The CDP1802 is a 8bit CMOS processor introduced by RCA back in 1976. It is fully static meaning the clock input can be stopped, saving power without affecting registers/status. Famously, it was used on the Galileo spacecraft. Since it's nearly Christmas, 2nd photo is a COSMAC ELF ... on a shelf 😉
December 11, 2024 at 8:22 PM
The CDP1802 is a 8bit CMOS processor introduced by RCA back in 1976. It is fully static meaning the clock input can be stopped, saving power without affecting registers/status. Famously, it was used on the Galileo spacecraft. Since it's nearly Christmas, 2nd photo is a COSMAC ELF ... on a shelf 😉
Wasn't that based on the CDP1802 processor and the CDP1861 video chip? I ended up building one of the "Elf" computers (wire-wrapped!) as a teen... it's a weird machine.
September 24, 2026 at 3:01 PM
Wasn't that based on the CDP1802 processor and the CDP1861 video chip? I ended up building one of the "Elf" computers (wire-wrapped!) as a teen... it's a weird machine.
New blog post! Taking a deeper look at the RCA Studio II with some help from a package of goodies from Belgium nicole.express/2025/rca-stu...
The RCA Studio II Lives On: A Package from Belgium
The RCA Studio II and its CDP1802 chipset had much more support from enthusiasts than it did the wider video game market. But I shouldn’t put “had” in the pa...
nicole.express
February 10, 2025 at 12:39 AM
New blog post! Taking a deeper look at the RCA Studio II with some help from a package of goodies from Belgium nicole.express/2025/rca-stu...
All the guides I can find agree with it being the CDP1802. I haven't seen mine in 35+ years. Short of an emulator, getting a real one running would require a LOT of specific parts. (the combination power/video switch box)
September 24, 2026 at 3:29 PM
All the guides I can find agree with it being the CDP1802. I haven't seen mine in 35+ years. Short of an emulator, getting a real one running would require a LOT of specific parts. (the combination power/video switch box)
last year for me it was exploring the COSMAC ELF and VIP, RCA CDP1802 architecture
May 24, 2026 at 8:38 PM
last year for me it was exploring the COSMAC ELF and VIP, RCA CDP1802 architecture
But what it did was introduce me to the idea that for all the successful computers out there - Spectrums, C64s, Beebs - there were computers I might never see, quirky oddities like this CDP1802 powered beauty with it's dinky joystick. Apparently it was (relatively) big in the Netherlands!
January 12, 2025 at 2:30 PM
But what it did was introduce me to the idea that for all the successful computers out there - Spectrums, C64s, Beebs - there were computers I might never see, quirky oddities like this CDP1802 powered beauty with it's dinky joystick. Apparently it was (relatively) big in the Netherlands!
COSMACもやっています。
kanpapa.com/cosmac/
kanpapa.com/cosmac/
COSMAC研究会
1970年代のCOSMAC CPU(RCA CDP1802)でレトロなマイコンシステムの実験をしているCOSMAC研究会です。
kanpapa.com
February 13, 2024 at 10:06 PM
COSMACもやっています。
kanpapa.com/cosmac/
kanpapa.com/cosmac/
playing one of the few Space Invaders ports for COSMAC ELF written in CDP1802 assembly, with no CHIP-8 interpreter.
it uses the PIXIE (CDP1861)’s highest available resolution mode, 64x128.
it uses the PIXIE (CDP1861)’s highest available resolution mode, 64x128.
December 14, 2025 at 6:25 AM
playing one of the few Space Invaders ports for COSMAC ELF written in CDP1802 assembly, with no CHIP-8 interpreter.
it uses the PIXIE (CDP1861)’s highest available resolution mode, 64x128.
it uses the PIXIE (CDP1861)’s highest available resolution mode, 64x128.
Lee Hart from TMSI creates altoids-sized COSMAC computers, this is my 1802 membership card i have. it runs on a 4mhz CDP1802. it also comes with a ROM with monitor, RCA floating-point BASIC3, and Adventureland text adventure game.
January 6, 2026 at 7:48 AM
Lee Hart from TMSI creates altoids-sized COSMAC computers, this is my 1802 membership card i have. it runs on a 4mhz CDP1802. it also comes with a ROM with monitor, RCA floating-point BASIC3, and Adventureland text adventure game.
A little more retro computing. Ah... 16 universal 16-bit registers in an 8-bit CPU.
November 21, 2024 at 10:33 PM
A little more retro computing. Ah... 16 universal 16-bit registers in an 8-bit CPU.
