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The AlphaPC 164SX is an ATX form factor motherboard for the PCA56 (21164PC), released by Digital in 1997. ¹⁾ It uses the same core logic as the AlphaPC 164LX.

• 400 or 533 MHz PCA56 CPU
• 1 MiB external L2 cache
• 21174-CA chipset
• 4x 168-pin 100 MHz unbuffered SDRAM DIMMs (see below)
• 2x 33 MHz 64-bit PCI slots
• 2x 33 MHz 32-bit PCI slots
• 2x ISA slots
• Cypress CY82C693U-NC EIDE controller and ISA bridge
• SMSC FDC37C669 Super I/O controller
• Floppy disk controller
• PS/2 keyboard and mouse
• 2x RS-232
• 1x Parallel port
• ATX board, 30.48 cm x 24.38 cm (12.0 in x 9.6 in) ²⁾

Instead of jumpers, the board is configured with switchpack SW1; in the manual's tables, 1 is the on position. ³⁾

The 164SX documentation lists only two CPU speed settings, 400 and 533 MHz; the other settings are reserved and have been reported to yield 400 MHz. ⁴⁾ No 600 MHz 164SX was ever made. ⁵⁾

Both 64-bit and 72-bit (ECC) 100 MHz SDRAM modules are supported and must be installed in pairs. Modules up to 128 MiB are officially supported, but some 256 MiB modules also work. The following table lists some RAM modules known to work or not work with the 164SX board.

Unlike the 164LX, the 164SX does not require ECC memory. ⁶⁾ ECC is enabled only if all installed DIMMs are ECC modules, and the DIMMs in each pair must be identical. ⁷⁾ ECC and non-ECC modules should not be mixed. ⁸⁾

As on the 164LX, 4x 256 MiB (1 GiB) is reported to work. ^{9) 10)}

Single-sided Hyundai HY57V28820HCT-H 128 MiB DIMMs were reported not to work. ¹¹⁾

The power supply requirements and the CPU fan connector are the same as on the AlphaPC 164LX: a 300 W supply is sufficient for a typical workstation, and the fan connector has a different pin order from PC fans, whose pins must be rearranged before use. A rewired PC fan ran on a 164SX, but the CPU would not start, because the board did not accept the fan's tachometer signal. ¹²⁾

The flash ROM holds only one console image at a time, either AlphaBIOS or SRM. ¹³⁾ The final releases are SRM V5.8 ^{14) 15)} and AlphaBIOS 5.7. ¹⁶⁾

Switching from AlphaBIOS to SRM is done by copying sx164srm.rom to a FAT-formatted floppy, choosing Upgrade AlphaBIOS, and then power cycling the machine. ^{17) 18)}

The SMMTABLE.TXT file on the V7.3 firmware CD lists SRM 5.8 as the last version for the board but names no update file for it (the entry is [ARCHIVE]NOFILE.EXE). ¹⁹⁾

• SRM V5.8 supports the same Adaptec SCSI controllers on the 164SX as on the 164LX.
• The console's BIOS emulator can initialize ATI Rage 128 and Radeon cards, which older Alpha consoles cannot. ²⁰⁾ PCI Radeon cards were recommended for the 164SX. ²¹⁾

On the 164SX, DIP switch 7 starts the fail-safe booter, which can update the console from a floppy. ²²⁾

Switching from SRM back to AlphaBIOS can fail on the 164SX, as on the 164LX; a workaround is described on the AlphaPC 164LX page. ²³⁾

• 6 beeps: checksum error when the image was read back from memory, reported on a 164SX with newly installed non-ECC DIMMs. ²⁴⁾

Current kernels support the AlphaPC 164SX with CONFIG_ALPHA_SX164; it boots from SRM with aboot. ²⁵⁾ In 2016, Debian's generic 4.x kernels returned to the SRM prompt with "BOOT FAILURE" on the 164SX, while a kernel built for the SX164 booted, ^{26) 27)} so a kernel built with CONFIG_ALPHA_SX164 is the safer choice.

• The PCA56 CPU corresponds to GCC's -mcpu=pca56 ²⁸⁾, and it was the first Alpha CPU to support the MVI instruction set extension. ²⁹⁾ The 21174 core logic supports byte and word access to I/O space, which the kernel enables. ³⁰⁾
• IDE: the onboard Cypress CY82C693 controller uses the pata_cypress driver, which supports DMA. ³¹⁾ Without DMA, the onboard IDE runs in PIO mode and heavy disk I/O severely degrades system performance. ³²⁾
• Cypress IDE DMA transfers can disrupt ISA devices (PCI devices are not affected). ³³⁾
• The SMSC FDC37C669 Super I/O controller provides the floppy controller, serial ports, and parallel port; the Cypress chip provides the keyboard and mouse controller and the time-of-year clock. ³⁴⁾ They use the standard PC drivers:
  • Serial ports: 8250, at the standard PC addresses listed in the Alpha serial port table. ³⁵⁾
  • Parallel port: parport_pc; floppy: floppy; keyboard and mouse: i8042. ^{36) 37) 38)}
  • Clock: the Alpha platform code reads the time-of-year clock itself rather than using rtc-cmos. ³⁹⁾
• USB: the Cypress chip includes a USB controller, which Linux detects, but its pins are not connected to the USB connector footprints on the board. ⁴⁰⁾

• Clock battery: the DS1287-compatible real-time clock is backed up by a replaceable CR2032 coin cell at XB1. ⁴¹⁾ Console settings that do not survive a power cycle usually mean the cell is exhausted; see Systems: Common problems.

• DCG Computers ⁴²⁾
• Enorex ⁴³⁾

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

• ECC memory requirement
  • "Re: PC164SX system building questions", Eric Dittman, axp-list, 21 Apr 1999: "I tried a pair of non-ECC PC-100 memory on mine and they didn't work. I installed a pair of ECC PC-100 memory and they worked."
  • Later reports cited in the Memory section say non-ECC memory works.