Author here if anyone wants to discuss TI microcontrollers or RAM :-)
dboreham 1241 days ago [-]
If you're looking for suggestions for chips to analyze (unlikely, I realize), a shout out for early 16-bit GI CPUs (so obscure that Google fails to remind me+ of the part#s), or the failed Nat Semi 32-bit chips such as the NS16032 or perhaps the "Basic-on-chip" NS8070.
+Google knows about the CP-1600 but I'm thinking about an earlier design that wasn't single-chip.
kens 1241 days ago [-]
Those chips are probably a bit too obscure for me :-) I tried to figure out what General Instruments CPU you are describing, but the CP-1600 is the only one I could come up with.
theamk 1241 days ago [-]
Coming from discrete logic, a 5 transistor DRAM cell looks strange to me.. the good old “bistable multivibrator” circuit is just 2 transistors (and a few resistors, but I bet many of them could be eliminated with creative transitor sizing)
I am going to guess this design is better in terms of power consumption or total area?
kens 1241 days ago [-]
The cell design strikes me as strange too. According to the patent, static cells require "excessive space", refresh is inconvenient, and previous self-refreshing cells can accumulate erroneous charge. The patent claims all sorts of advantages of minimizing clock voltages, minimizing vias, using a single address line and single data line, etc.
My interpretation is that in the pre-CMOS days, a static cell used too much power due to the load resistor. (The Intel 4004 and 8008 used dynamic storage for registers.) They didn't want to implement a counter for stepping through refresh addresses, so they developed this cell.
(How much did they not want to implement a counter? The program counter is actually a linear-feedback shift register, so it steps through addresses in a pseudo-random order. This saved a few transistors compared to a real counter. The trick is you permute the data in ROM according to the same pattern and everything works just like you had a normal program counter.)
The sharp 4-bit SM590 used as the copyright chip in the NES and the cartages also use this technique.
kens 1241 days ago [-]
I guess it was more common than I thought. It shows how precious every transistor was back then.
dboreham 1241 days ago [-]
According to the patent, the primary benefit is self-refresh, and doing so avoiding substrate charge pump effects.
colejohnson66 1242 days ago [-]
Off topic, but I never fail to see you post these comments on links to your blog. But you’re not the one posting the link, so how do you know when one is posted?
Btw: I love reading these posts. It’s amazing how intricate these tiny things can be!
kens 1242 days ago [-]
Well, I check HN a lot :-)
But also I use f5bot.com, a free service that lets me know if I'm mentioned on reddit or HN. You give it a list of keywords and it emails you if they appear.
johnisgood 1241 days ago [-]
I just want to ask if anyone here still writes code in Forth or not. :D
parsecs 1241 days ago [-]
Not Ken but I've made a few projects with eForth for STM8 if that counts
Rendered at 15:01:40 GMT+0000 (Coordinated Universal Time) with Vercel.
+Google knows about the CP-1600 but I'm thinking about an earlier design that wasn't single-chip.
I am going to guess this design is better in terms of power consumption or total area?
My interpretation is that in the pre-CMOS days, a static cell used too much power due to the load resistor. (The Intel 4004 and 8008 used dynamic storage for registers.) They didn't want to implement a counter for stepping through refresh addresses, so they developed this cell.
(How much did they not want to implement a counter? The program counter is actually a linear-feedback shift register, so it steps through addresses in a pseudo-random order. This saved a few transistors compared to a real counter. The trick is you permute the data in ROM according to the same pattern and everything works just like you had a normal program counter.)
https://patents.google.com/patent/US3876993A
The sharp 4-bit SM590 used as the copyright chip in the NES and the cartages also use this technique.
Btw: I love reading these posts. It’s amazing how intricate these tiny things can be!
But also I use f5bot.com, a free service that lets me know if I'm mentioned on reddit or HN. You give it a list of keywords and it emails you if they appear.