I am working on a Z80 SBC home brew project and am looking for some
experienced persons who are interested in early testing and
development. Preferrably with electronic technician and/or engineer
with home brew SBC experience with your own tools and workbench.
The project is a Z80 SBC currently in transition from a prototype
board based system to a manufactured PCB. The previous version using
the prototype board worked OK on my bench so I am fairly confident in
the basic design. My plan is to move to a manufactured PCB to make
assembly and test much easier so I have redesigned the SBC.
Designed as a "new vintage" SBC it is made in the classic style: using
commonly available 100% through-hole DIP TTL chips (mostly 74LSxxx SSI
and MSI with a few common LSI), no programmable parts (PALs, GALs,
CPLDs, or FPGAs, etc) except for the EPROM. The intent is to make the
SBC easily assembled and tested with only basic tools (soldering iron
and VOM only -- Logic probe and oscilloscope are handy too).
The prototype board version has a monitor and CBIOS for booting CP/M
and supports a 32Kx8 EEPROM and 512Kx8 SRAM drive. The PCB version
has been modified to support a 1MBx8 EPROM drive instead of the 32Kx8
EEPROM. It includes basic 16550 UART, 8250 PPI, DS1302 RTC, and ECB
bus interface IO. The design attempts to keep the cost low but due to
several factors will probably cost around is estimated to be around
$100 for the parts.
If you are interested, please contact me offline. Thanks!
"lynchaj" <lynchaj@yahoo.com> wrote in message
news:dc3c867b-8946-4482-8e7f-42cb7beb9196@m44g2000hsc.googlegroups.com...
> Hi,
>
> I am working on a Z80 SBC home brew project and am looking for some
> experienced persons who are interested in early testing and
> development. Preferrably with electronic technician and/or engineer
> with home brew SBC experience with your own tools and workbench.
>
> The project is a Z80 SBC currently in transition from a prototype
> board based system to a manufactured PCB. The previous version using
> the prototype board worked OK on my bench so I am fairly confident in
> the basic design. My plan is to move to a manufactured PCB to make
> assembly and test much easier so I have redesigned the SBC.
>
> Designed as a "new vintage" SBC it is made in the classic style: using
> commonly available 100% through-hole DIP TTL chips (mostly 74LSxxx SSI
> and MSI with a few common LSI), no programmable parts (PALs, GALs,
> CPLDs, or FPGAs, etc) except for the EPROM. The intent is to make the
> SBC easily assembled and tested with only basic tools (soldering iron
> and VOM only -- Logic probe and oscilloscope are handy too).
>
> The prototype board version has a monitor and CBIOS for booting CP/M
> and supports a 32Kx8 EEPROM and 512Kx8 SRAM drive. The PCB version
> has been modified to support a 1MBx8 EPROM drive instead of the 32Kx8
> EEPROM. It includes basic 16550 UART, 8250 PPI, DS1302 RTC, and ECB
> bus interface IO. The design attempts to keep the cost low but due to
> several factors will probably cost around is estimated to be around
> $100 for the parts.
>
> If you are interested, please contact me offline. Thanks!
>
> Andrew Lynch
Interesting but I think they are already out there in the $30 price range
On Apr 26, 2:05*pm, "philo" <ph...@privacy.net> wrote:
> "lynchaj" <lync...@yahoo.com> wrote in message
>
> news:dc3c867b-8946-4482-8e7f-42cb7beb9196@m44g2000hsc.googlegroups.com...
>
>
>
>
>
> > Hi,
>
> > I am working on a Z80 SBC home brew project and am looking for some
> > experienced persons who are interested in early testing and
> > development. *Preferrably with electronic technician and/or engineer
> > with home brew SBC experience with your own tools and workbench.
>
> > The project is a Z80 SBC currently in transition from a prototype
> > board based system to a manufactured PCB. *The previous version using
> > the prototype board worked OK on my bench so I am fairly confident in
> > the basic design. *My plan is to move to a manufactured PCB to make
> > assembly and test much easier so I have redesigned the SBC.
>
> > Designed as a "new vintage" SBC it is made in the classic style: using
> > commonly available 100% through-hole DIP TTL chips (mostly 74LSxxx SSI
> > and MSI with a few common LSI), no programmable parts (PALs, GALs,
> > CPLDs, or FPGAs, etc) except for the EPROM. *The intent is to make the
> > SBC easily assembled and tested with only basic tools (soldering iron
> > and VOM only -- Logic probe and oscilloscope are handy too).
