Jay West wrote on 4/2/2015 10:15 AM: Jay, I sold you an Intel MDS Series II probably about 15 years ago. If that's the one you are talking about, it is either a model 220 or 225 (the 220 is 8080-based and the 225 is 8085-based). Have you fired it up? Dave

Jay West wrote on 4/2/2015 6:18 PM: What is the symptom with the CRT? I think that was the achilles heel of the MDS. It usually was the connectors on the cable to the CRT control board. Some of the pins carry too much current and the heat made them go intermittent. The other problem that I found was on the control board inside of the CRT module. It was usually cold solder joints and a little touch up usually fixed it.

On Fri, Apr 3, 2015 at 2:30 AM, F.Ulivi <fulivi at tiscali.it> wrote: I'm 99% certain that the 8041 and 8041A masked ROMs can be read with essentially the same verification mode as the 8048 and 8048A, respectively. If I recall correctly, for the 8048, ROM verification mode works just like verification of the EPROM of an 8748, but with 12V on the PROG pin rather than 25V. The A-suffix parts have different programming/verification requirements than the non-A parts, so be careful.

On Wed, Apr 8, 2015 at 2:25 AM, F.Ulivi <fulivi at tiscali.it> wrote: Customers were always worried about it, but the IC vendors absolutely *had* to have a way to easily verify the full chip functionality, including verifying the ROM contents, so for a while that was more important than code security. As customers' interest in code security increased, first the vendors stopped documenting the verification mode of their chips (security through obscurity), and later implemented "real" security, for small values of "real". For all that I used a Series III MDS for *years*, I never actually took the cover off one back in the day, so I've seen the documentation on the IOC, but haven't previously seen the actual board. I have at hand an MDS-220 made in 1977, which I acquired some years back, and I no longer remember where this particular unit came from. It has the original 8080-based IPB CPU module, rather than the later 8085-based IPC. It does have an SBC 032 memory board to bring it up ot the full 64KB of RAM> Before today I had never powered up this particular MDS, but I did so a few hours ago. The first attempt did not produce a beep or any raster on the monitor, even with the brightness cranked to maximum. It turns out that two of the connectors to the IOC card were floating loose in the box, and one of the molex connectors was quite mangled. I can't really imagine how that happened, as the casing shows no obvious signs of abuse, only normal wear. I formed the connector pins back in to position as best I could by hand, and it now seems to work in diagnostic mode, which only tests the IOC. I haven't yet tried to use the ROM monitor of the IPB, and I don't presently have an ISIS-II boot floppy, or a CP/M boot floppy for the MDS, for that matter. There is some jitter in the vertical deflection, which seems to get worse as it warms up. Perhaps there is a capacitor going bad in the HV supply, though I'm no expert on CRT display repair. I've removed the IOC card and taken some photographs in preparation for dumping the EPROMs and the 8041A ROM. I'll have to knock together an apparatus to read the 8041A, but that shouldn't be difficult, other than that I can't use any of the modern microcontrollers I usually design with nowdays, because they aren't 5V tolerant. This IOC is the original model (not the IOC-III), but rather than the original fimrware it probably has the iMDX 511 IOC Firmware Enhancement Kit, because the keyboard does have the "FUNC" keycap which replaced the older "RPT" keycap. The IOC has four 2716 EPROMs of firmware, with part numbers 104692-001 through -004, a 2708 that I suspect is the character generator, part number 101539-001, and the 8041A, part number 104566-001. The photos of the IOC card are at: https://www.flickr.com/photos/22368471 at N04/sets/72157651893890975/