Here's some more pin conditional jump (branch) instructions:
November 29, 2025 at 5:40 AM
Here's some more pin conditional jump (branch) instructions:
My CDP1802-equivalent RTL core can run at 166 Mhz in an XCKU5P Kintex Ultrascale+ FPGA (-1 speed grade). Given that my core takes exactly 1/8 as many clocks per instruction as a real CDP1802, this means that it will run at the equivalent speed of a 1.33 GHz CDP1802.
The real CDP1802 typically […]
The real CDP1802 typically […]
Original post on mastodon.social
mastodon.social
February 5, 2025 at 12:16 AM
My CDP1802-equivalent RTL core can run at 166 Mhz in an XCKU5P Kintex Ultrascale+ FPGA (-1 speed grade). Given that my core takes exactly 1/8 as many clocks per instruction as a real CDP1802, this means that it will run at the equivalent speed of a 1.33 GHz CDP1802.
The real CDP1802 typically […]
The real CDP1802 typically […]
Wow! I wish I still had my CDP1802 to check for old code.
January 13, 2025 at 10:27 PM
Wow! I wish I still had my CDP1802 to check for old code.
At VCF West I saw many vintage computers. In the 1970's I built a COSMAC ELF it used RCA's CDP1802 CPU. A fellow mentioned a currently available kit. It is called The 1802 Membership card. I ordered one kit and it arrived today. I completed the CPU board and started the front panel board.
August 16, 2025 at 12:39 AM
At VCF West I saw many vintage computers. In the 1970's I built a COSMAC ELF it used RCA's CDP1802 CPU. A fellow mentioned a currently available kit. It is called The 1802 Membership card. I ordered one kit and it arrived today. I completed the CPU board and started the front panel board.
Tom Pittman's “A Short Course in Programming” for the RCA 1802 as PDF and EPUB
#RetroComputing #CDP1802 #Cosmac #RCA #1802
#RetroComputing #CDP1802 #Cosmac #RCA #1802
Tom Pittman’s “A Short Course in Programming” for the RCA 1802
Tom's A Short Course In Programming (1980) is a good introduction for new 1802 programmers. Print copies are rare, so someone on the cosmacelf group asked if it existed as a printable PDF. Well, when you put it like that … Tom Pittman - A Short Course in Programming (97 pages, PDF, US Letter paper) Tom Pittman - A Short Course in Programming…
scruss.com
October 18, 2025 at 4:37 PM
Tom Pittman's “A Short Course in Programming” for the RCA 1802 as PDF and EPUB
#RetroComputing #CDP1802 #Cosmac #RCA #1802
#RetroComputing #CDP1802 #Cosmac #RCA #1802
Retro CPUs on the right will be placed on the ZIF socket on the left. The CPU boards have a serial EEPROM for ID.
The Cortex-M7 on the left identifies the CPU inserted and take care of the clock, memory and serial comm. The firmware is around 300kB including all assembler, disassembler, debugger.
The Cortex-M7 on the left identifies the CPU inserted and take care of the clock, memory and serial comm. The firmware is around 300kB including all assembler, disassembler, debugger.
June 4, 2025 at 4:27 AM
Retro CPUs on the right will be placed on the ZIF socket on the left. The CPU boards have a serial EEPROM for ID.
The Cortex-M7 on the left identifies the CPU inserted and take care of the clock, memory and serial comm. The firmware is around 300kB including all assembler, disassembler, debugger.
The Cortex-M7 on the left identifies the CPU inserted and take care of the clock, memory and serial comm. The firmware is around 300kB including all assembler, disassembler, debugger.
CDP1802: flexible 16x16 bit registers, clockable down to DC
Powerful instruction set, interrupts, CMOS efficiency
No wonder it was the brain of several space probes.
ELF-II plus KIM-1 pretty much did it all. Halcyon days.
#ComputationalThinking #GOFAI
Powerful instruction set, interrupts, CMOS efficiency
No wonder it was the brain of several space probes.
ELF-II plus KIM-1 pretty much did it all. Halcyon days.
#ComputationalThinking #GOFAI
August 31, 2026 at 5:18 PM
CDP1802: flexible 16x16 bit registers, clockable down to DC
Powerful instruction set, interrupts, CMOS efficiency
No wonder it was the brain of several space probes.
ELF-II plus KIM-1 pretty much did it all. Halcyon days.
#ComputationalThinking #GOFAI
Powerful instruction set, interrupts, CMOS efficiency
No wonder it was the brain of several space probes.
ELF-II plus KIM-1 pretty much did it all. Halcyon days.