>
> > The prototype board version has a monitor and CBIOS for booting CP/M
> > and supports a 32Kx8 EEPROM and 512Kx8 SRAM drive. *The PCB version
> > has been modified to support a 1MBx8 EPROM drive instead of the 32Kx8
> > EEPROM. *It includes basic 16550 UART, 8250 PPI, DS1302 RTC, and ECB
> > bus interface IO. *The design attempts to keep the cost low but due to
> > several factors will probably cost around is estimated to be around
> > $100 for the parts.
>
> > If you are interested, please contact me offline. *Thanks!
>
> > Andrew Lynch
>
> Interesting but I think they are already out there in the $30 price range- Hide quoted text -
>
> - Show quoted text -
Hi,
A home brew Z80 with a manufactured PCB for $30? I surely would like
to see that. Got any URLs?
There are lots of Z80 projects out there with schematics but very few
with PCBs especially available ones.
The P112 when it was available was $165 US. I think you'll be hard
pressed to show any examples.
"lynchaj" <lynchaj@yahoo.com> wrote in message
news:ff4be93c-e961-423c-8a35-f8f68564fa8a@r66g2000hsg.googlegroups.com...
On Apr 26, 2:05 pm, "philo" <ph...@privacy.net> wrote:
> "lynchaj" <lync...@yahoo.com> wrote in message
>
> news:dc3c867b-8946-4482-8e7f-42cb7beb9196@m44g2000hsc.googlegroups.com...
>
>
>
>
>
> > Hi,
>
> > I am working on a Z80 SBC home brew project and am looking for some
> > experienced persons who are interested in early testing and
> > development. Preferrably with electronic technician and/or engineer
> > with home brew SBC experience with your own tools and workbench.
>
> > The project is a Z80 SBC currently in transition from a prototype
> > board based system to a manufactured PCB. The previous version using
> > the prototype board worked OK on my bench so I am fairly confident in
> > the basic design. My plan is to move to a manufactured PCB to make
> > assembly and test much easier so I have redesigned the SBC.
>
> > Designed as a "new vintage" SBC it is made in the classic style: using
> > commonly available 100% through-hole DIP TTL chips (mostly 74LSxxx SSI
> > and MSI with a few common LSI), no programmable parts (PALs, GALs,
> > CPLDs, or FPGAs, etc) except for the EPROM. The intent is to make the
> > SBC easily assembled and tested with only basic tools (soldering iron
> > and VOM only -- Logic probe and oscilloscope are handy too).
>
> > The prototype board version has a monitor and CBIOS for booting CP/M
> > and supports a 32Kx8 EEPROM and 512Kx8 SRAM drive. The PCB version
> > has been modified to support a 1MBx8 EPROM drive instead of the 32Kx8
> > EEPROM. It includes basic 16550 UART, 8250 PPI, DS1302 RTC, and ECB
> > bus interface IO. The design attempts to keep the cost low but due to
> > several factors will probably cost around is estimated to be around
> > $100 for the parts.
>
> > If you are interested, please contact me offline. Thanks!
>
> > Andrew Lynch
>
> Interesting but I think they are already out there in the $30 price range-
> Hide quoted text -
>
> - Show quoted text -
Hi,
A home brew Z80 with a manufactured PCB for $30? I surely would like
to see that. Got any URLs?
There are lots of Z80 projects out there with schematics but very few
with PCBs especially available ones.
The P112 when it was available was $165 US. I think you'll be hard
pressed to show any examples.
On Apr 26, 4:13*pm, "philo" <ph...@privacy.net> wrote:
> "lynchaj" <lync...@yahoo.com> wrote in message
>
> news:ff4be93c-e961-423c-8a35-f8f68564fa8a@r66g2000hsg.googlegroups.com...
> On Apr 26, 2:05 pm, "philo" <ph...@privacy.net> wrote:
>
>
>
>
>
> > "lynchaj" <lync...@yahoo.com> wrote in message
>
> >news:dc3c867b-8946-4482-8e7f-42cb7beb9196@m44g2000hsc.googlegroups.com...
>
> > > Hi,
>
> > > I am working on a Z80 SBC home brew project and am looking for some
> > > experienced persons who are interested in early testing and
> > > development. Preferrably with electronic technician and/or engineer
> > > with home brew SBC experience with your own tools and workbench.
