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

It should already boot as 18. But probably will also have C and maybe F configured I can't remember. But if it isn't, booting into CPM with return held down bypasses the disc boot and runs the monitor instead, from that command prompt type BB18 And that should boot off the B drive configured as type...

You just could try it! Grab the Rememotech distribution package from Andy's website. Write the SDdisc.Bin package to your 4 meg card with a imaging program Configure it as a type 18 drive but don't fill more than half of it. It might work. CPM has very simple allocation rules and just uses the first...

Is there anything in that one that's not in the last dozen or so pages of the FDX technical manual ?

The address decoding is 90% done in the PAL/GAL so that ought to be testable in the programmer.

The last 10% being done by the 74LS00 at J10 selects between rom B and rom C if the page roms are active.

A couple of thoughts: The change at 9D looks like someone's done the timing chain mod from page 47 of the service manual, R32 and R33 look to have ben replaced, you can only see one of them in the photo, but the wrong colours for a 560R. R35 and R36 have been pulled as per the mod. The CMOS chip's d...

Test rom updated to build 245. the Ram test has been expanded to stop on read failure with a brief diagnostic as shown on this screen dump from the emulator. Since the emulator never actually fails the read back, this is actually fake, :D but it looks better than a photo of my 1980's green screen mo...

If you're going with a high pin count CPLD, then that means working at 3.3v instead of 5v. Rather than invest in a mass of level shifting to accommodate a Z80, the low power version of the Z180 might be an easier fit. The Z8S180 has 20mhz 3.3v version. For an idea of resource cost, I've VHDL code fo...

If you're building a system that can't use PS2 or USB, then the cost of the keyboard components is possibly the biggest outlay. Buying from Mouser in packs of 100, a 12mm key and keycap works out at 60.6p each. With anywhere between 40 (ZX81, Spectrum) and 80 (MTX/MSX/SAM) in a home brew, that can b...

The memory test could be re-written to stop at a failed read back, and then print something along the lines of "Value read :XX value expected :XX". at which point the test would have to stop. I don't think there's enough registers to do much more than that. Re-starting and only halting once the scre...

Crazyboss wrote: ↑

20 May 2019 15:32

If its Cambridge, I looks like there is an airport nearby, but its seems like its closed, at least its not possible to fly there from Copenhagen

Try flights to and from London Stanstead - that's got a direct train to Cambridge, takes about half an hour according to the time table.