I want to make my own CPC 8bit

[TFM]

Perhaps it was too much to build an 8088 based computer and Incorporate CPC components in with it. Might have been interesting had it happened given GEM has become another Open Source program with the possibilities of adding Internet support to it.

The 8088 - like the Z80 - has a 8 bit data bus. There is no gain in using that crap instead of a Z80, but it would bring 100% imcompatibility to previous machines.

But there would be a gain in using a 16 MHz / 20 MHz Z80 with an option of slowing down to 4 MHz. (Take a look at the PCW 16 - great machine).

[Ygdrazil]

I agree with TFM, the advantage of using a 8088 is marginal, only thing that springs into mind is the segmented memory model..

/ygdrazil

The 8088 - like the Z80 - has a 8 bit data bus. There is no gain in using that crap instead of a Z80, but it would bring 100% imcompatibility to previous machines.

But there would be a gain in using a 16 MHz / 20 MHz Z80 with an option of slowing down to 4 MHz. (Take a look at the PCW 16 - great machine).

[AMSDOS]

So you're saying the Z80 is Crap? Perhaps I'm thinking of the 8086 processor! Er yeah sorry, I meant 8086! 

[AMSDOS]

Of course I was only talking hypotetically since Amstrad had invested interest in IBM Based computers. Perhaps the closest thing Amstrad up with was an Amstrad PC-20 which sort of looks like a CPC Plus - made to compete with the likes of Amigas. It's processor was 8086 based I think (it came out around the same time as the CPC Plus'), might have been interesting to see what sort of machine it might have been like had it had an CPC Intergrated into it! 

[steve]

I think Amstrad made the MegaPC which combined a PC and a Megadrive in one unit, so having a PC+CPC would be seen as a step backwards.
I would have like the later PCW models to be compatible with CPC software , using a built in colour monitor obviously.

[TFM]

So you're saying the Z80 is Crap? Perhaps I'm thinking of the 8086 processor! Er yeah sorry, I meant 8086! 

No you dont get it    The Z80 is great, but the 8088 is crap.

And honestly the 8086 is crap too, the only difference to the 8088 is, that it has a 16 bit data bus. But already the HD64180 =(roughly)= Z180 has more power. It beats the 8086 into ground, its multiplication only needs 17 cycles!!!

Amstrad should have taken the Z280, but Zilog has this one too long in the drawer.

Take a look at the cpu's data sheets.

[steve]

The latest chip is the eZ80 running at up to 50mhz and executing one instruction per clock cycle makes it equivalent to a z80 running at 200mhz.
The eZ80 can address 16MB memory using either 16 or 24bit addresses.

[TFM]

The latest chip is the eZ80 running at up to 50mhz and executing one instruction per clock cycle makes it equivalent to a z80 running at 200mhz.
The eZ80 can address 16MB memory using either 16 or 24bit addresses.

Aside it's problem with 16 bit I/O this is still the cpu of choice, since the Z180 doesn't support all undocumented Z80 opcodes (some game... some C libraries etc.), and the Z280 is a bit buggy (and not produced any longer!!!).

Are you sure they _sell_ it now with 50 MHz, thought actually only 25 MHz?

However, if you want to use it for a CPC compatible hardware, then you must catch and emulate the I/O instructions, since the eZ80 has 8 bit I/O 

[redbox]

The latest chip is the eZ80 running at up to 50mhz and executing one instruction per clock cycle makes it equivalent to a z80 running at 200mhz.
The eZ80 can address 16MB memory using either 16 or 24bit addresses.

This reassures me that I'm not wasting my life programming the Z80.   

[TFM]

This reassures me that I'm not wasting my life programming the Z80.   

You gotta tell it Richard ;-)

[AMSDOS]

And yet the majority of machines today are based on 8086/8088 technologies!   

And you still haven't justifying your reasoning as to how a 8088 & 8086 are crap over a z80!    8088 is 16bit with an 8bit data port as you pointed it - still it's 16bit processor & 8086 is 16bit through and through, they offer memory segments allowing up to 1mb of memory accessed.  Amstrad had an interest in these technologies and were producing machines with those technologies around the time the CPC Plus was released in 1990. All I'm merely saying is it would have been interested to see what kind of machine it would have been like had Amstrad machine a machine which integrated the low-end PC with a CPC Plus. Suddenly everyone would have a machine which could have the Internet, true a 16bit Z8000 based processor would most likely allow that as well, though if you put timeline into context in 1990 PCs were pushing forward in being the dominant processor, perhaps a Z8000 based processor would be able to do similar stuff, though the biggest setback for them processors is software!

[Ygdrazil]

 
Hi CP/M user

I did not mean that the 8088/8086 processors are crap!! I just think that using them to make a new CPC would be like reinventing the PC or making a crossover between an XT and CPC (Not making a new CPC but a completely new computer).

