https://www.qlforum.co.uk/
Plus various QL web sites.
Mark
Search found 3124 matches
- Wed May 01, 2024 11:34 am
- Forum: Website
- Topic: Did I mention the search is bad?
- Replies: 11
- Views: 385
- Mon Apr 22, 2024 12:59 pm
- Forum: Programming
- Topic: Goodbye,Z80
- Replies: 33
- Views: 1646
- Sun Apr 21, 2024 3:03 pm
- Forum: Programming
- Topic: Goodbye,Z80
- Replies: 33
- Views: 1646
- Sun Apr 21, 2024 3:02 pm
- Forum: Programming
- Topic: Goodbye,Z80
- Replies: 33
- Views: 1646
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...
- Sun Apr 21, 2024 2:45 pm
- Forum: Hardware
- Topic: black plus 2 keyboard fault
- Replies: 6
- Views: 280
Re: black plus 2 keyboard fault
And if course, the joystick ports are part of the same matrix...
Glad you found the problem
Mark
Glad you found the problem
Mark
- Sat Apr 20, 2024 9:36 am
- Forum: Website
- Topic: "Most users..."
- Replies: 7
- Views: 958
Re: "Most users..."
Currently:
MarkIn 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
- Thu Apr 18, 2024 2:51 pm
- Forum: Hardware
- Topic: Timex Sinclair 2040 printer question
- Replies: 5
- Views: 179
Re: Timex Sinclair 2040 printer question
This printer needs a PSU with a 24V 1A AC output.
Mark
Mark
- Thu Apr 18, 2024 2:46 pm
- Forum: Hardware
- Topic: black plus 2 keyboard fault
- Replies: 6
- Views: 280
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...
- Thu Apr 18, 2024 2:26 pm
- Forum: Hardware
- Topic: DC-DC mod query
- Replies: 6
- Views: 321
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...
- Tue Apr 16, 2024 2:16 pm
- Forum: Hardware
- Topic: black plus 2 keyboard fault
- Replies: 6
- Views: 280
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 ...
- Mon Apr 15, 2024 9:11 am
- Forum: Hardware
- Topic: +2B with a non responsive keyboard
- Replies: 37
- Views: 5582
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
Mark
- Mon Apr 08, 2024 5:26 pm
- Forum: Programming
- Topic: Bank switching issue
- Replies: 32
- Views: 1162
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...
- Sun Apr 07, 2024 10:40 am
- Forum: Hardware
- Topic: Question about 48K composite mod
- Replies: 5
- Views: 273
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...
- Sat Apr 06, 2024 1:53 pm
- Forum: Hardware
- Topic: Question about 48K composite mod
- Replies: 5
- Views: 273
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...
- Tue Apr 02, 2024 9:49 pm
- Forum: Hardware
- Topic: Hardware diagnostics interface (Pico based)
- Replies: 4
- Views: 201
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...
- Tue Apr 02, 2024 9:45 pm
- Forum: Hardware
- Topic: Hardware diagnostics interface (Pico based)
- Replies: 4
- Views: 201
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...
- Tue Apr 02, 2024 5:33 pm
- Forum: Programming
- Topic: Bank switching issue
- Replies: 32
- Views: 1162
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...
- Sun Mar 31, 2024 8:49 pm
- Forum: Programming
- Topic: Zilog's Z80 opcode choice
- Replies: 20
- Views: 554
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 ...
- Sun Mar 31, 2024 4:37 pm
- Forum: Programming
- Topic: Zilog's Z80 opcode choice
- Replies: 20
- Views: 554
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
Yes, it was a good and powerful microprocessor.
Mark
- Sun Mar 31, 2024 7:34 am
- Forum: Programming
- Topic: Zilog's Z80 opcode choice
- Replies: 20
- Views: 554
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...
- Wed Mar 13, 2024 11:13 pm
- Forum: ZX80 & ZX81
- Topic: WRX True High Resolution Graphics
- Replies: 5
- Views: 1325
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
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
- Sun Mar 10, 2024 2:23 pm
- Forum: Hardware
- Topic: When tapes fail due to age
- Replies: 9
- Views: 802
Re: When tapes fail due to age
Sounds like a lack of volume issue.
Mark
Mark
- Tue Mar 05, 2024 2:12 pm
- Forum: Hardware
- Topic: very low 'volume' from 'speaker'
- Replies: 6
- Views: 474
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
Speakers unless the cone is damaged, either work normally or are completely broken.
Mark
- Thu Feb 29, 2024 3:31 pm
- Forum: Hardware
- Topic: New open lower RAM module design (photoessay)
- Replies: 98
- Views: 3518
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
'It will be hard to work out exactly what the problem is".
Mark
- Wed Feb 28, 2024 8:25 pm
- Forum: Hardware
- Topic: New open lower RAM module design (photoessay)
- Replies: 98
- Views: 3518
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...