>
> > > The project is a Z80 SBC currently in transition from a prototype
> > > board based system to a manufactured PCB. The previous version using
> > > the prototype board worked OK on my bench so I am fairly confident in
> > > the basic design. My plan is to move to a manufactured PCB to make
> > > assembly and test much easier so I have redesigned the SBC.
>
> > > Designed as a "new vintage" SBC it is made in the classic style: using
> > > commonly available 100% through-hole DIP TTL chips (mostly 74LSxxx SSI
> > > and MSI with a few common LSI), no programmable parts (PALs, GALs,
> > > CPLDs, or FPGAs, etc) except for the EPROM. The intent is to make the
> > > SBC easily assembled and tested with only basic tools (soldering iron
> > > and VOM only -- Logic probe and oscilloscope are handy too).
>
> > > The prototype board version has a monitor and CBIOS for booting CP/M
> > > and supports a 32Kx8 EEPROM and 512Kx8 SRAM drive. The PCB version
> > > has been modified to support a 1MBx8 EPROM drive instead of the 32Kx8
> > > EEPROM. It includes basic 16550 UART, 8250 PPI, DS1302 RTC, and ECB
> > > bus interface IO. The design attempts to keep the cost low but due to
> > > several factors will probably cost around is estimated to be around
> > > $100 for the parts.
>
> > > If you are interested, please contact me offline. Thanks!
>
> > > Andrew Lynch
>
> > Interesting but I think they are already out there in the $30 price range-
> > Hide quoted text -
>
> > - Show quoted text -
>
> Hi,
>
> A home brew Z80 with a manufactured PCB for $30? *I surely would like
> to see that. *Got any URLs?
>
> There are lots of Z80 projects out there with schematics but very few
> with PCBs especially available ones.
>
> The P112 when it was available was $165 US. *I think you'll be hard
> pressed to show any examples.
>
> Thanks!
>
> Andrew Lynch
>
> I found this
>
> http://home.att.net/~wzmicro/prod02.htm- Hide quoted text -
>
> - Show quoted text -
Well, OK, that is a $30 Z80 SBC but not a home brew computer. I think
you are missing the point.
"lynchaj" <lynchaj@yahoo.com> wrote in message
news:a74ac1e7-f3eb-4d3e-893a-8c2db599f4d5@w74g2000hsh.googlegroups.com...
On Apr 26, 4:13 pm, "philo" <ph...@privacy.net> wrote:
> "lynchaj" <lync...@yahoo.com> wrote in message
>
> news:ff4be93c-e961-423c-8a35-f8f68564fa8a@r66g2000hsg.googlegroups.com...
> On Apr 26, 2:05 pm, "philo" <ph...@privacy.net> wrote:
>
>
>
>
>
> > "lynchaj" <lync...@yahoo.com> wrote in message
>
> >news:dc3c867b-8946-4482-8e7f-42cb7beb9196@m44g2000hsc.googlegroups.com...
>
> > > Hi,
>
> > > I am working on a Z80 SBC home brew project and am looking for some
> > > experienced persons who are interested in early testing and
> > > development. Preferrably with electronic technician and/or engineer
> > > with home brew SBC experience with your own tools and workbench.
>
> > > The project is a Z80 SBC currently in transition from a prototype
> > > board based system to a manufactured PCB. The previous version using
> > > the prototype board worked OK on my bench so I am fairly confident in
> > > the basic design. My plan is to move to a manufactured PCB to make
> > > assembly and test much easier so I have redesigned the SBC.
>
> > > Designed as a "new vintage" SBC it is made in the classic style: using
> > > commonly available 100% through-hole DIP TTL chips (mostly 74LSxxx SSI
> > > and MSI with a few common LSI), no programmable parts (PALs, GALs,
> > > CPLDs, or FPGAs, etc) except for the EPROM. The intent is to make the
> > > SBC easily assembled and tested with only basic tools (soldering iron
> > > and VOM only -- Logic probe and oscilloscope are handy too).
>
> > > The prototype board version has a monitor and CBIOS for booting CP/M
> > > and supports a 32Kx8 EEPROM and 512Kx8 SRAM drive. The PCB version
> > > has been modified to support a 1MBx8 EPROM drive instead of the 32Kx8
> > > EEPROM. It includes basic 16550 UART, 8250 PPI, DS1302 RTC, and ECB
> > > bus interface IO. The design attempts to keep the cost low but due to
> > > several factors will probably cost around is estimated to be around
> > > $100 for the parts.