Historically though it would have been very interesting to see how the world would have been if Amstrad did go 16bit home computer wise!

Very few home computers did use 8088/8086 processors I know of only one(Strange there must be a reason): the Spectravideo SVI838.

http://www.samdal.com/svi838.htm

I think that if Amstrad had chosen to use a 8086 it would have been done something like the SVI838, to maintain CPC compatibility! (a PC1512/CPC6128(+))  In the end Amstrad did actually use an approach similar to the SVI838: http://www.cpcwiki.eu/index.php/File:Amstrad_Mega.jpg

Personally I would have preferred to use the Z8000 processor instead (everybody else used Motorola/Intel 16bit). Commodore actually did try to create a Workstation based on the Z8000 (Codename: Commodore 464 ), but apparently the Z8000 was way to advanced for Commodore to make it work
http://www.floodgap.com/retrobits/ckb/secret/900.html



If Amstrad should have launched a 16bit home computer it should have been around 1985 or so(at the same time as the ST  and Amiga), and when CPC compatibility was not essential.
By 1990 it was to late to launch a completely new platform.

Well thats just my opinion!

/Ygdrazil

And yet the majority of machines today are based on 8086/8088 technologies!   

And you still haven't justifying your reasoning as to how a 8088 & 8086 are crap over a z80!    8088 is 16bit with an 8bit data port as you pointed it - still it's 16bit processor & 8086 is 16bit through and through, they offer memory segments allowing up to 1mb of memory accessed.  Amstrad had an interest in these technologies and were producing machines with those technologies around the time the CPC Plus was released in 1990. All I'm merely saying is it would have been interested to see what kind of machine it would have been like had Amstrad machine a machine which integrated the low-end PC with a CPC Plus. Suddenly everyone would have a machine which could have the Internet, true a 16bit Z8000 based processor would most likely allow that as well, though if you put timeline into context in 1990 PCs were pushing forward in being the dominant processor, perhaps a Z8000 based processor would be able to do similar stuff, though the biggest setback for them processors is software!

[steve]

Are you sure they _sell_ it now with 50 MHz, thought actually only 25 MHz?

Had a quick glance at the Zilog website, there are several members of the eZ80 family, 1 runs at 20mhz but at least 2 others run at 50mhz, although they are probably speed rated so you may have the choice of using a slower chip if you had to.

[steve]

There is even, or was, the Z380 which was a 32 bit version of the z80 and which can/could address 4GB ram, but how could such a large address space be used in a home computer?, of course, graphics could take up hundreds of megabytes, but not 4 Gigabytes surely?

A 32 bit CPC would not be doing the commercial work that the PC is designed for, so how much memory would be considered to be sufficient for the tasks it would be used for in the home?

[Bryce]

Hi All,
      I've been reading down through this thread and I am seriously confused. I know we all like the Z80 here and it was a great processor for its time, but why on earth would Amstrad have wanted to stretch the life of the Z80 at all? It wasn't theirs to promote and there's absolutely no commercial reason to do so. They brought out the PC 1512 / 1640 which were 8086 based machines for many very good reasons. The Z80 hadn't kept up with things, it was dated, limited  and relatively expensive. Keeping compatibility with the 6128 would have had priority No. 5 Zillion. The the other contending 8 bits were going the same way, the Motorola 68xx was already dead in the water and the MOS 65xx days were numbered. Amstrad were left with 2 choices: Go with the 68000 as chosen for the ST and Amiga or go with the 8086. The 8086 had a better architecture, was cheaper and had much more support (including reference hardware designs, which meant that they didn't even have to the design the hardware from scratch). It was a no-brainer. ST and Amiga also weren't worried about backwards compatibility (why let people use old outdated software when they can buy new shiny versions) and Amstrad had already learnt that a computer is only as good as the software on offer for it. So with the IBM-Clone boom just starting, Amstrad knew that the software side was sorted, that home computers as we knew them were dead and that selling PC to home computer owners meant keeping the price low (ie: forget any backwards compatibility). Emotions and nostalgic reminiscance aren't things that happen in the commercial world.

Bryce.

[steve]

@Bryce, that is a different question entirely, we know and understand the commercial reasons why Amstrad abandoned the CPC, this thread was about one persons desire to build a new CPC which evolved into a discussion on alternative processors which would be faster than the admittedly outdated Z80.

It probably won't happen, but I still like to imagine what might be possible, there is the NatAmi project which is developing a modern Amiga compatible computer in an FPGA, even though the 68k line is no longer being developed, the NatAmi team have designed a 68k compatible processor that is 2-3 times faster then a 66mhz 68060, giving the NatAmi a nice speed advantage over any of the old amigas that are still working.

