Search found 3122 matches

by 1024MAK
Sun Apr 21, 2024 3:03 pm
Forum: Programming
Topic: Goodbye,Z80
Replies: 25
Views: 967

Re: Goodbye,Z80

Morkin wrote: Fri Apr 19, 2024 12:18 pm Well, that's that then.

See you guys on the Amiga forums...
Good luck finding a brand new 68000 MPU...

Mark
by 1024MAK
Sun Apr 21, 2024 3:02 pm
Forum: Programming
Topic: Goodbye,Z80
Replies: 25
Views: 967

Re: Goodbye,Z80

What does it exactly mean? Brand new Z80 MPUs and the support chips for it that were still available will no longer be manufactured. Yes, there are plenty of used Z80 MPUs on the grey market. But as with many things on the grey market (including trading sites like eBay) what you actually get may no...
by 1024MAK
Sun Apr 21, 2024 2:45 pm
Forum: Hardware
Topic: black plus 2 keyboard fault
Replies: 6
Views: 194

Re: black plus 2 keyboard fault

And if course, the joystick ports are part of the same matrix...

Glad you found the problem :D

Mark
by 1024MAK
Sat Apr 20, 2024 9:36 am
Forum: Website
Topic: "Most users..."
Replies: 7
Views: 635

Re: "Most users..."

Currently:
In total there are 292 users online :: 12 registered, 0 hidden and 280 guests (based on users active over the past 15 minutes)
Most users ever online was 1411 on Tue 19th Mar 2024 09:18
Mark
by 1024MAK
Thu Apr 18, 2024 2:51 pm
Forum: Hardware
Topic: Timex Sinclair 2040 printer question
Replies: 5
Views: 141

Re: Timex Sinclair 2040 printer question

This printer needs a PSU with a 24V 1A AC output.

Mark
by 1024MAK
Thu Apr 18, 2024 2:46 pm
Forum: Hardware
Topic: black plus 2 keyboard fault
Replies: 6
Views: 194

Re: black plus 2 keyboard fault

Okay, that's weird... The keyboard matrix is pure hardware and what program is running shouldn't make any difference to the hardware. Having said that, BASIC and some games will ignore a key if two of the normal keys are detected to be pressed simultaneously. That may explain why the symptoms are di...
by 1024MAK
Thu Apr 18, 2024 2:26 pm
Forum: Hardware
Topic: DC-DC mod query
Replies: 5
Views: 205

Re: DC-DC mod query

So, over the lifetime of the Spectrum, there were various changes to the circuitry including that of the DC-DC converter section. The website/blog you linked to is mine BTW. On your board, you may have either an earlier version or it has just been implemented differently. The service technicians tha...
by 1024MAK
Tue Apr 16, 2024 2:16 pm
Forum: Hardware
Topic: black plus 2 keyboard fault
Replies: 6
Views: 194

Re: black plus 2 keyboard fault

It may be that the problems with the keyboard existed before you opened the case. Were you able to test it before opening it? The keyboard uses a membrane, which itself is wired as a matrix of "switches". The "normal" keys (those that are the same as in a rubber key model) use a ...
by 1024MAK
Mon Apr 15, 2024 9:11 am
Forum: Hardware
Topic: +2B with a non responsive keyboard
Replies: 37
Views: 5533

Re: +2B with a non responsive keyboard

With faults, I much prefer members to start a new topic. This saves confusion. However, I'm not an admin or moderator here.

Mark
by 1024MAK
Mon Apr 08, 2024 5:26 pm
Forum: Programming
Topic: Bank switching issue
Replies: 32
Views: 1087

Re: Bank switching issue

So, just the few instructions needed to switch banks then I guess? I was expecting a bigger speed penalty to bank switching. The latch chip that stores the extra address bits for the memory is just as quick as the Z80. The limiting factors are what you have to do in your software routine and the OU...
by 1024MAK
Sun Apr 07, 2024 10:40 am
Forum: Hardware
Topic: Question about 48K composite mod
Replies: 5
Views: 250

Re: Question about 48K composite mod

I assume you were using an original Sinclair power supply unit (model UK1400 9V 1.4A). This is not a universal mains voltage type, as it requires a nominal 240V AC 50Hz mains input voltage. It will not produce enough output voltage if connected to a 110V – 120V 60Hz mains supply. The good news is th...
by 1024MAK
Sat Apr 06, 2024 1:53 pm
Forum: Hardware
Topic: Question about 48K composite mod
Replies: 5
Views: 250

Re: Question about 48K composite mod

Yes, it has definitely been modified. The (phono) output connector on the modulator (what was the UHF TV output) will now output a composite video signal. I can't tell which version (there are more than four...) of the composite video modification has been done. If you want to know, you need to care...
by 1024MAK
Tue Apr 02, 2024 9:49 pm
Forum: Hardware
Topic: Hardware diagnostics interface (Pico based)
Replies: 4
Views: 185

Re: Hardware diagnostics interface (Pico based)