>
> > > If you are interested, please contact me offline. Thanks!
>
> > > Andrew Lynch
>
> > Interesting but I think they are already out there in the $30 price
> > range-
> > Hide quoted text -
>
> > - Show quoted text -
>
> Hi,
>
> A home brew Z80 with a manufactured PCB for $30? I surely would like
> to see that. Got any URLs?
>
> There are lots of Z80 projects out there with schematics but very few
> with PCBs especially available ones.
>
> The P112 when it was available was $165 US. I think you'll be hard
> pressed to show any examples.
>
> Thanks!
>
> Andrew Lynch
>
> I found this
>
> http://home.att.net/~wzmicro/prod02.htm- Hide quoted text -
>
> - Show quoted text -
Well, OK, that is a $30 Z80 SBC but not a home brew computer. I think
you are missing the point.
Have a nice day.
Andrew Lynch
I guess I did not realize you are building an entire computer.
Well, if I want to run CP/M all I have to do it go up into my attic and
bring down my Kaypro !!! <G>
BTW: The company I work for has some controls that were built back around
1982 that use the Z80.
The equipment is still in production... those things are still alive today !
It's not critical...but funny. When the "off" button is pushed, there is
about a 4 second delay to shut down.
Our newer controls with faster cpu's don't do that !
On Apr 26, 7:19*pm, "philo" <ph...@privacy.net> wrote:
> "lynchaj" <lync...@yahoo.com> wrote in message
>
> news:a74ac1e7-f3eb-4d3e-893a-8c2db599f4d5@w74g2000hsh.googlegroups.com...
> On Apr 26, 4:13 pm, "philo" <ph...@privacy.net> wrote:
>
>
>
>
>
> > "lynchaj" <lync...@yahoo.com> wrote in message
>
> >news:ff4be93c-e961-423c-8a35-f8f68564fa8a@r66g2000hsg.googlegroups.com...
> > On Apr 26, 2:05 pm, "philo" <ph...@privacy.net> wrote:
>
> > > "lynchaj" <lync...@yahoo.com> wrote in message
>
> > >news:dc3c867b-8946-4482-8e7f-42cb7beb9196@m44g2000hsc.googlegroups.com....
>
> > > > Hi,
>
> > > > I am working on a Z80 SBC home brew project and am looking for some
> > > > experienced persons who are interested in early testing and
> > > > development. Preferrably with electronic technician and/or engineer
> > > > with home brew SBC experience with your own tools and workbench.
>
> > > > The project is a Z80 SBC currently in transition from a prototype
> > > > board based system to a manufactured PCB. The previous version using
> > > > the prototype board worked OK on my bench so I am fairly confident in
> > > > the basic design. My plan is to move to a manufactured PCB to make
> > > > assembly and test much easier so I have redesigned the SBC.
>
> > > > Designed as a "new vintage" SBC it is made in the classic style: using
> > > > commonly available 100% through-hole DIP TTL chips (mostly 74LSxxx SSI
> > > > and MSI with a few common LSI), no programmable parts (PALs, GALs,
> > > > CPLDs, or FPGAs, etc) except for the EPROM. The intent is to make the
> > > > SBC easily assembled and tested with only basic tools (soldering iron
> > > > and VOM only -- Logic probe and oscilloscope are handy too).
>
> > > > The prototype board version has a monitor and CBIOS for booting CP/M
> > > > and supports a 32Kx8 EEPROM and 512Kx8 SRAM drive. The PCB version
> > > > has been modified to support a 1MBx8 EPROM drive instead of the 32Kx8
> > > > EEPROM. It includes basic 16550 UART, 8250 PPI, DS1302 RTC, and ECB
> > > > bus interface IO. The design attempts to keep the cost low but due to
> > > > several factors will probably cost around is estimated to be around
> > > > $100 for the parts.
>
> > > > If you are interested, please contact me offline. Thanks!
>
> > > > Andrew Lynch
>
> > > Interesting but I think they are already out there in the $30 price
> > > range-
> > > Hide quoted text -
>
> > > - Show quoted text -
>
> > Hi,
>
> > A home brew Z80 with a manufactured PCB for $30? I surely would like
> > to see that. Got any URLs?
>
> > There are lots of Z80 projects out there with schematics but very few
> > with PCBs especially available ones.
