Purchasing vintage CPUs

[Richardcavell]

Hi, all. Sorry for the random questions but I am a self-taught electronics enthusiast.

Is it possible to buy any of the following microprocessors any more? (Including, obviously, clones or derivatives that will run unmodified code): 6502, 6809, 68000 including 680x0, 8086, 80286.

TIA,

Richard

 

[Inquisitive]

Hi Richard,

A quick search at Jameco in Belmont, CA. I found a 6502 still for sale. Have not had a chance to go through your shopping list. Have not had chance to check ebay or other sources.

Not sure if that would be cost effective for you as you have not stated where in the world you live.

Inq

 

[absf]

I just bought some 65C02 from ebay 2 months ago. They are the 10MHz CMOS version as compared to the generic 1MHz one used in Apple II. You can also find 1802 clones but not the original RCA ones on ebay.

**broken link removed**
**broken link removed**

For 6809, I have a few 68B09 removed from outdated PCB from my workplace. But if you do some googling, you should be able to find them from eBay or electronics stores like electronic gold mine or Arrow or Jemeco.

You did not say what you wanted them for. Are you going to make computers out of them ot just for collection?

Allen

 

[Ian Rogers]

You can get the RCA1802 on ebay.... This was similar to the 6502..

 

[Wade Hassler]

You can get the RCA1802 on ebay.... This was similar to the 6502..

I disagree. The 1802 was brain-breakingly different from the Motorola/Mostek CPUs
Here's a picture

 

[granddad]

I <3 the RCA 1802 , made a board for it , had a 5 1/4 disk operating system 2k in 2716 eeprom. booted from battery backed cmos , is my collection of old cpus worth anything ?

 

[Mike - K8LH]

Hi, all. Sorry for the random questions but I am a self-taught electronics enthusiast.

Is it possible to buy any of the following microprocessors any more? (Including, obviously, clones or derivatives that will run unmodified code): 6502, 6809, 68000 including 680x0, 8086, 80286.

Hi Richard.

I've purchased a couple Harris CDP1802 devices, a few Rockwell R65C02 (4-MHz) devices, and a pair of HD63C09P devices (a higher speed 6809 with enhanced instruction set) from Chinese vendors on ebay without any problems. All are NOS (New Old Stock). You should be able to find the other CPUs there, too.

I had a lot of fun building a miniature 3-chip 1-MHz 65C02 system awhile back with 64K RAM and BASIC (see below).

Good luck. Have fun.

Cheerful regards, Mike

 

[Ian Rogers]

I disagree. The 1802 was brain-breakingly different from the Motorola/Mostek CPUs
Here's a picture

My appologies... We used to use the RCA 1802 in one of our older designs and the guy who originally designed the circuit used the BBC micro to develop the system. He said he used the RCA 1802 as it was similar to programming the 6502... I took it as read!!! I never doubted him....

 

[atferrari]

My appologies... We used to use the RCA 1802 in one of our older designs and the guy who originally designed the circuit used the BBC micro to develop the system. He said he used the RCA 1802 as it was similar to programming the 6502... I took it as read!!! I never doubted him....

I always believed that the COSMAC 1802 predated the 6502; just checked and it is the opposite. The 1802 was the first one I read about used in a project. Radio Electronics or ...?

I wonder if there is any spacecraft sporting a 1802 still alive, out there...

 

[absf]

Hi Richard.

I've purchased a couple Harris CDP1802 devices, a few Rockwell R65C02 (4-MHz) devices, and a pair of HD63C09P devices (a higher speed 6809 with enhanced instruction set) from Chinese vendors on ebay without any problems. All are NOS (New Old Stock). You should be able to find the other CPUs there, too.

I had a lot of fun building a miniature 3-chip 1-MHz 65C02 system awhile back with 64K RAM and BASIC (see below).

Good luck. Have fun.

Cheerful regards, Mike

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Wow, that's really fantastic. What is the job of the 18F pic besides being a UART for communicating with PC? Where is the monitor program, Basic interpreter and character generator resided in?

