Search found 807 matches

by Pr0f
Tue May 04, 2021 10:31 am
Forum: Hardware
Topic: Tetroid Disc Interface and Flp1_
Replies: 18
Views: 899

Re: Tetroid Disc Interface and Flp1_

The idea of the strain relief 'loop' is to take the force when you yank on the ribbon cable to free the connector from it's socket - otherwise you are more than likely to pull the ribbon cable off the plug contacts when yanking it... I always liked the sockets with the little levers on each side whi...
by Pr0f
Wed Apr 28, 2021 12:34 pm
Forum: Software & Programming
Topic: Game score
Replies: 4
Views: 254

Re: Game score

almost like a root mean squared value of tries / grids to give a value of between 0 and 1, where 1 would give 100, and higher values of tries would tend towards 0 so 100 * sqrt ((1/tries) * gridsize^2) for gridsize of 5, with 25 tries that would give 100 For gridsize of 5 with 50 tries that would gi...
by Pr0f
Sat Apr 24, 2021 11:04 pm
Forum: The Off-Topic Section
Topic: Happy Birthday!
Replies: 317
Views: 98924

Re: Happy Birthday!

That's a goodly selection of ales ! :-) :D
by Pr0f
Sat Apr 24, 2021 4:17 pm
Forum: The Off-Topic Section
Topic: Happy Birthday!
Replies: 317
Views: 98924

Re: Happy Birthday!

Happy Birthday Van Peebles - any fun things arrive?
by Pr0f
Thu Apr 15, 2021 8:17 am
Forum: Hardware
Topic: Question about a non-working ZX Spectrum
Replies: 31
Views: 1660

Re: Question about a non-working ZX Spectrum

I would say the issue is more likely on the RAM/ULA side of the address lines or data lines and not so likely to be on the CPU/ROM side of those lines. Between the multiplexer chips (157) and the dram chips - you will notice that the address lines have a resistor between. And in a similar way, the C...
by Pr0f
Tue Apr 13, 2021 10:16 pm
Forum: Hardware
Topic: Question about a non-working ZX Spectrum
Replies: 31
Views: 1660

Re: Question about a non-working ZX Spectrum

I think it is a fix for IORQGE - as that signal wasn't good from the ULA for some batches - but it's been some time since I've looked at the old boards
by Pr0f
Tue Apr 13, 2021 9:22 am
Forum: Hardware
Topic: 68K-MBC
Replies: 13
Views: 675

Re: 68K-MBC

I don't get the impression he was ever aiming to make a QL - just a minimal chip count 68K based computer - so goal achieved.
by Pr0f
Tue Apr 13, 2021 9:13 am
Forum: Hardware
Topic: Question about a non-working ZX Spectrum
Replies: 31
Views: 1660

Re: Question about a non-working ZX Spectrum

Testing the RAM chips is a good idea, but only tells you the RAM chips are working - if the issue lies on the board itself, then you won't see the fault with the RAM chip out of the spectrum.

Power supplies, glue logic, even just something stuck on the PCB could cause the issue.
by Pr0f
Mon Apr 12, 2021 9:37 pm
Forum: Hardware
Topic: Question about a non-working ZX Spectrum
Replies: 31
Views: 1660

Re: Question about a non-working ZX Spectrum

If it's processing through the ROM then yes. What you really want is a plug in cartridge or similar that has it's own ROM in it - see if that gives a legible display. There is a good diagnostic ROM for the spectrum (well actually several), that will attempt to test cpu, memory, screen etc. This will...
by Pr0f
Mon Apr 12, 2021 9:14 pm
Forum: Hardware
Topic: 68K-MBC
Replies: 13
Views: 675

Re: 68K-MBC

I wonder why they went for a 68008 instead of a 68000 ? It was a screwup and mismanagement. Clive thought he could do QL with 64K RAM as a fot in the door and with substantially cheaper 68008. But when it came out, 68008 was _more_expensive than 68000. Also, 128K in QL used 16 DRAM chips. And as it...