Qbus split I&D?

[Eric Smith]

On Mon, Mar 16, 2015 at 9:10 PM, Christian Gauger-Cosgrove
<captainkirk359 at gmail.com> wrote:
> Unfortunately, the cost of MRAM chips is rather a lot, especially
> since you can't just order small batches. Minimum order on Mouser was
> 128 chips at something like $20 CAD per.

Digi-key sells them without any minimum order quantity. Their quantity
1 price for the 1Mx16 35ns TSOP-54 device (p/n MR4A16BYS35) is $36.72.

Not including parity or ECC, it takes two devices to fill the entire
4MB address space of the PDP-11/70. Either parity or ECC will require
another one additional device, which won't be fully utilized.

Ordinary SRAM is cheaper, but $110.16 for enough RAM chips to max out
a PDP-11/70 doesn't seem all that expensive, unless you're comparing
to DDR SDRAM DIMMs for PCs.