Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
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Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
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Re: Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
#2I love these die shot RE walkthroughs. This is such a weird choice though; almost no one used this chip for production hardware. The WD 17xx series was the king of floppy controllers in the 70's and early 80's (well, if you ignore Woz's masterpiece, which was discrete logic).
Seems like if you're going to reverse an obscure chip, something with a more exotic application would have been more fun?
Re: Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
#3I love these die shot RE walkthroughs. This is such a weird choice though; almost no one used this chip for production hardware. The WD 17xx series was the king of floppy controllers in the 70's and early 80's (well, if you ignore Woz's masterpiece, which was discrete logic). Seems like if you're going to reverse an obscure chip, something with a more exotic application would have been more fun?
We definitely wanted fun! I guess there are two ways to slice and dice it: 1) fun because the application is exotic / iconic, or 2) fun because the chip is exotic. This is definitely a case of the latter: an exotic chip with interesting history.
Re: Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
#4Incredible stuff!
Re: Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
#5My guess is that, at some point, a manager at Acorn asked which disk controller would the engineers recommend and they, obviously joking, said "8271".
When they realized what they had done, it was too late.
Re: Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
#6I love these die shot RE walkthroughs. This is such a weird choice though; almost no one used this chip for production hardware. The WD 17xx series was the king of floppy controllers in the 70's and early 80's (well, if you ignore Woz's masterpiece, which was discrete logic). Seems like if you're going to reverse an obscure chip, something with a more exotic application would have been more fun?
> Woz's masterpiece, which was discrete logic
It had the downside of requiring precise timing. This is an issue if you wanted a faster (or even a slightly improved) 6502 in the machine.
Oh well...
Re: Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
#7My guess is that, at some point, a manager at Acorn asked which disk controller would the engineers recommend and they, obviously joking, said "8271". When they realized what they had done, it was too late.
If this in the context of the BBC Micro, Acorn had already used the 8271 for floppy support with previous “System” and “Atom” models[1], so it’s probably chosen through inertia from a previous design choice.
As for the older systems, does anyone have a date for the WD 1771 (the more common alternative)? The data sheet shown on the Wikipedia page is dated April 1979, and if that’s the release date then it would have been a new, unproven part compared to the intel chip when the System and Atoms were released 1979/80, assuming the floppy drive was an early upgrade (again, I don’t have dates to hand).
[1] http://chrisacorns.computinghistory.org.uk/8bit_Upgrades/Aco...
Re: Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
#8My guess is that, at some point, a manager at Acorn asked which disk controller would the engineers recommend and they, obviously joking, said "8271". When they realized what they had done, it was too late.
If this in the context of the BBC Micro, Acorn had already used the 8271 for floppy support with previous “System” and “Atom” models[1], so it’s probably chosen through inertia from a previous design choice. As for the older systems, does anyone have a date for the WD 1771 (the more common alternative)? The data sheet shown on the Wikipedia page is dated April 1979, and if that’s the release date then it would have b…
Google Books shows the WD1771 available and in use in 1977 with more products using it in 1978.
(I find Google Books very useful for this sort of archaeology. Change the time range to "1977-1980", search for "wd1771", and then sort by date. Of course this isn't thorough, but it gives a good overview for little effort.)
Re: Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
#9Earlier quoted context omitted.
If this in the context of the BBC Micro, Acorn had already used the 8271 for floppy support with previous “System” and “Atom” models[1], so it’s probably chosen through inertia from a previous design choice. As for the older systems, does anyone have a date for the WD 1771 (the more common alternative)? The data sheet shown on the Wikipedia page is dated April 1979, and if that’s the release date then it would have b…
Google Books shows the WD1771 available and in use in 1977 with more products using it in 1978. (I find Google Books very useful for this sort of archaeology. Change the time range to "1977-1980", search for "wd1771", and then sort by date. Of course this isn't thorough, but it gives a good overview for little effort.)
Thank you for the research. In that case I guess it’s more of a wrong bet on part choice in 1979 I guess.
Re: Reverse engineering a forgotten 1970s Intel dual core beast: 8271, a new ISA
#10The decision to use this chip (vs the WD) in the BBC Micro made me wonder if there were other obvious-in-hindsight bad/weird/hackish choices in classic computer design?
The PC-AT's use of the keyboard controller to control A20 and CPU reset comes to mind.
Any others?