#ComputationalThinking #GOFAI
1802 people mostly hang out at groups.io/g/cosmacelf
There's a very well maintained emulator for all 1802 systems (including the COMX) at www.emma02.hobby-site.com/index.html
There's a very well maintained emulator for all 1802 systems (including the COMX) at www.emma02.hobby-site.com/index.html
cosmacelf groups.io Group
The RCA CDP1802 COSMAC microprocessor was the basis for several hobbyist computers in the mid 70s and early 80s. Join this group to discuss these old computers or share your 1802 experiences.
groups.io
April 6, 2026 at 5:07 PM
1802 people mostly hang out at groups.io/g/cosmacelf
There's a very well maintained emulator for all 1802 systems (including the COMX) at www.emma02.hobby-site.com/index.html
There's a very well maintained emulator for all 1802 systems (including the COMX) at www.emma02.hobby-site.com/index.html
L'ordinateur mystère trouvé dans une valise...
l s'agit en fait d'un dérivé de l'ordinateur Elf, basé tout comme lui sur un microprocesseur RCA CDP1802. Il a été fabriqué en suivant les instructions d'un livre intitulé "Un microprocesseur pas à pas" et édité en 1981.
youtu.be/UGxTvFTYssc?...
l s'agit en fait d'un dérivé de l'ordinateur Elf, basé tout comme lui sur un microprocesseur RCA CDP1802. Il a été fabriqué en suivant les instructions d'un livre intitulé "Un microprocesseur pas à pas" et édité en 1981.
youtu.be/UGxTvFTYssc?...
January 29, 2024 at 5:46 PM
L'ordinateur mystère trouvé dans une valise...
l s'agit en fait d'un dérivé de l'ordinateur Elf, basé tout comme lui sur un microprocesseur RCA CDP1802. Il a été fabriqué en suivant les instructions d'un livre intitulé "Un microprocesseur pas à pas" et édité en 1981.
youtu.be/UGxTvFTYssc?...
l s'agit en fait d'un dérivé de l'ordinateur Elf, basé tout comme lui sur un microprocesseur RCA CDP1802. Il a été fabriqué en suivant les instructions d'un livre intitulé "Un microprocesseur pas à pas" et édité en 1981.
youtu.be/UGxTvFTYssc?...
VCF East- I attended Saturday, enjoyed Joyce Weisbeckers presentation on FRED and the RCA CDP1802. There was a fairly large turnout, I decided to leave before 2PM, wanted to avoid NYC bound traffic going home. I just read that there was a bomb scare there Sunday. Gladly it was just a sick persons.
April 20, 2026 at 3:03 PM
VCF East- I attended Saturday, enjoyed Joyce Weisbeckers presentation on FRED and the RCA CDP1802. There was a fairly large turnout, I decided to leave before 2PM, wanted to avoid NYC bound traffic going home. I just read that there was a bomb scare there Sunday. Gladly it was just a sick persons.
CDP1802 :)
November 29, 2025 at 5:53 AM
CDP1802 :)
Feed: "Adafruit Industries – Makers, hackers, artists, designers and engineers!"
By: Anne Barela on Monday, December 8, 2025
By: Anne Barela on Monday, December 8, 2025
Making a CHIP-8 emulator
Tobias V. Langhoff has written a guide to making a CHIP-8 emulator. CHIP-8 was created by RCA engineer Joe Weisbecker in 1977 for the COSMAC VIP microcomputer. It was intended as a simpler way to make small programs and games for the computer. Instead of using machine language for the VIP’s CDP1802 processor, you could […]
blog.adafruit.com
December 9, 2025 at 1:02 AM
Feed: "Adafruit Industries – Makers, hackers, artists, designers and engineers!"
By: Anne Barela on Monday, December 8, 2025
By: Anne Barela on Monday, December 8, 2025
But the actual path I took had to do with which microprocessors were the _least_ expensive. I had no money, and the choices under $25 were the RCA "COSMAC" CDP1802 and the MOS technology 6502.
April 8, 2026 at 2:15 AM
But the actual path I took had to do with which microprocessors were the _least_ expensive. I had no money, and the choices under $25 were the RCA "COSMAC" CDP1802 and the MOS technology 6502.
In 1976, I learned about the Intel 8085, Zilog Z80, Motorola 6800, MOS Technology 6502, and RCA CDP1802, and also about the Intel 3000 series and AMD Am2900 series bit-slice components.
Bit-slice really captured my imagination. Design your own processor! I wrote about my grand plans for that in […]
Bit-slice really captured my imagination. Design your own processor! I wrote about my grand plans for that in […]
Original post on mastodon.social
mastodon.social
April 8, 2026 at 1:01 AM
In 1976, I learned about the Intel 8085, Zilog Z80, Motorola 6800, MOS Technology 6502, and RCA CDP1802, and also about the Intel 3000 series and AMD Am2900 series bit-slice components.
Bit-slice really captured my imagination. Design your own processor! I wrote about my grand plans for that in […]
Bit-slice really captured my imagination. Design your own processor! I wrote about my grand plans for that in […]