IBM System/370 – 1970

IBM introduced the 12.5MHz cabinet sized System/370 in June 1970 as an evolution of the System/360 from 1964.  These systems formed the entire base of IBM’s mainframe business.  Today’s System z, itself an evolution of the original System/360 and 370, can still run many of the original programs, unmodified, from 50 years ago.  This is a testament to 2 things, the wide adoption of the IBM systems, and the forward thinking of IBM.  Even the original System/360 from 1964 was a full 32-bit computer.  Single chip processors did not embrace 32 bit architectures until the very early 1980’s (Motorola 68k, National 32k, etc).

In 1980 IBM sought to make a single chip version of the 370, in an effort to make a version that could be used for desktop type computers.  This was to become the Micro/370.  There were 2 distinct products to come out of this goal that are widely confused and debated.  The first became the PC XT/370, an add in card(s) for an IBM PC to give it the capability to run System/370 software.  Later another version was developed called the Micro/370 as a single chip solution.

The PC XT/370 began as an experiment,  a test bed implementation of the System/370 in a microprocessor environment.  The goal was not to rebuild the 370 from the ground up (that would come later) but to merely implement its instruction set into an existing design.  The base processor had two main requirements:  it had to be 32 bits, and it had to be microcoded.  IBM’s engineers in Endicott, NY selected the then very new Motorola MC68000 processor as their basis.  It was one of the only 32-bit designs at them time so that no doubt helped in the selection process.

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Apple recently released the new (or rather updated) Macbook Air.  21 years ago they released their first laptop, the Mac Portable.  It was not the success that Apple hoped, but the later PowerBook was. Mr. McCarron recently posted a pic of these side by side.

Mac Portable and Macbook Air

Needless to say in 21 years Apple was improved their laptops a fair amount. However there are some similarities.  The Macintosh Portable shipped with no physical hard drive (a 20 or 40mb one was available as an option). It had 256k of onboard ROM (truly solid state storage).  If you wanted more, you were stuck with floppies. Its RAM was handled by 1MB (expandable to 9MB) of SRAM, which was faster (then DRAM), and allowed an actual sleep mode. Technologizer did a tear down of one last year for its 20th anniversary which shows the guts rather well.

MC68HC000FN16

The CPU was a 16MHz CMOS version of the Motorola MC68000 (MC68HC000FN12F).  The 12F is an ‘uprated’ 12MHz CPU that would run at 16MHz.  Later Motorola released it as a standard part (the FN16 pictured here)  The chipset was provide by VLSI who would go on to make the first ARM CPUs for the Newton line with Apple.

Just a few quick comparisons.  The entire memory of the Mac Portable would fit in the L1/L2 cache of the CPU on a Macbook Air.  The battery for the portable? 2.7lbs, heavier then the entire Air.