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Naked at 30: Osborne 1 stripped to its chips

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When chip pins were few and far between

Every time I open up heirloom hardware, I'm always amazed at how few pins that chips had in the early days. And, for that matter, how comparatively huge the pins were in that previous millennium. Take a look, for example, at this close-up of (clockwise from left) the Osborne 1's CPU, one of its peripheral-interconnect chips, and its floppy-drive controller chip:

Osborne 1, second version - chips on logic board

At the intersection of D780C-1, MC6821P, and MB8877 (click to enlarge)

Following the hefty, hefty, hefty theme, the Osborn 1's logic board is not eactly what you might call a marvel of miniaturization at 16.5-by-7.25 inches (41.9-by-18.4 centimeters).

Osborne 1, second version - logic board

I counted them so you don't have to: the Osborne 1's logic board is home to 107 chips (click to enlarge)

A Zilog-IP NEC D780C-1 Z80 CPU running at 4MHz graces the logic board's center, flanked by two Motorola MC6821P peripheral-interconnect chips.

Osborne 1, second version - Z80 microprocessor

The 4MHz Z-80–based NEC D780C-1 CPU (click to enlarge)

A Fuji MB8877 floppy-disc controller (well, I believe it's a Fuji – if you know better, let me know) sits above one of the MC6821Ps, and to the right of that same peripheral-interconnect chip squats a Motorola MC6850P asynchronous communications interface adapter chip.

Osborne 1, second version - floppy-disc controller chip

The Fuji MB8877 floppy-disc controller (click to enlarge)

Osborne 1, second version - peripheral-interconnect chip

One of the two Motorola MC6821P peripheral-interconnect chips (click to enlarge)

Osborne 1, second version - asynchronous communications interface chip

The Motorola MC6850P asynchronous communications interface adapter chip (click to enlarge)

Osborne 1, second version - ROM chip

The Rev. A ROM (click to enlarge)

Osborne 1, second version - ROM chip

The Rev. 1.43 ROM, with date of issue (click to enlarge)

On the far right, occupying a little less than a third of the logic board, is an array of 32 16-pin chips; 27 are AMD AM9016FPCD 16Kb DRAM chips. Interspersed among those AMD chips are five identically sized 16-pin chips, one labled B8226 G and four labled B8229 G.

Osborne 1, second version - DRAM array

Thirty-two chips, 64KB of DRAM (click to enlarge)

Considering that the Osborne 1 had 64KB of DRAM, I'd bet the farm that those five oddballs are also 16Kb DRAM chips, seeing as how 32 16Kb chips would be needed to provide 64KB of DRAM.

Osborne 1, second version - DRAM detail

The AMD DRAM chip (top), with the unknown DRAM chip below it (click to enlarge)

Unfortunately, the only info I could find on the intertubes about any chips labled B8226 and B8229 were a few references to Bay Linear surface-mount, zero-bias Schottky detector diodes – but even though I'm not in the least bit an EE kinda guy, that doesn't make any sense to me.

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