I recognized that it is the same Basic used in my OSI C1P single board computer. Was it an open sourced project or was it made for sale (with PCB)? I am really interested to build one too just for nostalgic purpose.

Allen

 

[KeepItSimpleStupid]

I did the code for a model gantry crane using the 1802. All hand compiled. The first thing I wrote was way to "call subroutines". There was no such instruction. Just "Pass the program counter". I used the Radio Electronics system.
I still have the subroutine code on "paper".

Later, I did it again in an interpreted BASIC on the VitraxIX SBC (Single Board Computer) with better gantry (sliders), Potentiometer limit based feedback for the crane) and the loading docked stopped before the pins (needed an extra port for that).

The 4004 pre-dates the 8008. I believe the 4004 was used in calculators Between the 8008, Z80, for me the assembly language was non-intuitive and it wasn't standardized compared to say a 6800.

 

[Mike - K8LH]

Wow, that's really fantastic. What is the job of the 18F pic besides being a UART for communicating with PC? Where is the monitor program, Basic interpreter and character generator resided in?

Hi absf. Thank you for the kind words.

The PIC provides the conditioned 'reset' and the 1-MHz CPU clock signals. During power-up or reset it provides a "blind loader" function. That is, it "pushes" instructions to the 65C02 over the data bus and the 65C02 copies the monitor program and BASIC from PIC Flash memory to 65C02 RAM memory at $E000..$FFFF. The PIC also includes a soft address decoder function that uses a 256 byte decoder map table to map the 'CSx' chip select pins into 65C02 address space (with single page resolution). I mapped the PIC18F26K22 Special Function Registers located at $0F00..$0FFF in PIC data memory into 65C02 address space at $DF00..$DFFF. Basically, the 65C02 has direct access to all 230 PIC SFRs though I only use the SFRs associated with the PIC Serial and SPI peripherals. I can download a new decoder map into PIC flash memory at any time to add a 65C22 or similar devices into the memory map or to change the memory map to mimic retro computers like the KIM-1.

I recognized that it is the same Basic used in my OSI C1P single board computer. Was it an open sourced project or was it made for sale (with PCB)? I am really interested to build one too just for nostalgic purpose.

Allen

It's just a personal project and not "open source" at this time. If there is enough interest I would consider making some boards and offering one or more kits for sale. The design is expandable (see below) and I'm considering adding a PIC32MX for keyboard & video (vga).

My apologies for hi-jacking the thread.

Cheerful regards, Mike

 

[Mike - K8LH]

I did the code for a model gantry crane using the 1802. All hand compiled. The first thing I wrote was way to "call subroutines". There was no such instruction. Just "Pass the program counter". I used the Radio Electronics system.
I still have the subroutine code on "paper".

It's a very interesting device and architecture which I had never had a chance to play with. I studied and verified its control signals by clocking it 1/2 cycle at a time through each "machine cycle" using a PIC.

Based in part on that research I built a couple different two chip serial systems but I'm still struggling with the instruction set.

 

[ronsimpson]

There was talk about the RCA CDP1802. Look what I have.

Also in this pile:
6800, 8085, 68B00, MC146805, MK3874, 8039, 8074, 8748, 8048,
What I went looking for was a prototype 8088. Did not find it. (hand assembled, 8088 written in pencil) It looks much like the 8748 white ceramic.
----edited----
Just looked on ebay. Some one thinks they are going to get $50.00 us for an RCA 1802. lol Should put some up for $30.00.

I probably payed $100.00 for the MK3874 back in 1978.
Probably the C8751-8 was $50.00. That bought a lot of fuel for the car back then.

 

[Mike - K8LH]

Wow! Ceramic packages and gold pins...