Oh, and during the RAM check that the ROM does, it may be possible to check for some RAM faults that the ROM code does not test for. It's not possible to pick up all RAM faults, because the intention of the ROM routine is to simply work out how much RAM is fitted, NOT if it works correctly. Hence th...
by 1024MAK
Tue Apr 02, 2024 9:45 pm
Forum: Hardware
Topic: Hardware diagnostics interface (Pico based)
Replies: 4
Views: 185

Re: Hardware diagnostics interface (Pico based)

Nice 8-) The next step would be an instruction trace, Often knowing at what point the Z80 is no longer executing the expected sequence can help identify the problem, or at least narrow it down. If there is no input from the user, the machine should make it to the "copyright" screen with th...
by 1024MAK
Tue Apr 02, 2024 5:33 pm
Forum: Programming
Topic: Bank switching issue
Replies: 32
Views: 1087

Re: Bank switching issue

It's called bank switching or paging, but at the hardware level, the value on the data bus from the OUT is stored in a latch (register). Then some of the bits are used as extra address lines to the memory (ROM and RAM). The effect of this is that as described above, the Z80 can only see a "wind...
by 1024MAK
Sun Mar 31, 2024 8:49 pm
Forum: Programming
Topic: Zilog's Z80 opcode choice
Replies: 20
Views: 518

Re: Zilog's Z80 opcode choice

CP/M became a big thing and certainly helped make the Z80 successful. I don't know if during the design of the Z80 CP/M was considered. But it may have been. As far as I can recall, the 6502 did not have a direct equivalent to CP/M back then. There was FLEX for the 6800, and then later on a version ...
by 1024MAK
Sun Mar 31, 2024 4:37 pm
Forum: Programming
Topic: Zilog's Z80 opcode choice
Replies: 20
Views: 518

Re: Zilog's Z80 opcode choice

To be fair, the 6809 came along a lot later, and because it was late to the party, and hence not established (so not as cheap) only made it into a small number of computer models.

Yes, it was a good and powerful microprocessor.

Mark
by 1024MAK
Sun Mar 31, 2024 7:34 am
Forum: Programming
Topic: Zilog's Z80 opcode choice
Replies: 20
Views: 518

Re: Zilog's Z80 opcode choice

This is probably more of a general Z80 question rather than applying to the Spectrum specifically, but do you think when Zilog designed and implemented the Z80's instructions and assigned them to either 1 or more byte opcodes that they always made the right choice? I'm not really talking about hypo...
by 1024MAK
Wed Mar 13, 2024 11:13 pm
Forum: ZX80 & ZX81
Topic: WRX True High Resolution Graphics
Replies: 5
Views: 796

Re: WRX True High Resolution Graphics

For the game, see also
https://www.sinclairzxworld.com/viewtop ... f=11&t=289
and
https://www.sinclairzxworld.com/viewtop ... f=4&t=1317

For the details on how hires works, this site is a bit more readable (apart from the ASCII diagrams) ;-)

Mark
by 1024MAK
Sun Mar 10, 2024 2:23 pm
Forum: Hardware
Topic: When tapes fail due to age
Replies: 9
Views: 471

Re: When tapes fail due to age

Sounds like a lack of volume issue.

Mark
by 1024MAK
Tue Mar 05, 2024 2:12 pm
Forum: Hardware
Topic: very low 'volume' from 'speaker'
Replies: 6
Views: 188

Re: very low 'volume' from 'speaker'

That's diode D13 (1N4148).

Speakers unless the cone is damaged, either work normally or are completely broken.

Mark
by 1024MAK
Thu Feb 29, 2024 3:31 pm
Forum: Hardware
Topic: New open lower RAM module design (photoessay)
Replies: 98
Views: 2778

Re: New open lower RAM module design (photoessay)

And the last part of that post appears to have got lost. It should have ended:

'It will be hard to work out exactly what the problem is".

Mark
by 1024MAK
Wed Feb 28, 2024 8:25 pm
Forum: Hardware
Topic: New open lower RAM module design (photoessay)
Replies: 98
Views: 2778

Re: New open lower RAM module design (photoessay)

Okay, best if we calm down. Right, so there are some points I want to comment on. First off, we now know far more about how high speed digital signals are affected on PCBs now, compared to the 1980s. And Sinclair did have problems. Yes, the ZX Spectrum was okay, but the QL board had to be redesigned...
by 1024MAK
Sat Feb 24, 2024 2:50 pm
Forum: Hardware
Topic: Question... 2nd joystick button?
Replies: 9
Views: 260

Re: Question... 2nd joystick button?

I'm curious to know whether the Spectrum can make use of a 2nd joystick button (or Master System pad buttons for example)? As Andy says, it depends on the actual joystick interface. By this, I mean both the type and the actual revision/version. This is especially relevant for Kempston or Kempston c...
by 1024MAK
Fri Feb 23, 2024 7:26 pm
Forum: Hardware
Topic: Composite to Scart - What am i doing wrong
Replies: 8
Views: 244

Re: Composite to Scart - What am i doing wrong

You might be able to fit a composite connector to that monitor, it has markings for cvbs input, on a lot of those rebadged Philips (cm8833) monitors you can. Will not help if it lacks the PAL colour decoder circuitry... Does scart need voltage for it to switch? "Notice the +5 volts applied to ...