The ES40 is a four-processor 21264 server, sold in tower, pedestal, and rackmount enclosures. ¹⁾ Its firmware also covers the ES40cv, ES40lp, TS40, and TS20. ²⁾

Except where noted, the following comes from the systems and options catalog. ³⁾

• Up to four 21264 CPUs: 500 MHz 21264 (EV6) with 4 MiB of secondary cache each, ⁴⁾ or, later, 667 MHz 21264A (EV67) or 833 MHz 21264B (EV68) CPUs with 8 MiB of secondary cache each ^{5) 6)} (see Conflicting information)
• 21272 (Tsunami) core logic ⁷⁾
• Model 1 has six 64-bit PCI slots and room for four memory options; Model 2 has ten 64-bit PCI slots and room for eight
• Memory options are sets of four DIMMs; each memory array must use one DIMM type, because the stacked and monolithic MS610-DA and MS610-EA options share part numbers but are not interchangeable ⁸⁾
• The Model 2 has 32 DIMM slots. ⁹⁾ The console configures memory four-way interleaved when all four arrays hold the same size, and two-way plus one separate array when three do. ¹⁰⁾
• 1.44 MB floppy drive, CD-ROM, two EIA-232 serial ports, one bidirectional enhanced parallel port, a dedicated serial port for the remote management console (RMC), keyboard and mouse ports
• Up to two internal disk drive cages, each with a one-port Ultra2 SCSI adapter and four 3.5-inch disks; StorageWorks shelves are also supported

• On the ES40, the SRM console's os_type variable takes unix, vms, or linux, and all three start the SRM console at power-up or reset; ¹¹⁾ AlphaBIOS is started from SRM with the alphabios command. ¹²⁾
• The SRM console sizes its own heap for the installed options, so a heavily populated machine goes through one or more visible crash and reboot cycles the first time, printing "Console heap space will be automatically increased in size by 64KB" before restarting with the larger heap. No action is needed. show heap_expand shows the size, and set heap_expand none restores the default, which should be done after a configuration change. ¹³⁾
• SRM V5.6 added "an X86 bios emulator" to support the KZPCC-CE RAID controller (see Other Hardware). ¹⁴⁾
• A failed update to SRM V5.8 can leave a TIG error on the operator control panel. Removing MMB1 and moving jumper J21 to position 2-3 forces the TIG NVRAM to be reloaded from the serial ROM, which avoids replacing the system board. ¹⁵⁾
• Some ES40s shipped with jumper J31 in position 1-2 rather than the documented default of 2-3, which made COM1 unreachable through the RMC's modem port; J31 is not described in the owner's guide. ¹⁶⁾

Current kernels support the ES40, with CONFIG_ALPHA_DP264 or a generic kernel, booted from the SRM console with aboot; see Installation. The ES40 has no MILO. ¹⁷⁾ Use the final SRM version, V7.3-1 (see Final versions). QEMU emulates an ES40-class system (see Emulators). See also Tsunami systems.

• The onboard Acer Labs M1543C bridges the first PCI bus to ISA and contains two IDE controllers, with the CD-ROM on the first, and a USB controller. ^{18) 19)} The IDE controllers use the pata_ali driver, and the USB controller the ohci-pci driver. ^{20) 21)}
• The KZPBA-CA UltraSCSI adapter in Compaq's ES40 catalog ²²⁾ is a QLogic ISP1040B card, ²³⁾ which uses the qla1280 driver and needs its firmware from linux-firmware. ²⁴⁾
• The serial console is COM1, which the remote management console (RMC) shares; see Using the SRM Console: Serial console and Remote management for the settings and the RMC escape sequence.

• Weight, power, and noise: a tower ES40 weighs 65 kg typically and up to 96 kg, and a pedestal 127 kg typically. The power supplies are universal, auto-ranging units for 100 to 120 V and 200 to 240 V; a tower or rackmount system dissipates 900 W nominally and up to 1300 W. The declared noise level is 48 dBA at the bystander position, idle or operating. ²⁵⁾
• Only one VGA-enabled graphics card is supported in the PCI 0 slots. ²⁶⁾
• Unplugging the mouse at the SRM console stops the keyboard from responding until the mouse is reconnected. ²⁷⁾
• ES40 memory is sensitive to how DIMMs are seated, and a bad connection is easy to make. ²⁸⁾

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

• 833 MHz CPU
  • Compaq AlphaServer ES40 Systems Technical Summary, pp. 1, 14, lists the 833 MHz CPU as a 21264A.
  • "Re: ES40, ES45, etc. support?", Michael L. Hitch, port-alpha, 30 Jun 2004: a four-CPU 833 MHz ES40 identifies its CPUs as 21264B.
• ES40 maximum memory
  • "Re: In sdearch of an 8GB machine (fwd)", Peter Rival, axp-list, 11 Sep 2000: "an ES40 maxes out with 32GB. I believe when they first came out it was 16GB"
  • "Memory max on Compaq AlphaServer running Linux", Lew Randerson, axp-list, 27 Nov 2000: "2GB is the max on Compaq's Linux-Ready AlphaServer ES40"