It might be an interesting project for someone who knows how to program FPGAs, to buy a NatAmi and reprogram it to create a new PLUS compatible computer which could be 150 times faster and have much better graphics and sound, but that too is unlikely to happen.

[steve]

The 8088/8086 was not much better than the z80, it only became dominant because IBM chose it for their PC's ( they did not want the PC to take sales from their minicomputer business, so the PC was deliberately underpowered, the 68000 would have been a much better choice), if IBM had not launched the PC, we would probably have seen the 68000 developed to multi-core and 64/128bits by now.

[Bryce]

True, but that's the way the industry works, if the best choice always won, we'd have watched Betamax videos during the 80s and 90s and probably be viewing HD-DVDs today instead of BlueRay.

Bryce.

[Cpcmaniaco]

Do you Know this? :

http://mcc-home.com/

A curiosity thing with 3 cores on the FPGA now.

http://mcc-home.com/4.html

[TFM]

True, but that's the way the industry works, if the best choice always won, we'd have watched Betamax videos during the 80s and 90s and probably be viewing HD-DVDs today instead of BlueRay.

Bryce.

What's bad about Blue Rays? The can take up to 50 GB an I burn them since 2 years without a dropout. Great media IMHO:
But, yes right, the industrial standard was never (or if, then only very seldomly) the "best choice".

@all:

About CPC Clones, we have/had three of them:
- C-One (running CPC core)
- T-Rex-1
- CPCng (never more than a bunch of ideas)

So what does this mean? Well, if you want a CPC clone, so get a FPGA board and use this as hardware. VHDL emulations of Z80, CRTC, PPI, etc... are available without a problem (contact Tobiflex who created the T-Rex1 core and the CPC core for the C-One). Maybe it's time for someting new ;-)

[AMSDOS]

Ygdrazil wrote:

I did not mean that the 8088/8086 processors are crap!! I just think that using them to make a new CPC would be like reinventing the PC or making a crossover between an XT and CPC (Not making a new CPC but a completely new computer).

Well everyone has their own opinions and thoughts about them, which I'm happy to leave it at that.

Historically though it would have been very interesting to see how the world would have been if Amstrad did go 16bit home computer wise!

I think they tried to do this with their PC-20 computer, everything about the design of that machine has Amiga written on it (I've attached a fuzzy picture of one). This had an 8086 processor, though by the time it was released, Amiga's were ahead on graphics & price - I think this machine was sold he in Oz for $900. The PC-20 came with CGA which was way behind the 8 ball in the late 80s early 90s! So I'm guessing a PC-20 is a rare computer to find these days given it was just about doomed the moment it was released. 

Very few home computers did use 8088/8086 processors I know of only one(Strange there must be a reason): the Spectravideo SVI838.

IBMs followup computer to their PC is considered a Home Computer, in 1983 (before or after XTs had arrived I'm not sure) they released a PC Jnr, which has a 8088 processor running at 4.77Mhz, can be expanded upto 640Kb. This machine seems to have a popular following because fans of it seperate it from IBM compatables.  Another simular looking line of machines made from Sanyo are MBC-550 and MBC-555 - this site describes them as IBM Compatables, though looking at the spifications of it, appears to be a system in it's own right. First clone of an IBM perhaps sounds correct, though would put my money on it being compatable since it runs slower than an PC. This system had it's own specific version of MS-DOS and had it's own BASIC, though after reading a bit about this system, it sounds like a machine designed for Serious applications!


I think that if Amstrad had chosen to use a 8086 it would have been done something like the SVI838, to maintain CPC compatibility! (a PC1512/CPC6128(+))  In the end Amstrad did actually use an approach similar to the SVI838: http://www.cpcwiki.eu/index.php/File:Amstrad_Mega.jpg

I'm familair with that one - didn't they have two - one with a 386 and the other with a 486 processor, both with a Sega Mega drive built-into the side of it. I'm thinking those machines came out around 1992 or 1993, by that time 386s and 486s were popular, Windows 3.1 had arrived to replace the dodgy Windows 3.0 from 1990.

Personally I would have preferred to use the Z8000 processor instead (everybody else used Motorola/Intel 16bit). Commodore actually did try to create a Workstation based on the Z8000 (Codename: Commodore 464 ), but apparently the Z8000 was way to advanced for Commodore to make it work

Well I obviously don't know a great deal about this, though since Zilog made Z80 which is an Enhanced Processor based from Intel's 8080, I'm presuming a Z8000 and successive processors are Enhanced versions of Intels processors?


If Amstrad should have launched a 16bit home computer it should have been around 1985 or so(at the same time as the ST  and Amiga), and when CPC compatibility was not essential.
By 1990 it was to late to launch a completely new platform.

