The AlphaServer 2100A is the successor to the AlphaServer 2100, with the standard I/O functions moved onto the system backplane and most of the EISA slots traded for PCI slots. ¹⁾ The AlphaServer 2000A (Demi-Lynx) is the smaller version, related to the 2100A as the AlphaServer 2000 is to the 2100, holding two CPUs and two memory boards instead of up to four CPUs. ²⁾

• Up to four CPUs, up to 2 GiB of memory (1 GiB with four CPUs), eight PCI slots, and three EISA slots, in the 4/275, 5/250, and 5/300 models ³⁾
• 275 MHz 21064A with 1 MiB of backup cache on the 4/275 models, and a 21164 with 4 MiB of backup cache, at 250 MHz on the 5/250 and 291 MHz on the 5/300 models ⁴⁾
• The later 5/375 models use the KN490 CPU module, a 375 MHz 21164A with 8 MiB of cache, which also fits the AlphaServer 2100 and 2000 ⁵⁾
• The same 128-bit system bus as the AlphaServer 2100, with 666 MB/s peak bandwidth, and memory modules of 64, 128, and 512 MiB ⁶⁾
• 33 MHz PCI and 8.33 MHz EISA, with the standard I/O functions (1 MiB flash ROM, 8 KiB NVRAM, TOY clock, serial, parallel, floppy, keyboard and mouse) on the system backplane rather than a separate I/O module ⁷⁾
• Ethernet is an adapter rather than an onboard controller, unlike the AlphaServer 2100 ⁸⁾
• A low profile rackmount version, the AlphaServer 2100A LP, was also sold; ⁹⁾ Digital announced the 5/375 option for it on 7 November 1996 ¹⁰⁾
• The eight PCI slots are split by an onboard DECchip 21050 PCI-to-PCI bridge: physical slots 4 to 7, the bottom four, are in front of the bridge on the primary PCI bus, and physical slots 0 to 3, the top four, are behind it on the secondary bus ¹¹⁾
• Although the system has three EISA slots, it reuses the AlphaServer 2100's EISA Configuration Utility file, so the ECU shows eight EISA slots; slots 4 to 7 in the ECU, and a power-up ECU error, slot 0, found DEC2A01, expected nothing message, should be ignored ¹²⁾
• Rackmount systems take a second power supply for redundancy. ¹³⁾

The KZPSM and KZPDA PCI adapters need SRM 4.4 or later to work behind the PCI bridge. ¹⁴⁾

Linux 6.9 was the last version to support the AlphaServer 2100A and 2000A, with CONFIG_ALPHA_LYNX; Linux 6.10 removed support for processors older than the EV56 (21164A). ^{15) 16)} Linux 6.10 also removed the Lynx platform entirely, so current kernels do not run even on 5/375 systems with the 21164A. ¹⁷⁾ The 2100A differs from the 2100 in interrupt delivery, so the Sable support that current kernels keep for the 21164A AlphaServer 2100 does not cover it. ¹⁸⁾

• The system backplane carries an NCR 53C810 SCSI controller for the removable media bays; ¹⁹⁾ it uses the sym53c8xx driver. ²⁰⁾
• The final SRM version is V5.3 (see Final versions). For a serial console on COM1, see Using the SRM Console: Serial console.

• Weight, power, and noise: the pedestal 2100A weighs 114 kg, with a maximum usable power of two times 602 W; the rackmount unit weighs 45.4 kg. ²¹⁾ The declared noise level is 47 dBA at the bystander position, idle or operating. ²²⁾
• At most two KFESA or KFESB EISA DSSI controllers can be fitted. ²³⁾
• These options are not supported at all: the DE422-SA EISA Ethernet card, DE425-AA EISA network card, DJ-ML200 PCI NVRAM module, PB2HA-SA EISA Fast SCSI adapter, PB2SX-AA EISA Prestoserve NVRAM, and PBXGA ZLXp-E graphics adapters. ²⁴⁾

Digital did field upgrades of 2100s, with their three PCI slots, to the 2100A. ²⁵⁾ See also the notes on memory and CPU upgrades on the Sable page.