Re: Milwaukee Computers MC-1200
On Tue, Sep 4, 2018 at 10:00 AM, Al Kossow via cctalk wrote: > We have two in the CHM collection. This is the first time I've ever seen one > work. I was thinking it might be fun to try to get FORTH running on it. That sounds cool. > I may also mod mine so that it puts out proper RS-232 levels with a > piggyback board on the 1988. They just power it with +5v, which doesn't > work at all talking to my Mac. An old Wyse-75 wasn't so fussy. Hmm... I hadn't noticed that. Glad you pointed it out. I've had problems in the past with other machines and low-voltages on RS-232. > If you look at the schematic, they did some pretty weird things, like > using a 2758 for address decoding, and then there's the floppy disk > interface.. No error checking? I found that surprising - floppies are hardly reliable enough to forego error checking. > 1980 seems really late to be trying to build a system like this. Agreed. > It looks like a design OSI would have come up with. That was my thought when I saw the 6852. It was either because of OSI or they saw an app note somewhere and decided not to use a WD 177x chip. -ethan
Re: Milwaukee Computers MC-1200
On Tue, Sep 4, 2018 at 9:13 AM, John Foust via cctalk wrote: > At 09:58 AM 9/3/2018, Al Kossow via cctalk wrote: >>Ethan had asked me years ago to make copies of the software for this machine. >>It is pretty obscure, one full page add in Byte, and it sank without a trace. > Jon Auringer (of Madison, WI) mentioned having one of these on this list in > 2004. I got my unit directly from Jon when i was on a work trip to Madison but he didn't have any floppies for it then. Now, thanks to Al, I can burn some floppies and do more than interact with the ROMs. It's basically a generic 6502 with 64K of DRAM, 1-2 floppies (mine has 2) and as Al mentioned, an oddball sync-serial disk interface and boots up to an OS that favors p-System PASCAL apps. Definitely obscure. -ethan
Re: Milwaukee Computers MC-1200
On 9/4/18 6:13 AM, John Foust via cctalk wrote: Have you ever connected any names to this company - founders or employees? Nope. I had wondered if they were former GE Medical Systems people, being they were so close to their New Berlin plant. We have two in the CHM collection. This is the first time I've ever seen one work. I was thinking it might be fun to try to get FORTH running on it. I may also mod mine so that it puts out proper RS-232 levels with a piggyback board on the 1988. They just power it with +5v, which doesn't work at all talking to my Mac. An old Wyse-75 wasn't so fussy. If you look at the schematic, they did some pretty weird things, like using a 2758 for address decoding, and then there's the floppy disk interface.. No error checking? 1980 seems really late to be trying to build a system like this. It looks like a design OSI would have come up with.
Re: Milwaukee Computers MC-1200
At 09:58 AM 9/3/2018, Al Kossow via cctalk wrote: >Ethan had asked me years ago to make copies of the software for this machine. >It is pretty obscure, one full page add in Byte, and it sank without a trace. >6502, p-System, totally custom MFM-encoded floppy interface based on a Moto >6852 >synchronous serial interface chip. Interesting! Jon Auringer (of Madison, WI) mentioned having one of these on this list in 2004. Have you ever connected any names to this company - founders or employees? - John
Re: Milwaukee Computers MC-1200
On 09/03/2018 07:58 AM, Al Kossow via cctalk wrote: > One thing I noticed that made me nervous is looking at the code there is no > checksum on either the sector address or data fields on the floppy. I made an > image of a floppy that I bulk-erased and initialized this morning, and all you > see are the sync bytes and data, no trailing data where a crc would be. Looking at the ROM code disassembly, that certainly appears to be the case. Perhaps the attitude was "if you want to check your data, include a check in the data yourself". It wouldn't be the first time that this was done. Contrast with the Moto app note here for an 8" 3740-compatible setup using the 6852: http://www.bitsavers.org/components/motorola/6800/exorciser/AN764_A_Floppy_Disk_Controller_Using_the_MC6852_Oct76.pdf I recall that a friend had a KIM-1 with the KMISI expansion and a single SA400 floppy disk drive. I don't recall the details, but getting reliable operation was nearly impossible. --Chuck
Milwaukee Computers MC-1200
Another small project off my plate. Ethan had asked me years ago to make copies of the software for this machine. It is pretty obscure, one full page add in Byte, and it sank without a trace. 6502, p-System, totally custom MFM-encoded floppy interface based on a Moto 6852 synchronous serial interface chip. I had bought a Supercard Pro a while ago, and set it up to do some hard-sectored floppy imaging. Figured this would be a good test case, since it didn't have the problems with dealing with out of sync data streams (the SCP doesn't grok more than one sector hole so you have to turn off index synchronization). Made images, dragged my machine out of storage, cleaned it up, made a clone from the SCP image, and it booted! yay! SCP images are up under http://bitsavers.org/bits/MilwaukeeComputers I also put up cleaner images of the schematic and board layout, and annotated a disassembly of the boot prom from a scanned listing i've had for a while under http://bitsavers.org/pdf/milwaukeeComputers One thing I noticed that made me nervous is looking at the code there is no checksum on either the sector address or data fields on the floppy. I made an image of a floppy that I bulk-erased and initialized this morning, and all you see are the sync bytes and data, no trailing data where a crc would be.
