5 ms·
ECL logic systems reached effective clock frequencies in excess of 500 MHz in the late 60s or so. It was extremely fast compared to contemporary RTL/TTL logic.
by blattimwind 7y ago
ECL logic systems reached effective clock frequencies in excess of 500 MHz in the late 60s or so. It was extremely fast compared to contemporary RTL/TTL logic.
- cptnapalm 7y agoI had not heard of ECL before. Thank you for popping in with this.
- bonzini 7y agoThese days ECL lives on as CML, which is similar and mostly used for signal transmission. It's very fast so HDMI uses it. Some crypto circuits use CML logic too, because it's less susceptible to side channel attacks.
- dfox 7y agoAlmost all modern fast serial interfaces are descended from ECL. Often with a twist that while receiver is ECL/CML-style long-tailed pair (which is the obvious implementation of comparator), the transmit side is normal CMOS totem-pole output stage coupled with some passive network to produce right voltage levels (and right output impedance).
- analognoise 7y agoWait, what? You can do a MOS long-tail pair just fine, can't you? Similarly for a totem pole with BJTs. They're topological circuit constructions that work for either family - aren't they?
- deleted 7y ago[deleted]
- mark-r 7y agoI worked at the company Jim Thornton founded after he left CDC, Network Systems. Each network adapter box had a custom processor implemented in ECL.
- ajross 7y agoExactly. It was MOS that lagged, not "transistors" or "computers", really. Transistorized microwave circuits (analog, not digital) in the GHz range were operating as early as the 1960's too. MOS is just hard. It's hard to fabricate, it's hard to design (i.e. you need computers to make computers!), it's hard to scale. It required new chemistries be invented and new circuit design techniques to manage the (really tiny!) components. So for a long time you could have a big circuit in discrete bipolar components which ran fast or a tiny one in MOS which was slow. But MOS was tiny and MOS was cheap. So by the early 90's it had caught up in speed with all but the fastest discrete technologies (GaAs was "right around the corner" for like two decades as it kept getting lapped by routine process shrinks -- now no one remembers it) and the market abandoned everything else.
- kken 7y ago>MOS is just hard I think the important point is that "MOS scales". All the bipolar technologies never had anything like Dennard scaling, which was the backbone of Moores Law.
- blattimwind 7y agoCase in point, you could get bipolar ECL RAM in the 80s with access times of around 1-2 ns (which is at least four times faster than the fastest DDR-SDRAM in 2020). Except those things would have a few kilobits at most and burn a Watt or two; an entire 16 GB stick of DDR4 doesn't require much more than that. (This is SRAM of course; you can't build good DRAM on a bipolar process, and MOS SRAM is much faster than DRAM as well. However, MOS SRAM in the 80s would have access times of 20-150 ns; it's typically the suffix of the part number, e.g. 62256-70)