Possibly, though 16bit technology was still quite expensive around the mid-80s, might have been using a Spectrum or C64 if things were like that. 

Bryce has summed up my thoughts quite well. Though everyone has different ideas about this, I was merely trying to picture and place everything based on what they had done in successive years after the original CPCs and picture what they should have done when they released the CPC Plus machines. I'm not personally criticising those machines and they do setout what Amstrad wanted I believe, and perhaps my views are wrong - 8088/8086 was perhaps at it's peak in the late 80s, though with the arrival of Windows 3.0 around 1990, those processors weren't really meant for it and even my friends 286 wasn't the best processor for it, Windows 3.1 came out around 1992 and was an improvement on that and far more stable, by then 386s were being used. Those processors are really cut-throat in terms of their lifecycle - which seemed to be a couple of years, by 1995 it was recommended you had a 486 with 8Mb of RAM! And so on.

Amstrad perhaps could have done their own thing and made a machine Intergrating 8086 technologies and incorporating their CPC Plus into that, making a machine which could handle GEM and a range of Applications, from the stuff they had from PCs and somehow Intergrating into the CPC Part. Use of ROM perhaps & RAM Disk, 3.5" & 3" Disk Drives! 

All just ideas of course, though I guess if anyone wanted to look into this to see what's possible - I'm certainally more than happy to see those theories blown out of the water! Wonder if Cliff Lawson would know? 

[Amstari]

CP/M User, it's interesting that you mentioned both the PC Jnr and PC20 in your last post.

My high school had a class room with several PC Jnrs. One of my electives subjects was "computer studies" which was really just all the kids playing computer games while the teacher did nothing. The only games I can remember are Tomcat and Buck Rogers.

Then they replaced all the PC Jnrs with Amstrad PC20s with monochrome monitors. I only ever used them for word processing with Wordstar.

.... sorry went off-topic but it brought back some memories!

[CPCOxygen]

Regarding the orginal post,

A CPC clone could be build around a Microcontroller such as the Parallax Propeller ( http://en.wikipedia.org/wiki/Parallax_Propeller ). I'm not very good when it come to electronics but I am working on a small computer based on this cheap (about 8 Euro) powerful   microcontroller, so easy as it has build in video and ram - basically it's one level up from soldering LEDs!
 
I'm thinking along the lines of a Z80 CPU with the microcontroller handling video output, audio, input, output, ROMS etc etc

On the parallax forum (http://www.parallax.com ) there are people who build Z80 based CP/M machines.

Think of the possibilities, a CPC clone that can connect to a VGA screen, SD card access etc. The Propeller is a 32bit microcontroller with 8 cores operating at 100 MHz - 20 MIPS for each core so it certainly has the horsepower with or without a real Z80 attached - the whole thing could be run within the chip and one EPROM.

It would be an interesting project for sure.

Building the hardware, without a real Z80 = very easy - I can do this. But emulating the CPC on the propeller I would find difficult but anyone who could write any type of CPC emulator could do it - I would even build the hardware and send it to them to make the emulator.

Building the hardware with a real Z80 = somewhat more difficult - would require help or luck. ROMs could be stored on one EPROM (actually the EPROM that used to boot the propeller chip could be used for the CPC ROMs also), got to make sure video and audio and all inputs and out put behave like a real CPC to have 100% compatibility.



Spectrum Emulator running on a Propeller :

Parallax Propeller :

[MacDeath]

Amstrad PC20..CGA ?

Ok, CGA was good in that it enabled to plug directly on a TV (the Sinclair's version).

Anyway this should have featured a "custom" EGA
Custom EGA... should had a 320x200x16/64 mode... or a way to re-assign the "CGA" inks from athe 64 palette...

This and the TV compatibility, despite this no enabling the HighRez modes...
So 2 Monitor plugs... TV-like and High Rez (EGA monitors ...)

Amstrad already had a lot of monitor available at the time (1986 ? 1987 ?)...
From the CPC's monitors (could run the lower resolution as it is basically a TV...) or the PC1640's EGA monitors.

After all, like AtariST...
You could get a 640x400x2 mode provided you got the right monitor, but on TVs got to stick to vertical 200 resolution...

and an AY soundchip IMO.
Those were also provided on Amstrad CPC and Speccies... they had the parts in stock...
And this could enable a sound compatibility with AtariST and Amstrad/Spectrum, hence the games developpers could make a good use of it.

So this should/could have been basically an ST/PC... the 16 bit amstrad could impose to the market and rape Atari's Market.


Oh, and a slightly betterly designed casing so you could put cards in it...

[arnoldemu]

Welcome to the cpcwiki forums!!!!