The Jensen is an EISA system with a 150 MHz 21064. The DECpc AXP 150 and DEC 2000 AXP differ only in their bundled software. ¹⁾ The DEC 2000 Model 500 was code-named Culzean. ²⁾

• 21064 at 150 MHz ³⁾, given in Digital's specification table as the "DECchip 21064 (EV4 P2 or P3)"; 1 MiB of boot and diagnostic firmware ROM; 16 MiB of DRAM expandable to 128 MiB ⁴⁾
• EISA only: it was the only Alpha platform in the kernel without PCI ⁵⁾, and apart from a few VME OEM boards the only Alpha system Digital built without PCI ⁶⁾
• No dense memory space, only sparse ⁷⁾
• The real-time clock is a PC part at a non-standard address, one of several unusual features of the Jensen I/O subsystem ⁸⁾
• Memory goes in eight connectors on the system module, grouped in two banks. A memory option consists of four memory modules, every connector in a bank must be filled, the two module types must not be mixed within a bank, and bank 0 must always hold an option. The only options were 16 MiB and 64 MiB, and the DEC 2000 Model 300 AXP required at least 32 MiB. ⁹⁾ See Conflicting information.
• The deskside DECpc AXP 150 and DEC 2000 Model 300 have one keyboard port, one mouse port, two serial ports, one parallel port, and six EISA connectors; the pedestal DEC 2000 Model 500 has one serial port and no keyboard or mouse port in its specification table, the same six EISA slots, and weighs 54 kg against the 21 kg of the deskside box. ^{10) 11)}
• SCSI bus letters follow EISA slot order, with bus letter A assigned to the SCSI adapter in the lowest-numbered EISA slot, and the console's SET SCSI_{A | B} command sets each adapter's host ID. ¹²⁾

Which console the machine runs is held in the OS_TYPE environment variable, whose values are VMS, OSF, and NT, and which can be changed from either console. A second variable, AUTO_ACTION, sets the power-up action (RESTART, HALT, or BOOT) and applies only to OpenVMS and OSF/1. ¹³⁾ Linux needs the OSF console. ¹⁴⁾

From SRM, SET OS_TYPE NT followed by Ctrl+P or the halt button brings up the ARC "Boot menu", which identifies itself as "ARC Multiboot DEC Version n.nn". ¹⁵⁾ Going back is a menu walk rather than a command: Supplementary menu, Set up the system, "Switch to OpenVMS or OSF console", then the reboot selection menu, and finally a full power cycle with a 15 second wait. ¹⁶⁾

There are separate EISA Configuration Utilities for Windows NT and for OpenVMS and OSF/1. ¹⁷⁾

Linux 6.9 was the last version to support the Jensen, with CONFIG_ALPHA_JENSEN; Linux 6.10 removed support for processors older than the EV56 (21164A). ¹⁸⁾ The Jensen needs its own kernel and cannot boot a generic kernel image. ¹⁹⁾

There is no MILO for the Jensen, so Linux runs under the OSF PALcode of the SRM console. The disk is prepared from the ARC console, which can read the floppy drive, and the kernel is then booted from SRM. ²⁰⁾ Early versions of aboot required firmware version 1.7 (see Conflicting information). ²¹⁾

The machine was developed by the group that designed the 21064, through the Beta and Theta demonstration systems, as a low-cost PC-style design whose base system deliberately contained little, leaving most capabilities to ISA and EISA option cards. ²²⁾ Olivetti sold a rebadged version as the R7-600. ²³⁾

The Jensen was the first machine to run Alpha/Linux, initially with a 32-bit kernel, followed by the Avanti (AlphaStation 400). ²⁴⁾

The following sources conflict with each other or with the account given above. They are listed here for further investigation.

• Jensen firmware needed for Linux
  • "VGA problems in a Jensen, was: Re: headless boot", Martin Ostermann, axp-list, 11 Dec 1996: "make sure you got v1.7 disks to switch back, because aboot doesn't work with later versions."
  • "Re: Installing linux on axp150", Sebastian Moeller, axp-list, 3 Jun 2000: "IIRC v1.7 is only required for the ELSA Winner 1000 ISA/EISA (twinbus)"
  • "RE: Downgrade firmware", H.C.vanderVegt@DTO.TUDelft.nl, axp-list, 20 Feb 2001: "the old aboot till 0.5 needs rom version 1.7 and the new aboot 0.7 supports the new roms (not official)"
• Memory modules per bank
  • "Alpha hardware", Jay Estabrook, axp-list, 5 Dec 2008: the Jensen and Noname "had only 64-bit mem bus, and thus required SIMMS in pairs, not quartets".
  • DECpc AXP 150 and DEC 2000 Model 300 AXP Customer Technical Information, pp. 12-6 to 12-7: "A memory option consists of four memory modules. When you install a memory option in a memory bank, you must install a memory module in all of the connectors in that bank."