The AlphaPC 164RX is an ATX form factor motherboard from Digital's OEM line, based on the 21164PC (PCA57) microprocessor and the VLSI Technology Polaris system controller. Its Linux platform name is RX164. It was announced in 1998, but only a small number of boards were built. It can only boot Linux through MILO, and no current kernel has been reported to boot on it.

• 525 or 600 MHz 21164PC CPU ¹⁾
• 1 MiB pipelined burst SRAM L2 cache
• VLSI Technology Polaris system controller, memory bus at 75 MHz
• 2 or 4 168-pin PC100 unbuffered SDRAM DIMMs, supports 64 MiB to 512 MiB
• 5x 5V 32-bit 30 MHz PCI slots (one behind a PCI-to-PCI bridge, shared with the ISA slot)
• 1x ISA slot (shared)
• 10/100 Mb/s Ethernet
• PCI IDE (PIO mode 4) with UltraDMA support
• Floppy, 2x UARTs, parallel port, keyboard and mouse, real-time clock
• 2x USB ports ²⁾
• 1 MiB flash ROM
• Windows NT AlphaBIOS firmware
• ATX form factor and standard ATX power supply ³⁾

No SRM console was released for the board, ⁴⁾ so Tru64 UNIX and the current distribution installers, which boot from SRM, cannot be used.

Current kernels include support for the board (CONFIG_ALPHA_RX164, or a generic kernel, with Polaris support in core_polaris.c), ⁵⁾ but it can only boot Linux through a MILO built for it by Jay Estabrook. ⁶⁾ Released MILO versions cannot load kernels from Linux 2.6.23 on, which added a program header that MILO mistook for a loadable segment; a MILO fix was committed in May 2026 but has not been tested on this board. ⁷⁾ See MILO: Booting Linux.

Digital announced the AlphaPC 164RX together with the AlphaPC 264DP in November 1998. Both were in beta at the time and were expected to enter production in January 1999. ⁸⁾

The board would have been the first to use the PCA57, a respin of the PCA56 (21164PC) that performs nearly as well as the EV56, and the Polaris core logic, which supports only 32-bit PCI. ⁹⁾ Production was reportedly delayed by a bug in the chipset ¹⁰⁾, and the board was never sold as a product. ¹¹⁾ At least 12 boards were built, and some reached users. ¹²⁾

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

• CPU speeds
  • AlphaPC 164RX Motherboard Product Brief: "operating at speeds of 525 or 600 MHz"
  • "Re: Kernel 2.4.17", Jay Estabrook, axp-list, 8 Jan 2002: "RX164 PCA57 (525) POLARIS AlphaPC164-RX (no product)"
• PCI slots
  • AlphaPC 164RX Motherboard Product Brief: "One ISA expansion slot (shared with the bridged PCI slot)"
  • "RE: Questions on Alpha/Linux.", Chris Boyer, axp-list, 1 Mar 2000: "6 PCI slots (all 32s) / 1 ISA Slot"