Look at this beautiful 1 GHz #Alpha #CPU from an #HP/#Compaq #AlphaServer DS15

[dersammler@oldbytes.space]

Look at this beautiful 1 GHz #Alpha #CPU from an #HP/#Compaq #AlphaServer DS15.

The underside does not have pins, but holes in which wires end. These wires are touching the contacts on the motherboard. There's no socket whatsoever. Weird design.

#RetroComputing #DEC #digital #AXP

[winterschon@mastodon.bsd.cafe]

@derSammler those are good examples of Ball Grid Array and Land Grid Array, e.g. BGA and LGA cores. The BGA page has examples of many sub-types, and links to the other primary designs, kinda worth a look:

https://en.wikipedia.org/wiki/Ball_grid_array

There's so much fun to be had with old CPU collections, especially vintage alternate types like the Alpha. Sun UltraSparc and PowerPC from the same era also have some beautiful examples.

That DS15 CPU is a classic (https://en.m.wikipedia.org/wiki/Alpha_21264), very interesting early example of using branch prediction calculations to accelerate cache reads vs suffering potential cycle penalties and stack eviction.

> The predictor was used as the Alpha 21264 has a minimum branch misprediction penalty of seven cycles. Due to the instruction cache's two cycle latency and the instruction queues, the average branch misprediction penalty is 11 cycles. The algorithm maintains two history tables, Local and Global...

> The local predictor consists of a 1,024-entry by 10-bit branch history table... Each entry is a 3-bit saturating counter. The value of the counter determines whether the current branch is taken or not taken.

> The global predictor is a single-level, 4096-entry branch history table. Each entry is a 2-bit saturating counter; the value of this counter determines whether the current branch is taken or not taken.

ok ok, enough of this nerdery. there are Alpha 21264 CPUs on eBay if anyone wants to own a piece of this wonderful engineering. https://ebay.us/m/ttryzO