 

[KeepItSimpleStupid]

1802 in Space: https://www.retrotechnology.com/memship/1802_spacecraft.html

 

[Richardcavell]

I just bought some 65C02 from ebay 2 months ago. They are the 10MHz CMOS version as compared to the generic 1MHz one used in Apple II. You can also find 1802 clones but not the original RCA ones on ebay.

**broken link removed**
**broken link removed**

For 6809, I have a few 68B09 removed from outdated PCB from my workplace. But if you do some googling, you should be able to find them from eBay or electronics stores like electronic gold mine or Arrow or Jemeco.

You did not say what you wanted them for. Are you going to make computers out of them ot just for collection?

Allen

Allen,

I want to make my own 8-bit computer. The market might have moved on but I haven't.

I have used the current Atmel AVR 8-bit microcontrollers, but they have their own flash and RAM on the same chip. That's cheating. I don't think I should get any credit for turning one of those into a standalone computer.

Richard

 

[Richardcavell]

Hi Richard.

I've purchased a couple Harris CDP1802 devices, a few Rockwell R65C02 (4-MHz) devices, and a pair of HD63C09P devices (a higher speed 6809 with enhanced instruction set) from Chinese vendors on ebay without any problems. All are NOS (New Old Stock). You should be able to find the other CPUs there, too.

I had a lot of fun building a miniature 3-chip 1-MHz 65C02 system awhile back with 64K RAM and BASIC (see below).

Good luck. Have fun.

Cheerful regards, Mike

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That's an impressive bit of engineering, Mike. I like your neatly laid out PCB.

The old 8-bit machines had ROM chips that would contain an operating system (or at least a minimal one) and a BASIC interpreter, etc. I see you're using a PIC chip to store and deliver the ROM. But that's modern technology. What would be the modern equivalent of a ROM? Is it possible to compile code for a 6809 and store it in a FLASH or EEPROM that has an 8-bit bus and then let the 6809 access it?

If you were to memory map the ROM so that it only takes up part of the address space, how do you differentiate between memory addresses that should go to the ROM and addresses that should go to the RAM chip?

Richard

 

[Mike - K8LH]

What would be the modern equivalent of a ROM?

Many people still use ROM. Many use 8K (28C64) or 32K (28C256) EEPROM which doesn't require special programming voltages. Plenty of NOS available on ebay and from other various vendors. More and more of us are designing romless boards and using a small uC as a "blind loader" to copy a ROM image into RAM at start-up, effectively replacing "slow" ROM or EEPROM in favor of "fast" RAM.

Is it possible to compile code for a 6809 and store it in a FLASH or EEPROM that has an 8-bit bus and then let the 6809 access it?

There are probably several ways to do that. An SD card file storage system might be nice...

Since you're interested in 6809, check out Grant Searle's Simple 6809 design. Grant provides ROM files that include a simple Monitor & BASIC.

If you were to memory map the ROM so that it only takes up part of the address space, how do you differentiate between memory addresses that should go to the ROM and addresses that should go to the RAM chip?

You would use an address decoder. You might want to check out Garth Wilson's 6502 Primer, if you haven't already, which includes a section on address decoding. You'll see people using everything from a simple 74HC00 or 74HC139 decoding large 16K blocks to PAL/GAL/CPLD devices decoding much smaller blocks.

I see you're using a PIC chip to store and deliver the ROM. But that's modern technology.

Yes, it's a compromise of sorts. I will only use through hole parts. No PALs or GALs. No CPLDs or FPGAs. However, I don't have a problem using a PIC. The PIC uses much less PCB real-estate by replacing a bunch of discrete logic and it provides much more capability while it presents to the 65C02 as classic I/O.

Have fun.

Cheerful regards, Mike

 

[KeepItSimpleStupid]

I, sort, of made a microcoded computer as part of a team of 3 in a University lab course. It had 16 words of 16 bits of I-space and 16 4 bit words in D-space and could sort numbers in ascending or descending order. All parts were TTL. Three major parts program counter/branching: me, memory, and some data selectors/compares. I KNOW why the PC counter has to point to the next instruction.