3 ms·

> But what kind of clock frequency would you get from that kind of a setup? One chip gave you much better performance. You might be surprised, because the answ

by retrac 7y ago

> But what kind of clock frequency would you get from that kind of a setup? One chip gave you much better performance. You might be surprised, because the answer is in the ballpark of 100 MHz when cost is no object. When cost is an object, well even simple designs like the MSI/LSI versions of the PDP-8 were clocked around a 1 microsecond memory cycle, comparable to most early microprocessors. For an extreme example, the Cray-1 was constructed entirely from tens of thousands of discrete NOR gate chips using ECL, and was clocked at 80 MHz. Multi-chip implementations remained standard on big systems into the 1980s. The ability to use bipolar technology over the much slower (at the time) MOS was a major factor, but it also simply wasn't possible to add to a single die sophisticated features like large register sets, pipelining, caches, etc. with the limited transistor budget available in the 1970s. It wasn't until the mid-80s that CMOS microprocessors started to win decisively versus discrete logic for mid-range applications. It lasted even longer on the very high end -- DEC, IBM, Cray, and others, were manufacturing processors constructed out of many MSI/LSI chips well into the 1990s. Even the first POWER processor from IBM consisted of 9 VLSI chips, in 1990. The overwhelming advantage for single-chip processors back then was the low cost. A minicomputer like the PDP-11/20 from all the way back in 1970 constructed out of SSI chips could run circles around the 6502, but the processor for the PDP-11/20 was like $2000 and the 6502 was $25.

Taniwha 7y ago
I completely agree with all your points, but would add that we also didn't have the CAD tools to make big stuff, the 6502 was built by cutting litho to make transistors (actually physically cutting different coloured transparent tape and sticking it to a transparent sheet), nowadays I could knock out all fully timed 6502 in a few days with the right tools. Building something the size of a Cray on paper was an amazing achievement
TheOtherHobbes 7y ago
The approximate timeline (after valves) was discrete transistors, preassembled transistor modules, gate-level SSI, logic-level TTL SSI/MSI, bit-slice MSI/LSI, and VLSI, with MOS VLSI as a spin-off that eventually ate the industry. ECL for super high performance applications ran along a parallel slightly slower path. ECL was always a power-hungry monster and it was obvious it was eventually going to overtaken by improvements in VLSI - although this didn't happen definitively until the 90s. The low cost of the 6502 wasn't just about low cost as a number; it was about consumerisation and personalisation. A 6502 8-bitter was a very slow, limited machine - but it was your slow, limited machine. You could buy it retail and all of its cycles were yours. Smaller PDP-11s could also be personalised, and eventually you could buy LSI versions of the architecture. But the sales channels were almost exclusively corporate/industrial/academic - and so were the prices. (Heathkit actually sold an LSI-11 kit, but it was priced at $$$$$ and hardly anyone could afford it.)
- davidgould 7y ago
  > Smaller PDP-11s could also be personalised, and eventually you could buy LSI versions of the architecture. But the sales channels were almost exclusively corporate/industrial/academic One of the great missed opportunities. I remember drooling over the DEC VT-103 in late 1979. This was a VT-100 terminal with an LSI-11 inside along with a TU-58 tape drive (one of the variety of strange little tape drives DEC were so fond of). It ran RT-11 (the inspiration for CP/M) which was a mature system with lot of software and good documentation. This would have made a really sweet personal computer with floppies instead of the TU-58. Had DEC marketed it as such back in 1979 might have forestalled the IBM PC. I wanted one really badly, and the pricing was not that bad for the time, but there was no way to get one as an individual. They were only sold to large companies or integrators for factory automation projects and such like. Two years ahead of the IBM PC DEC had a factory churning out better systems with great software and all the development costs already paid for. Imagine what might have happened if they had thought to actually sell them to anyone who wanted one.
leoc 7y ago
The Intel 8008 was designed for what is arguably the first personal computer, but its designers ended up going with a TTL CPU instead, partly because it was faster: https://www.righto.com/2015/05/the-texas-instruments-tmx-1795-first.html https://www.righto.com/2015/05/the-texas-instruments-tmx-179... .

by retrac 7y ago

Taniwha 7y ago

I completely agree with all your points, but would add that we also didn't have the CAD tools to make big stuff, the 6502 was built by cutting litho to make transistors (actually physically cutting different coloured transparent tape and sticking it to a transparent sheet), nowadays I could knock out all fully timed 6502 in a few days with the right tools. Building something the size of a Cray on paper was an amazing achievement

TheOtherHobbes 7y ago

The approximate timeline (after valves) was discrete transistors, preassembled transistor modules, gate-level SSI, logic-level TTL SSI/MSI, bit-slice MSI/LSI, and VLSI, with MOS VLSI as a spin-off that eventually ate the industry. ECL for super high performance applications ran along a parallel slightly slower path. ECL was always a power-hungry monster and it was obvious it was eventually going to overtaken by improvements in VLSI - although this didn't happen definitively until the 90s. The low cost of the 6502 wasn't just about low cost as a number; it was about consumerisation and personalisation. A 6502 8-bitter was a very slow, limited machine - but it was your slow, limited machine. You could buy it retail and all of its cycles were yours. Smaller PDP-11s could also be personalised, and eventually you could buy LSI versions of the architecture. But the sales channels were almost exclusively corporate/industrial/academic - and so were the prices. (Heathkit actually sold an LSI-11 kit, but it was priced at $$$$$ and hardly anyone could afford it.)

davidgould 7y ago
> Smaller PDP-11s could also be personalised, and eventually you could buy LSI versions of the architecture. But the sales channels were almost exclusively corporate/industrial/academic One of the great missed opportunities. I remember drooling over the DEC VT-103 in late 1979. This was a VT-100 terminal with an LSI-11 inside along with a TU-58 tape drive (one of the variety of strange little tape drives DEC were so fond of). It ran RT-11 (the inspiration for CP/M) which was a mature system with lot of software and good documentation. This would have made a really sweet personal computer with floppies instead of the TU-58. Had DEC marketed it as such back in 1979 might have forestalled the IBM PC. I wanted one really badly, and the pricing was not that bad for the time, but there was no way to get one as an individual. They were only sold to large companies or integrators for factory automation projects and such like. Two years ahead of the IBM PC DEC had a factory churning out better systems with great software and all the development costs already paid for. Imagine what might have happened if they had thought to actually sell them to anyone who wanted one.

leoc 7y ago

The Intel 8008 was designed for what is arguably the first personal computer, but its designers ended up going with a TTL CPU instead, partly because it was faster: https://www.righto.com/2015/05/the-texas-instruments-tmx-1795-first.html https://www.righto.com/2015/05/the-texas-instruments-tmx-179... .