An AlphaStation's SROM

Summary

An AlphaStation's SROM Posted on 2025-03-30 Contents Background I have a thing for weird 90's RISC workstations running UNIX. So when Rob said "Hey, I have an AlphaStation in the boot of my car ..." obviously it came home with me. Unfortunately the AlphaStation is dead. The PSU runs (and stays running, unless the case are disconnected in which case it immediately stops running). The voltages look fine. But the two PCI cards in the machine (a 32-bit Matrox Millenium G200 graphics card and a 64-bit LSI Logic SCSI card) are both dead - neither is detected when inserted into my Pentium 3 PC. And half of the RAM in the first DIMM slot gets very hot. So, I suspect something catastrophic has happened somewhere in its lifetime. But, at least I got a 18GB 1.6" SCSI Hard Drive out of it, and a working (ish) 12x SCSI CD-ROM. VIDEO The AlphaStation 500 This isn't a post about the AlphaStation 500. I'll save that for when (if) I get it working. This is a post about how an AlphaStation 500 boots. But here it is. The AlphaStation 500 is a workstation from Digital, circa 1996. Mine is a 500 MHz model and has an Alpha 21164A processor (aka EV56). And the way it boots is weird. On your common-or-garden PC, there has always been some kind of ROM chip. It holds a piece of firmware known as the BIOS. This ROM chip is available at a well-known location in the processor's address space (remembering that any PC processor boots up in 16-bit, 8088 compatible mode, with a 1 MiB address space, just like an IBM PC 5150) and the processor just starts executing code in it after reset. The Alpha (or at least this AlphaStation 500 - although I think they mostly worked like this) is different. SROM There is a serial ROM (SROM) on the main board, and after reset, some logic internal to the CPU kicks in to generate a clock pulse. This drives an (external) counter, which provides consecutive addresses into the ROM. The 1-bit output of the ROM is sent into the processor, in sync with the clock pulse. Th...