 Quote by Jeff Reid
Regarding memory sizes on mainframes, high end IBM 360's and 370's had 1MB or more of memory during the 1960's and 1970's. By 1985, a Cray 2 super computer had 512MB of memory.
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The IBM 360 was constrained to a max of 64k memory.
In the company I worked for, we had 5 370's, the biggest was 512k until 78 when they upgraded to a meg.
I think they did it to support TCAM the predecessor to VTAM.
The IBM 370 was constrained to 268 meg until around 84 when they came out with XA.
That was a PITA due to all the software that had used the upper 4 bits of the address to pass flags.