>
> > The P112 when it was available was $165 US. I think you'll be hard
> > pressed to show any examples.
>
> > Thanks!
>
> > Andrew Lynch
>
> > I found this
>
> >http://home.att.net/~wzmicro/prod02.htm-Hide quoted text -
>
> > - Show quoted text -
>
> Well, OK, that is a $30 Z80 SBC but not a home brew computer. *I think
> you are missing the point.
>
> Have a nice day.
>
> Andrew Lynch
>
> I guess I did not realize you are building an entire computer.
> Well, if I want to run CP/M all I have to do it go up into my attic and
> bring down my Kaypro !!! * <G>
>
> BTW: The company I work for has some controls that were built back around
> 1982 that use the Z80.
> The equipment is still in production... those things are still alive today !
>
> It's not critical...but funny. When the "off" button is pushed, there is
> about a 4 second delay to shut down.
> Our newer controls with faster cpu's don't do that !- Hide quoted text -
>
> - Show quoted text -
Hi,
True, if all I wanted to do was run CP/M, I could run it on any number
of Z80 computers including a Kaypro. There are working CP/M computers
available on Ebay for $50 or often less. However, running CP/M is not
the point. This project is about building true home brew computers
which is *almost* a lost art these days.
I believe most people have not considered building their own computers
from scratch. There was a day not long ago when people would
regularly build their own computers at the component level (ie using
ICs and passive devices with soldered connections or using wire
wrap). Some even designed their own CPUs using just transistors and
passive components.
While it is probably not realistic to build recent 32 or 64 bit
computers from scratch, the older 8 bit (Z80, 6502, 6809) and even
some 16 bit systems can still be practically done on a hobbyist
workbench using commonly available parts and tools.
That is what this project is about. It started as an empty prototype
board and some ideas. I would like to make it more available to other
people who are also interested in truly building their own home brew
computer from scratch.
I am not claiming this is unprecedented or some novel idea. There
have been numerous home brew computer projects in the past. P112 is a
great example as are many others. However, most projects assume a
high skill level and/or access to specialized equipment/parts. For
example, P112 includes schematics and PCB designs but relies on
difficult to obtain parts and also uses SMT components, neither of
which are readily available to many hobbyist builders.
Projects which only provide schematics leave it to the builder how to
actually create the board which I have found to be a critical design
consideration. Using breadboards, wire wrap techniques, and prototype
boards all have their strengths and weaknesses but none match the
benefits of a real manufactured PCB.
<snip>
>
> I guess I did not realize you are building an entire computer.
> Well, if I want to run CP/M all I have to do it go up into my attic and
> bring down my Kaypro !!! <G>
>
> BTW: The company I work for has some controls that were built back around
> 1982 that use the Z80.
> The equipment is still in production... those things are still alive today
!
>
> It's not critical...but funny. When the "off" button is pushed, there is
> about a 4 second delay to shut down.
> Our newer controls with faster cpu's don't do that !- Hide quoted text -
>
> - Show quoted text -
Hi,
True, if all I wanted to do was run CP/M, I could run it on any number
of Z80 computers including a Kaypro. There are working CP/M computers
available on Ebay for $50 or often less. However, running CP/M is not
the point. This project is about building true home brew computers
which is *almost* a lost art these days.
I believe most people have not considered building their own computers
from scratch. There was a day not long ago when people would
regularly build their own computers at the component level (ie using
ICs and passive devices with soldered connections or using wire
wrap). Some even designed their own CPUs using just transistors and
passive components.
While it is probably not realistic to build recent 32 or 64 bit
computers from scratch, the older 8 bit (Z80, 6502, 6809) and even
some 16 bit systems can still be practically done on a hobbyist
workbench using commonly available parts and tools.
That is what this project is about. It started as an empty prototype
board and some ideas. I would like to make it more available to other
people who are also interested in truly building their own home brew
computer from scratch.
I am not claiming this is unprecedented or some novel idea. There
have been numerous home brew computer projects in the past. P112 is a
great example as are many others. However, most projects assume a
high skill level and/or access to specialized equipment/parts. For
example, P112 includes schematics and PCB designs but relies on
difficult to obtain parts and also uses SMT components, neither of
which are readily available to many hobbyist builders.
