like the Indigo R4K a 40 pin M27C4002 4Mbit EPROM and is located under the graphics board or in case of the Challenge S, the IO4Plus.
|SGI Part#||IP24 PROM version string||Added HW support and fixes|
|070-9101-004||SGI Version 5.1 Rev B3 IP24 Sep 17, 1993 (BE)|
|070-9101-005||SGI Version 5.1.2 Rev B4 R4X00 IP24 Dec 9, 1993 (RE)|
|SGI Version 5.0 Rev B5 IP24 Jun 20, 1994 (BE)||GR3-XZ graphics|
|SGI Version 5.0 Rev B5 IP24 Jul 15, 1994 (BE)||Presenter|
|070-9101-007||SGI Version 5.0 Rev B6 IP24 Sep 28, 1994||R4600PC/133 and R4400SC/200|
|070-9101-008||SGI Version 5.3 Rev B7 R4X00 IP24 Feb 16, 1995 (BE)|
|070-9101-011||SGI Version 5.3 Rev B10 R4X00/R5000 IP24 Feb 12, 1996 (BE)||R5000|
SGI Indigo2/Challenge M PROM
The Indigo2/Challenge M PROM is a 40 pin M27C4002 4Mbit EPROM just like the Indy and Indigo R4K and is located in the GIO64/EISA Interface compartment close to the fan. For the Power Indigo2 (IP26) and the Indigo2 R10000 (IP28) The PROM's are different, but the location of the PROM is the same
|SGI Part#||IP22 PROM version string||Added HW support and fixes|
|070-8127-002||SGI Version 5.1 Rev B IP22 Sep 16, 1993 (BE)||R4400SC/150|
|070-1367-004||SGI Version 5.3 Rev C IP22 Oct 20, 1994 (BE)|
|070-1367-011||SGI Version 5.3 Rev E IP22 Sep 28, 1995||R4400SC/250 and High/Max IMPACT gfx|
|070-1367-012||SGI Version 5.3 Rev E IP22 Jan 29, 1996||Presenter and Solid IMPACT gfx|
|IP26 PROM version string|
|070-1371-003||SGI Version 6.0.1 Rev A IP26 Dec 9, 1994|
|070-1371-004||SGI Version 6.0.1 Rev A IP26 Dec 23, 1994|
|IP28 PROM version string|
|070-1477-001||SGI Version 6.2 Rev A IP28 Jun 10, 1996|
|070-1477-002||SGI Version 6.2 Rev A IP28 Aug 26,1996|