bfranchuk at jetnet.ab.ca bfranchuk at jetnet.ab.ca <mailto:cctalk%40classiccmp.org?Subject=Emailing%3A%20CP-M%20Z80%20home%20br ew%20computer%20circuit%20board.htm&In-Reply-To=CAD07A50FEA44B73BFD2864883FC 644B%40andrewdesktop> Sun Jun 15 20:05:45 CDT 2008 * Previous message: Emailing: CP-M Z80 home brew computer circuit board.htm * Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] ________________________________ Andrew Lynch wrote: to But when you think about it, most early CP/M machines were 8 inch single density. Not much on a disk and that I think is the basic format to look at. I think I seen a data separator using a 16 bit counter at 4x? the data rate but I can't remember where. I can't say I am having a nice day. I am still grumbling over not getting PAD's PCB and LAYOUT software when I could in the late 80's. I am looking to do a 16 bit (2901) cpu using EEPROM (2kx8 250 ns) and am still trying to find a schematic capture and PCB layout program that I can afford with through the whole parts. Sadly all seem to be Australia. :( Well, as my Mom likes to say "Talk is cheap. It takes money to buy whiskey." Data separators require either available chips or replacements with specific details. I designed an FDC data separator using plain 74LSxxx parts which is great in theory but there is no way I am going through the expense and time to build it when there are more pressing things to do. There is no guarantee it would work either. I am just an engineer, not a magician. If you look closely at those old 8" SSSD 8080 CP/M machines generally they use lots of SSI TTL and large PCBs. Were a similar computer designed today, it would cost a LOT of money to produce. They cost a lot then too. A home brew SBC using PCB of those sizes would be prohibitively expensive for most people. As for low cost EDA tools, have you tried KiCad and FreeRouting.net? There are links on the N8VEM website: http://groups.google.com/group/n8vem Originally, I designed the N8VEM SBC on notebook paper by hand. Later I recaptured the design with KiCad and used the FreeRouting.net autorouter/manual router. The N8VEM hardware documentation is done using KiCad/FreeRouting.net to create schematics, PCB layout, Gerber files, drill files, BOM, netlist, etc. KiCad is free (beer, speech) and FreeRouting.net is free (beer). They do a great job of schematic capture, PCB layout, have fairly complete parts library, have the ability to make custom parts, and do a great job of both autorouting and/or manual routing of PCB traces. Total cost $0. I doubt you'll find a 4 bit wide bit slice CPU (AMD2901) in the KiCad parts library. That part is a bit obscure these days. However, it'd probably be easy to do a custom part model since it is a plain 40 pin DIP with normal IO. The EEPROM is probably a 2816 or similar and is already in the extended parts library. Thanks and good luck with your project! Andrew Lynch