Hobby computer

[Crypticalcode0]

I am contemplating building a hobby computer from spare parts i have lingering around.

So for a start 68K, 6502, Z80A, 8088.
I think i would use either a 68K or Z80 processor as main CPU since i have most of those CPU's

Which would be better as a main CPU?

 

[commodorejohn]

From a programming perspective, it's hard to beat the 68k line (especially if you have an 020 or 030.)

 

[barythrin]

Sorta depends how much experience you have as well. There is a large following for z80 SBC kits like the n8vem out there. Also lots of good books on making a homebrew computer with the 6502 though.

 

[Crypticalcode0]

I do electronics for a living.

Well if i use a 68K it does tend to give more flexibility to the design to some extend.
Okay then the Z80's shall be used as coprocessors.
What can be sped up using coprocessors?

 

[commodorejohn]

Sound and video are both natural candidates for coprocessor acceleration; you could use the Z80 as a poor man's GPU, or a multi-channel sound mixer. You could also do like the C64 did and offload disk access to a secondary CPU.

 

[Crypticalcode0]

That all sounds logical.

Let's see how far i can go.
I require either VGA or SCART compatible signals so Z80 as GPU is not done unless i use 3 one for each colour channel.
They would be required to run twice the pixel clock speed this is not a real option since i only have Z80A's...

Okay so that is where i would have to look into deeper.

Sound, let's say 48KHz this can be done with a Z80A so this is a good option.(68K Z80 combo, Arcade here i come!

Disk access could be done using a Z80 however this should so simple that using some F and HCT parts should do the trick.

 

[mnbvcxz]

If you were to build a computer based on the s100 bus, you could change processors by changing a board, also you could develop the system one board at a time, you might be able to buy used boards cheaply or buy new boards.

 

[RickNel]

If you were to build a computer based on the s100 bus, you could change processors by changing a board, also you could develop the system one board at a time, you might be able to buy used boards cheaply or buy new boards.

Have a look at John Monahan's s100computers.com site. They are building CPU boards using many different CPUs including 68*, plus many peripheral boards and combinations, all in TTL with the flexibility and transparency of the 100-pin bus. It's a smorgasbord, all non-commercial but plenty of expertise and experience on offer.

Rick

 

[Chuck(G)]

Good grief, if you do electronics for a living, why not design your own CPU architecture and implement it in an FPGA (or random logic if you're a masochist).

Or recreate one of the classics; how about CDC 6600 or IBM 7090?

 

[sprite9]

I'm currently building a Zeta-SBC Z80 single board computer so I can reccomend that unless you want to make your own pcb. As someone mentioned, the N8VEM site has several boards that use your cpus.

 

[patscc]

Crypticalcode0 said

I am contemplating building a hobby computer from spare parts i have lingering around.
So what other parts do you have laying around ? If you're going 68K, do you have the FPU, MMU, and some of the other various bits and bobs ? Is this a breadboard project, or will you be designing a PCB for it ?
patscc

 

[Chuck(G)]

Hey, Pat! Good to see that you're back!

 

[patscc]

Chuck(G) said

Hey, Pat! Good to see that you're back!

Thanks. I told myself I wouldn't touch anything vintage until I got a job in my field again. Didn't really think it was going to take this long, obviously.
patscc

 

[Crypticalcode0]

If you were to build a computer based on the s100 bus, you could change processors by changing a board, also you could develop the system one board at a time, you might be able to buy used boards cheaply or buy new boards.

I probably could but the S-100 bus would most likely end up being the bottle neck in my design then....

Good grief, if you do electronics for a living, why not design your own CPU architecture and implement it in an FPGA (or random logic if you're a masochist).

Or recreate one of the classics; how about CDC 6600 or IBM 7090?

As my alias implies i am good at making code look like a mess.
Besides if i would do such a thing i would end up with a 68K compatible and drop some of it's instructions most likely.

I'm currently building a Zeta-SBC Z80 single board computer so I can reccomend that unless you want to make your own pcb. As someone mentioned, the N8VEM site has several boards that use your cpus.

Now what is the fun in buying a PCB board, or using someone else's design?
It's easier and it is good reference, but each design is based on requirement/choices and mine do not need to be the same.

I am contemplating building a hobby computer from spare parts i have lingering around.
So what other parts do you have laying around ? If you're going 68K, do you have the FPU, MMU, and some of the other various bits and bobs ? Is this a breadboard project, or will you be designing a PCB for it ?
patscc

MC68882FN33, but more importantly I have a PRM for that family of processors, the User's manual and the family reference manual.
Knowledge is more important then anything, and besides that I know my way around the 74Logic family.

 

[Chuck(G)]

You know, an interesting and oft-overlooked CPU family was the NSC 32K line (32016, 32032...). Not designed at NSC, but a remarkable CPU all the same. Far ahead of anything

The WikiP article has the date for the availability of the 16032 wrong, however. It was announced about 1979, but real silicon never made it out until about 1982-83. National evidently had a heckuva time building it. One of my monthly chores starting in about 1980 was calling NSC and asking their marketing people if it was soup yet.

It's far more advanced than the 68K. Take a look at the PC532 here.

 

[patscc]

Didn't they also put out a castrated version, the 32008, kinda like a 68008 ? I seem to remember wanting a kit based on it when I was a kid.
patscc

 

[Crypticalcode0]

@patcc yes they did.

@Chuck Like i said in my first post spare parts lingering around.
If i truly were masochistic I would use 2650A's.

 

[Crypticalcode0]

I have found several simm 72 sockets in the connector drawers It seems they are begging to be used.
Hm, does anyone know how the CAS and RAS on these work I seem to vaguely recall something special about CAS but do not remember what it was.

 

[Chuck(G)]

@patcc yes they did.

@Chuck Like i said in my first post spare parts lingering around.
If i truly were masochistic I would use 2650A's.

I picked up a 32016 (PLCC) from an old Panasonic laser printer. Maybe you can find one. Old laser printers have lots of great parts in them.

 

[Crypticalcode0]

last one i opened had a 68K in it.

old laser printers indeed have good parts in them.