Projects which only provide schematics leave it to the builder how to
actually create the board which I have found to be a critical design
consideration. Using breadboards, wire wrap techniques, and prototype
boards all have their strengths and weaknesses but none match the
benefits of a real manufactured PCB.
Thanks!
Andrew Lynch
Well it sounds like a good project to me.
Somewhere around 1980 or so I built a micro-computer as an independent study
course
when I was going to night school. It was based on the 68000 and was to serve
as an EPROM programmer.
At the time, I was taking a programming class and could not believe that we
still had to use punch cards.
I hated that so much that I stayed far away from computers for many years!
BTW: When I was a kid, I was an active ham radio operator and it seemed like
practically
everyone had a homebrew project...where we built out equipment from scratch.
I used to feel like I had really accomplished something until our advisor
just laughed
and told us that when he was a kid...they even built their own components.
Though of course we all wound our own coils...
we sat in amazement when he told us that a capacitor was made by filling a
zinc tub with salt water...
then putting beer bottles (also filled with salt water) into the tub and
wiring them together by inserting
wires into the bottles.
A grid leak resistor was made by a heavy pencil lead line on a piece of
paper!
Times have changed...to I salute you for your fine endeavor!!!
> I believe most people have not considered building their own computers
> from scratch. There was a day not long ago when people would
> regularly build their own computers at the component level (ie using
> ICs and passive devices with soldered connections or using wire
> wrap). Some even designed their own CPUs using just transistors and
> passive components.
The impression I get is that far more people are doing this kind
of thing than ever before in absolute terms. The only difference
is that it's a much smaller percentage of computer users in general.
In addition, they tend not to be using loose microprocessors like
the Z80, the preference today is for integrated microcontrollers
that provide the processor, RAM, ROM and a few peripherals on a
chip whereas a Z80 will probably be four or five chips and a whole
lot of wiring (PCB or otherwise) just for the processor and some
RAM and ROM.
> While it is probably not realistic to build recent 32 or 64 bit
> computers from scratch, the older 8 bit (Z80, 6502, 6809) and even
> some 16 bit systems can still be practically done on a hobbyist
> workbench using commonly available parts and tools.
People are still doing it, but they're not soldering together loose
74 series logic chips anymore. The most common method now is by
simply programming an FPGA with your design. Much faster and more
reliable than a breadboard with hundreds of loose wires hanging
out of it.
> That is what this project is about. It started as an empty prototype
> board and some ideas. I would like to make it more available to other
> people who are also interested in truly building their own home brew
> computer from scratch.
It needn't be that difficult. Presumably you'll want at least a
clock, some ROM and some RAM. For simplicity I'd suggest going
for 16K ROM, 16K RAM, and two sockets that can be filled with either
depending on the needs of the application. Peripherals are the
big unknown. You could interface a 16 key keypad and a couple of
seven segment LED displays for a simple self contained unit, but
for less money and greater capability I'd be tempted to add an
RS232 port and hook it up to a dumb terminal (or more likely PC
running Hyperterminal or similar) and use that as your display.
16K ROM should be plenty of space for a simple ROM monitor and
XMODEM client to download programs from the PC, with space left
for a few gneral purpose library functions. You should be able to
get the appropriate portions of the ANSI C library and a conio
equivalent in there for instance. Running CP/M may be a little
more challenging since in pratice it always needed tweaking for
the specific hardware it was running on.
On Apr 27, 3:32*pm, Andrew Smallshaw <andr...@sdf.lonestar.org> wrote:
> On 2008-04-27, lynchaj <lync...@yahoo.com> wrote:
>
> <huge snip that should have been done long ago>
>
> > I believe most people have not considered building their own computers
> > from scratch. *There was a day not long ago when people would
> > regularly build their own computers at the component level (ie using
> > ICs and passive devices with soldered connections or using wire
> > wrap). *Some even designed their own CPUs using just transistors and
> > passive components.
>
> The impression I get is that far more people are doing this kind
> of thing than ever before in absolute terms. *The only difference
> is that it's a much smaller percentage of computer users in general.
>
> In addition, they tend not to be using loose microprocessors like
> the Z80, the preference today is for integrated microcontrollers
> that provide the processor, RAM, ROM and a few peripherals on a
> chip whereas a Z80 will probably be four or five chips and a whole
> lot of wiring (PCB or otherwise) just for the processor and some
> RAM and ROM.
