Hi John, My current inventory of MCS-80 components: C8080A CPU (gold/white) P8212 8-bit I/O port C8214 priority interrupt control (gold/white) (2) D8216 4-bit bi-directional bus driver D8228 system controller & bus driver (2) D8238 system controller & bus driver C8255 programmable peripheral interface (gold/white) (3) C2112A 256x1 bit SRAM (gold/white) I'm sure I'm probably missing one or two crucial support chips. I'll definitely need a bunch of a much higher capacity RAM, since 96 bytes just doesn't seem like enough. I'm pretty sure I have a ton of SRAM chips of more reasonable capacity but I just have to dig them out. Same goes for EPROMS As as far as construction and form factor, I was thinking about doing it on s100 prototype boards and a large backplane so that I could add commercially built cards to the system. I might eventually want to add a floppy controller. I know it would probably make more sense to use some type of flash interface, but I want this machine to be configured as if it was built in the late seventies or early eighties. Thanks, Joe Giliberti On Sat, Jan 1, 2022, 7:11 PM Jonathan Chapman via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:

Welcome back! If you aren't doing a S-100 compatible setup, do use the Intel 8228 system controller. It makes life *much* nicer.

If you're using MCS-80 parts anyway, the Intel 8251 or 8251A is a solid choice for your serial chip.

You will need either a power-on jump circuit (see Cromemco ZPU) or ROM relocation circuit (you're welcome to use the one from the 8085 SBC rev 3 if you like) to keep ROM from being hardwired at 0x0000, which is incompatible with CP/M.

Probably best to use modern SRAM, or at least modernish byte-wide stuff like the 62256, 6264, or 6116, just to avoid having to get a ton of old power-hungry RAM.

There are lots of ROM monitors available, I of course usually customize GWMON-80 for systems I'm bringing up:

https://github.com/glitchwrks/gwmon-80

Just restructured and cleaned up the source a month or so ago and decided to call it V1!

Thanks, Jonathan

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Saturday, January 1st, 2022 at 14:48, Joseph Giliberti via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:

...

Greetings Everyone,

I'm Joe Giliberti. I had been a member of the original MARCH up until 10 or

so years ago, when a personal issue prompted me to leave. It also didn't

help matters that it took me more time than most to grow up into a

responsible adult. Now that many things have changed and that I've been

getting back into the hobby over the past few years, I've decided to come

back. I keep making plans to get to events but something always seems to

interfere. I'm really hoping I'll be able to get to the workshop on Sunday.

Any who, in the past few years I've been getting more and more into the

hobby, doing lots of reading to expand my knowledge beyond writing BASIC on

my Apple IIe. I've decided that I want to take a shot at constructing a

basic computer.

Over the years, I've been amassing component parts from estate sales and

one particularly lucky estate cleanout. Among other things, I've

accumulated thousands of capacitors, resistors, transistors and diodes,

hundreds of 7400 series TTL and quite a few microprocessors and support

chips.

I think I want to base the computer around an 8080. There are the two main

reasons I want to go this route:

-I have an 8080A and many of the support chips, most of which are of the

early gold and white ceramic design.

-Ultimately, I want the system to be capable of running CP/M

Initially, I'm not looking to make it overly complicated. Ideally, I'd like

to have a machine language monitor and TinyBASIC in ROM. I'd also like a

serial connection for I/O and a cassette interface for mass storage. If

someday I get really ambitious, I might look into things like video

hardware and floppy disk mass storage, but I need to take care of the

basics first

I still need to do a lot more research and study before I start doing

things like design and construction, but I would very much appreciate any

suggestions or feedback on my plans for this endeavor.

Thanks and Happy New Year!

Joe Giliberti

John, Thank you for your expertise on the matter. I'm very much still learning and appreciate any and all input. Getting to the point of layout and assembly is probably months away, so I've got time. Thanks again. Joe Giliberti On Sat, Jan 1, 2022, 8:42 PM Jonathan Chapman <lists@glitchwrks.com> wrote:

My current inventory of MCS-80 components: C8080A CPU (gold/white) P8212 8-bit I/O port C8214 priority interrupt control (gold/white) (2) D8216 4-bit bi-directional bus driver D8228 system controller & bus driver (2) D8238 system controller & bus driver C8255 programmable peripheral interface (gold/white) (3) C2112A 256x1 bit SRAM (gold/white)

Looks like you about have the contents of the SDK-80 starter kit!

I'm sure I'm probably missing one or two crucial support chips.

Just the 8224 clock generator, which is pretty important -- it's a hassle to do it without. Let me know if you need one, I have several NOS parts and around 300x Soviet clones (which run cooler anyway).

I'll definitely need a bunch of a much higher capacity RAM, since 96 bytes just doesn't seem like enough. I'm pretty sure I have a ton of SRAM chips of more reasonable capacity but I just have to dig them out. Same goes for EPROMS

Realistically it makes the most sense to go with a 2716 EPROM or newer, as there are usually drop-in EEPROM options, and you can program with even modern-ish programmers. Plus they're typically 5V only after that point, except for some sort of oddball TI parts.

As as far as construction and form factor, I was thinking about doing it on s100 prototype boards and a large backplane so that I could add commercially built cards to the system.

You probably want to actually do S-100 then, there are better backplane/connector options if you're not actually going to implement S-100 bus. Plus, as you say, that opens you up to a ton of ready made cards!

I might eventually want to add a floppy controller. I know it would probably make more sense to use some type of flash interface, but I want this machine to be configured as if it was built in the late seventies or early eighties.

Nothing wrong with floppies! That's mostly what I use.

Thanks, Jonathan