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The AlphaServer 2100 is a symmetric multiprocessing PCI/EISA server supporting up to four CPUs, and the AlphaServer 2000 (Demi-Sable) is a two CPU version of it. ¹⁾ Digital sold them from 1994 with 21064 and 21064A CPUs (4/xxx models), then 21164 CPUs (5/250 and 5/300) and finally the 21164A (5/375). ^{2) 3) 4)}

Except where noted, the following comes from the technical summary. ⁵⁾

• Up to four CPU modules on the AlphaServer 2100 and two on the AlphaServer 2000, in a shared set of system bus slots with the memory modules; slot CPU0 must be filled
• 275 MHz 21064A with 1 MiB of backup cache on the 4/275 models, 21164 at 250 or 291 MHz on the 5/250 and 5/300 models (KN470 and KN480 modules), and 21164A at 375 MHz on the 5/375 models (KN490 module) ⁶⁾; CPU modules carry 8 KiB of serial ROM, a power-up diagnostic microprocessor, the system bus arbiter, and 1 or 4 MiB of direct-mapped backup cache. Systems equipped with EV5 CPUs are called Gamma. ⁷⁾
• 128-bit multiplexed address and data system bus with central arbitration, longword parity, 32-byte transfers, and 666 MB/s peak bandwidth
• AlphaServer 2100: up to four memory modules, 2 GiB total, in 64, 128, and 512 MiB modules, interleaved two or four ways
• AlphaServer 2000: up to two memory modules, 1 GiB total, built from 4 MiB (1M x 36) or 16 MiB (4M x 36) 70 ns 72-pin SIMMs, four banks per module, interleaved two ways
• 256-bit interface to the DRAMs, ECC and address parity, read stream and write transaction buffers
• Three 33 MHz 32-bit PCI slots on both systems
• Eight 8.33 MHz EISA slots on the AlphaServer 2100 and seven on the AlphaServer 2000, all bus master capable
• 21040 (Tulip) PCI Ethernet controller with AUI or twisted-pair, onboard on the AlphaServer 2100 and an adapter on the AlphaServer 2000 ⁸⁾
• PCI single-ended 8-bit Fast SCSI-2 controller; wide SCSI is supported through option controllers ⁹⁾
• 1 MiB of flash ROM, 8 KiB of NVRAM, TOY clock, two serial ports, bidirectional parallel port, floppy controller, PS/2 keyboard and mouse, PC-style speaker
• On the AlphaServer 2100 this I/O is on a separate standard I/O module; on the AlphaServer 2000 it is on the I/O backplane
• BA35E StorageWorks shelves holding up to eight 3.5-inch SCSI drives each, configurable as a single or dual bus
• Sold as pedestal, rackmount, and cabinet systems; a single cabinet could hold a three node, twelve CPU cluster. ¹⁰⁾
• CPU module types cannot be mixed: the KN450 (21064) and KN460 (21064A) modules cannot be used in the same system. ¹¹⁾
• CPUs of different speeds are not supported together. ¹²⁾

Use the final SRM version, V5.3 (see final SRM versions and Updating firmware).

Current kernels support only the Gamma systems with EV56 (21164A) CPUs, that is, 5/375 systems with KN490 modules (CONFIG_ALPHA_SABLE, or a generic kernel). They boot from the SRM console with aboot; there is no MILO for the Sable. ^{13) 14)} Linux 6.9 was the last version to support the 4/xxx models and the 5/250 and 5/300; Linux 6.10 removed support for processors older than the EV56 (21164A), along with the early EV4 Sable machine vector (sable_mv). ^{15) 16)}

The onboard SCSI controller is an NCR 53C810, ¹⁷⁾ which uses the sym53c8xx driver. ¹⁸⁾ The only current driver for the 21040 Ethernet controller is de2104x; the tulip driver handles later Tulip chips but not the 21040. ^{19) 20)} de2104x has been reported to fail with the onboard 21040 of the Multia; ²¹⁾ no report says whether it works with the AlphaServer 2100's. For a serial console, see Using SRM.

• SMP: untested on current kernels. The most recent report, from 2015, is that SMP on the Sable had not worked since about the Linux 2.2 era, on an AlphaServer 2100 with four 275 MHz CPUs; ²²⁾ a 2008 report also said that the AlphaServer 2100 ran uniprocessor kernels but crashed with SMP kernels. ²³⁾
• Weight and power: the AlphaServer 2100 pedestal weighs 114 kg (250 lb) and the AlphaServer 2000 75 kg (165 lb). ²⁴⁾ An AlphaServer 2100 draws up to 880 W with one power supply and 1280 W with two, and is rated at a sound power level of 6.5 B (47 dBA for bystanders). ²⁵⁾

Digital introduced the machine in April 1994 as the Digital 2100 Server A500MP and renamed it the AlphaServer 2100 4/200 in November 1994. ^{26) 27)}

The 21164 arrived with the AlphaServer 2000 5/250 in August 1995, when Digital offered 4/200, 4/233, and 4/275 owners a processor board swap that kept the existing memory, ²⁸⁾ and 21164A 5/375 models followed on 7 November 1996. ²⁹⁾ The successors are the AlphaServer 2100A and 2000A.

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

• AlphaServer 2000 maximum CPUs
  • "Powerup Problem on AS2000", Jay Estabrook, axp-list, 26 Sep 2005: "only 2 CPU boards possible"
  • Alpha AXP System Reference Manual, Version 6, p. D-6, lists three and four CPU Demi-Sable model codes.