Z80

[xlar54]

Even though the Z80 is there primarily for CPM, I wonder sometimes what else can be run using that processor. Anyone know if it is capable of running homebrew or other OSes?  I think the Z80 was WAY overlooked by the Commodore community, and most people saw it as Z80 = CPM.

[Guest]

I think any alternative OS for the Z80 will suffer the same performance penalty that CP/M suffers on the 128 platform.

[Blacklord]

I think any alternative OS for the Z80 will suffer the same performance penalty that CP/M suffers on the 128 platform.

What about as a basis for say a Speccy emulator ?

Lance

[Guest]

What about as a basis for say a Speccy emulator ?

Why???

Well, on a flat 128 it wouldn't be toooo alien as a doorstop emulator.

[Blacklord]

What about as a basis for say a Speccy emulator ?

Why???

Well, on a flat 128 it wouldn't be toooo alien as a doorstop emulator.

Ok ZX80 or ZX81 emulator then, with rubber keyboard overlay

[Hideki]

Hihi

There was a Sinclair Simulator for the C64, that allowed you to write spectrum basic programs, obviously machine code wasn't available

I don't think an emulator on the C128 is viable unless you can allocate 64K to the Z80, 64K to the 6510 (sorry, can never remember the number of the new one), load the spectrum/zx81/jupiter ace/zx80 ROM into the bottom 16/8/8/4K of memory and execute it there, using the commodore CPU to handle the I/O, screen etc... bear in mind the spectrum keyboard is read as 5 half rows of keys on each of 8 ports, that might require some extra interfacing (or patching of the ROM to read from the C64 keyboard but that'd break a lot of games)

but I'm rambling, basically, if you can use both CPUs at once with their own memory

You'd also need to somehow switch off the 80 column hardware because I'm told that slows down the Z80 to about 2MHz which is too slow for spectrum stuff (although fast enough for 80/81/ace)

I do tend to think if it could have been done it would have been though, it might even be possible to run small gameboy games on it somehow but I don't know enough about the hardware to say really, I could do with a reference manual -.-

[Blacklord]

You'd also need to somehow switch off the 80 column hardware because I'm told that slows down the Z80 to about 2MHz which is too slow for spectrum stuff (although fast enough for 80/81/ace)

(I moved this topic into a more suitable area!)

Does the Z80 in the C128 run at 4MHz initially & then slow down ?

Lance

[Hideki]

Hihi

Yes, I'm fairly sure the CPU runs at either 4 or 3.5MHz but is slowed down to an effective speed of around 2MHz because it's sharing time with the 80 column hardware -.-

I've not actually opened up the machine and had a look but I will :|

[adric22]

I had some interest in the Z80 back in the 1980's.  I really wanted to write code for it, but just couldn't find any compilers or even an ML monitor for it.   I did eventually write one small Z80 program.. I mean, really small.  All it did was flash the border or something of that nature, as I recall.  I had to write it in "pure" machine language by looking at a book I found at the library on Z80 machine code.  I literally had to POKE the values for the different commands and stuff into the right place in memory, then switch over control to the Z80.   I can see why nobody used it, it was a huge pain to program for due to lack of tools and documentation from Commodore.  

I've had people tell me that the Z80 was bad on the C128 because of the way in which is was implimented made it slower than the 8510.  However, I'm not sure that is 100% true.  Because if i remember, the Z80 could handle 16-bit calculations which would have made a lot of software run much faster.  I think I/O access was handled by the 8510, if I recall.

Can VICE run the 128 in CP/M mode?  I've never tried.

[TomL_12953]

Can VICE run the 128 in CP/M mode?  I've never tried.

Yes, VICE does run the CP/M .d64 images available.

Tom Lake

[airship]

The problem is that the 8510 does all the I/O for the Z80 - video, keyboard, etc. So the Z80 runs at 2.1 MHz, just like the 8510. There is simply no way around this. Parts of the CP/M BIOS are written in 6502 code!

[dilbert]

Even though the Z80 is there primarily for CPM, I wonder sometimes what else can be run using that processor. Anyone know if it is capable of running homebrew or other OSes?  I think the Z80 was WAY overlooked by the Commodore community, and most people saw it as Z80 = CPM.

new kid on the block:

one of your members kindly routed me here. this is my debue post.

I found this article in the Trasnactor:  RE:Z80 and 8502http://cbm.csbruce.com/~csbruce/cbm/transactor/v7/i3/p048.html

I'm looking for ways to use the Z80 to as I just got my C128s this year but am a past z80 fan (trash 80 & Timex Sinclar):stolt:

[xlar54]

Well, welcome dlibert.  I think you'll find the community here to be very good.  Z80's arent the primary focus, but the 128's alter ego is something we poke at from time to time.

[dilbert]

Well, welcome dlibert.  I think you'll find the community here to be very good.  Z80's arent the primary focus, but the 128's alter ego is something we poke at from time to time.

thank you.

 Yes i'm here on the fourm for C128 info and rants too. Got invited by one of your members. :-)

[XmikeX]

Tangentially related to the thread here, an interesting Z80/C128 thread on usenet : http://groups.google.com/group/comp.sys.cbm/browse_thread/thread/60e46cab6bb731f5/bec3d794a00567fa?hl=en&

- end summary here : http://groups.google.com/group/comp.sys.cbm/browse_thread/thread/712680742367b2fc/f7c66d120e620e?hl=en&q=#00f7c66d120e620e

At the moment, I can find no further record of the OP's progress beyond 2004.
Unfortunately, the OP (Sven Paepke) seems to have died in a diving accident in 2007.

XmX