*** M E M O R U M ***

ROM Update to build 117 There's now an option to run a monitor type facility to display and write the ram. As with the rest of the rom, the dump, edit and fill routines don't use any ram themselves. Menu117.JPG The monitor scrolls up from the bottom leaving reminder of the options on the top lines. ...

It looks line Mame might be initialising the video ram to zero. The real MTX can have junk in there on boot, so my emulator doesn't bother to clear it. The test rom didn't either, so I'm getting junk on the display for codes less than 32. On the latest build the first 32 character codes are defined ...

Final posting for the day The menu has gained an extra function, seen here from a screen dump in the emulator while testing. Menu.JPG The ram test is now clever enough to spot a duff multiplexer ! RamTesting.JPG And last but not least, the output from the rom test EasterEgg.JPG The question is now, ...

I "draw" my board layout's in Excel. For matrix boards, the layout is as seen from the back, I then just have to connect all of the points with the same name. Pretty much all the wiring on the rom board is either edge connector to chip or chip to chip. The power connections do visit multip...

Elsewhere http://www.mtxworld.dk/memorum/viewtopic.php?f=9&t=419 I've mentioned building a board to test a black screening MTX. Rather than drag that thread off topic I've started a new one. The board itself is basically just 2 chips and some configuration jumpers. There's a 32k or larger (e)epr...

The wiring on the diagnostic rom board is complete, as is a candidate version of the GAL. The next step is to get a test rom written that will run without using the main ram, but will test it. I've got some video routines working in emulation, once I've got a bit more I'll put together a test image ...

ROM Pin 1 is +5VDC - perhaps you grounded it by mistake and blew something in the power circuit? If you're lucky, it might just be a cap or something, if you're very unlucky, you might have melted a track, either way, the machine can probably be saved, don't bin it just yet I'd echo Dave's comments...

I've chopped up a bit of scrap matrix board and added a 32 pin and 20 pin socket plus some jumpers. to come up with this mock up: rom board idea.jpg A 20 pin 16V8 GAL or CPLD has more than enough capacity to allow for paging in 4 different rom Images from a 32k, 28 pin EPROM or EEPROM. However EPROM...

Unless someone has some pulls from a dead MTX, the only solution I'm aware of for broken roms, is to replace the with EPROM or EEPROM. But that's a one way trip as it means cutting tracks details of how Dave fixed one of his are here: http://primrosebank.net/computers/mtx/repairs/rom/mtx_rom_replace...

Address lines A0-A6 show activity, A7-15 do not. Could this be just the ROM start-up code getting so far within the first 256 bytes before crashing and restarting? But then I should see data on the data bus and I don't. (Well, I often see one edge and sometimes see multiple data on some data lines ...