[Info-vax] OT: parity vs ECC on EV4

[Michael Moroney]

John Wallace <johnwallace4 at yahoo.co.uk> writes:

>Wrt AlphaStation 200: what leads you to think it has ECC? The
>"AlphaStation 200 Series: User Information" book at
>http://www.compaq.com/alphaserver/download/ek-pcdta-ui-e01.pdf
>says, in the Motherboard section in chapter 2, "Memory controller and
>data path that connects through a 64-bit wide data bus to main
>memory and through a 128-bit wide data bus to second-level cache. The
>data is longword (32-bits) parity protected. "

The Alphastation 200 used one parity bit to cover each longword (32
bits) of memory.  It used the then-standard 36 bit 72 pin parity SIMMs.
Digital even sold 33 bit memory for it for a while.  (was supposed to be
cheaper because it needed 33/36 as many memory cells, but in reality, 
wasn't)