Yuhong Bao (yuhongbao_386.delete@this.hotmail.com) on January 3, 2021 1:51 pm wrote:
> Adrian (a.delete@this.acm.org) on January 3, 2021 1:14 pm wrote:
> > Tim McCaffrey (timcaffrey.delete@this.aol.com) on January 3, 2021 9:28 am wrote:
> > >
> > > Parity existed on every motherboard until EDO DRAM got introduced.
> > > I think there were a couple of factors:
> > > 1) EDO DRAM, IIRC, was produced in a x8 package only, there was no x1 (or x9) package.
> > > (This made adding a parity bit difficult).
> > > 2) ECC is a pretty big step up (when EDO was introduced) in the memory controller,
> > > easier to just not include it.
> > > 3) At the time EDO was introduced, memory was very expensive (I paid $300 for 8 Meg
> > > at that point in time, of course memory prices crashed right after that :( ).
> > > 4) Once motherboard & memory controller (north bridge) vendors got away without supporting
> > > parity for a couple of years, everybody was cutting that corner to stay competitive.
> > >
> > > ECC was first available in servers because customers demanded it.
> > > I'm not sure, to this day, how much the various OSes actually support reporting
> > > ECC corrections or how proactive they are isolating questionable memory.
> > > I know the mainframes I worked on were able to hot swap out bad memory, which was
> > > a big selling point (and required lots of OS support). Of course, these days
> > > you can just migrate the VM to another host, but you still need to be able to
> > > flag when bad things are happening.
> >
> >
> > I have actually used 16 Mbytes of EDO memory with parity on my Pentium motherboard. Unfortunately,
> > the motherboard used the evil Intel Triton chipset, which did not check the parity.
> >
> >
> > I had bought the memory before the motherboard. The new Intel policy
> > of omitting error detection support was a surprise for me.
> >
> > The EDO modules with parity (4 Mbyte per module, with 5 packages on a single
> > side) used one smaller x4 memory package for each 4 larger x8 packages.
> >
> >
> > Many of the other EDO modules that I have seen, without parity, had in fact the same PCB layout as
> > my modules with parity, except that the central small x4 package was not soldered on the modules.
> >
>
> I think ECC was designed specifically so that obsolete x1 and "quad CAS" chips would not be needed
> unlike with parity. Even before Triton PC OEMs was already eliminating parity on desktop PCs.

Seems that Gateway was one of the first to do it (back in 1993): https://groups.google.com/g/alt.sys.pc-clone.gateway2000/c/GXYfXOeN9Fs/m/rbpf2gkwlCQJ