>
Hi Andrew,
You could be right, I have no way of knowing for sure. My guess based
on discussions with people familiar with computers is that few do
anything with hardware except a few brave ones may build their own
systems or add a peripheral occasionally. Actually get out the
soldering iron and VOM and building something is pretty rare, I think.
Agree -- the options for integrated CPU chips like MC68HC11 and the
Zilog Z8 family are making a PCB full of chips an obsolete form of
electronics. Especially the PIC and AVR families of
microcontrollers. No argument there. Making a small computer with
the Z80 will be 5 or so large chips and about 10 to 20 small chips
depending on what IO you add. The smallest Z80 SBC made from common
parts (ie not programmable parts will be around 12 or so chips total)
but will be very limited in capability.
> > While it is probably not realistic to build recent 32 or 64 bit
> > computers from scratch, the older 8 bit (Z80, 6502, 6809) and even
> > some 16 bit systems can still be practically done on a hobbyist
> > workbench using commonly available parts and tools.
>
> People are still doing it, but they're not soldering together loose
> 74 series logic chips anymore. *The most common method now is by
> simply programming an FPGA with your design. *Much faster and more
> reliable than a breadboard with hundreds of loose wires hanging
> out of it.
>
True, what people have done with FPGA and CPLDs is amazing. Although
I think rather defeats the whole vintage electronics feel though and
starts to resemble computer pure programming. I can see the appeal
though, the PCB layouts are amazingly simple and the boards are tiny
and nearly empty. Basically just a big Xilinx FPGA in the center and
some connectors. Maybe some passive components but few of those.
> > That is what this project is about. *It started as an empty prototype
> > board and some ideas. *I would like to make it more available to other
> > people who are also interested in truly building their own home brew
> > computer from scratch.
>
> It needn't be that difficult. *Presumably you'll want at least a
> clock, some ROM and some RAM. *For simplicity I'd suggest going
> for 16K ROM, 16K RAM, and two sockets that can be filled with either
> depending on the needs of the application. *Peripherals are the
> big unknown. *You could interface a 16 key keypad and a couple of
> seven segment LED displays for a simple self contained unit, but
> for less money and greater capability I'd be tempted to add an
> RS232 port and hook it up to a dumb terminal (or more likely PC
> running Hyperterminal or similar) and use that as your display.
>
It is not supposed to be difficult, it is supposed to be fun and a
hobby. The problem comes in during expansion and continued
integration and test. Getting the basic computer working with a UART
for IO is pretty straight forward. However, expanding it to include
more rich forms of IO gets increasingly difficult without some form of
modularity. Also fixing problems when they creep into a point to
point wired board or wire wrap can be frustrating as they are a lot
less robust than a manufactured PCB in my opinion.
I would just like to "lower the bar" a bit so others can join in the
fun too. Make a PCB available which uses common tools and parts would
do that, I think. It might not but who knows? The P112 surely has
lots of fans and it used about 4 SMT components and some highly
integrated IO chips. It "sort of" has a bus connector but I don't
recall seeing any peripherals for it. I could be wrong though.
Maybe building 74LSxxx TTL chip homebrew computers has finally passed
into obscurity. Oh well, at least I still enjoy it. I will continue
the hobby simply because it is so enjoyable to make things work. Of
course, I enjoy repairing and working with the vintage microcomputers
of the CP/M era (Heath, NorthStar, Vector Graphic, etc) so that
effects my view point.
> 16K ROM should be plenty of space for a simple ROM monitor and
> XMODEM client to download programs from the PC, with space left
> for a few gneral purpose library functions. *You should be able to
> get the appropriate portions of the ANSI C library and a conio
> equivalent in there for instance. *Running CP/M may be a little
> more challenging since in pratice it always needed tweaking for
> the specific hardware it was running on.
>
> --
> Andrew Smallshaw
> andr...@sdf.lonestar.org
Yes, I did that with my test prototype system. I was able to get it
to boot CP/M from a ROM drive and use the RAM drive for storage.
Worked great and even added an IDE interface. That was surprisingly
easy -- even the CBIOS was not that difficult. I got as far as
building a floppy disk interface before the inevitable creep of poor
grounding and power distribution problems finally caught up with me.
At that point it was such a complicated bundle of wires that it was
not so much fun.
I have the desire to keep developing with the system but before I do,
I am making PCBs to help "clean up" the design. This time I am paying
lot more attention to power and grounding issues. We'll see how it
works out this time.
Z80 home brew project 
Linear Mode
