Search found 116 matches

by stephen_usher
Fri Apr 03, 2020 11:59 am
Forum: off-topic
Topic: Which retro calculator is best?
Replies: 29
Views: 677

Re: Which retro calculator is best?

My Casio fx-2500 (bought February 1979) got me through my 'O' Levels and still works nicely.
IMG_0903.jpg
by stephen_usher
Thu Mar 26, 2020 4:01 pm
Forum: general
Topic: Today I received.....
Replies: 5714
Views: 492607

Re: Today I received.....

I think a lot of these will be arriving today... ZX Spectrum Next accelerated... Nice :-) I would have like one, but I missed the boat on the Kickstarter. I am a backer of the Atari VCS console though, but don't know when that's likely to arrive. Second Kickstarter will hopefully start directly aft...
by stephen_usher
Thu Mar 26, 2020 1:44 pm
Forum: general
Topic: Today I received.....
Replies: 5714
Views: 492607

Re: Today I received.....

I think a lot of these will be arriving today... ZX Spectrum Next accelerated...
IMG_1827.jpg
by stephen_usher
Fri Mar 20, 2020 6:46 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

My goodness! Looks good.
by stephen_usher
Sat Mar 14, 2020 11:18 am
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

That's still cool enough to keep your finger on it without getting uncomfortable. Maybe no-one else has measure the temperature.

Anyway, I was being cautious, given that there are no replacements available.
by stephen_usher
Fri Mar 13, 2020 10:27 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

Have you put a heat sink on the ARM? It may need it at that clock rate. It was getting above 60C at 72MHz.
by stephen_usher
Thu Mar 12, 2020 9:53 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

I wanted to keep to multiples of 24MHz. I would guess that if a 48MHz crystal was 9.64 Mips then a 50MHz one would pretty well hit it. (Doing the calculation, it should be a 49.793MHz oscillator, but they don't exist.)
by stephen_usher
Thu Mar 12, 2020 6:02 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

OK, here are some useful timings:

Boot to desktop (Uniboot):
  • Stock: 1 minute 41 seconds
  • 48MHz: 1 minute 28 seconds (1.15x faster)
  • 72MHz: 56 seconds (1.8x faster)
The 48MHz crystal gives 9.64 Mips according to Si3
by stephen_usher
Thu Mar 12, 2020 5:49 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

48MHz test: Interesting result.

The 48MHz crystal oscillator arrived today and I've just done a quick test. Everything works other than 50Hz low bandwidth modes. Low bandwidth modes fail as with the higher clocked overclocking BUT have fewer repeats across the screen. So, it looks like for at least some of the video modes the syst...
by stephen_usher
Wed Mar 11, 2020 6:56 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

Well, decreasing the lead length is a good idea as at high frequencies the wires are more wave guides than conductors. This is why I still had scrambled Mode 33 video even when the resistor was only connected to the 72MHz output. Reducing the wire length changed the effect. An SMD resistor would be ...
by stephen_usher
Wed Mar 11, 2020 6:31 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

Could you post a photo of your oscillator socket and the resistor you’ve added? Note: my machine is an A4000 so slightly different to the A3010/A3020 where the space for the resistor (R10) is in a slightly different place. The socket is a normal 14 pin socket with all but 6 pins removed from undern...
by stephen_usher
Tue Mar 10, 2020 6:19 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

vanpeebles wrote:
Tue Mar 10, 2020 12:05 pm
Double the MIPS does seem a like a fierce overclock. I hope you boys won't ride the tail off these old A3010s.
I may get a 48MHz oscillator and see how that goes. They're cheap so it's not a problem to experiment.
by stephen_usher
Tue Mar 10, 2020 5:52 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

OK, I've fitted the 72MHz oscillator and run some tests: The system seems stable Mode 33 (and other 2 colour modes) are scrambled Si shows the speed to be seemingly marginally slower than when using the video 72MHz oscillator... But Zarch seems to run a lot faster and the demo runs slightly differen...
by stephen_usher
Mon Mar 09, 2020 10:49 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

What would be a nice overclock of say around 10 to 11 mips? I'm guessing around 50MHz. To be honest I don't understand why the clockrate of the processor is 1/3rd of the X100 oscillator or how it disables the 25MHz clock. I'm also surprised that the 75MHz oscillator caused the VIDC to mess up its t...
by stephen_usher
Mon Mar 09, 2020 6:02 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

The 75MHz crystal oscillator arrived today so I thought I'd test it, not expecting the machine to boot, but it did... IMG_1808.jpg IMG_1809.jpg IMG_1810.jpg IMG_1811.jpg However, the machine isn't very stable, it locked up after a few seconds of the Zarch demo running and the "Mode 33" corrupt displ...
by stephen_usher
Sun Mar 08, 2020 8:55 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

Sure, I'll probably make a new post as my machine's an A4000 rather than an A3010.

Are you using the video 72MHz oscillator to overclock?

We'll see later this week when the 72MHz oscillator for the X100 location arrives if the machine is stable with two separate clocks, which may be out of phase.
by stephen_usher
Sun Mar 08, 2020 10:46 am
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

OK, now confirmed. Shortening the lead length of the resistor on the oscillator side allows the mode to be changed correctly. If the other end is connected to the "R10" pad then the mode change fails. Time to get a 72MHz crystal oscillator and a surface mount 22R resistor for the X100 socket. P.S. R...
by stephen_usher
Sun Mar 08, 2020 10:33 am
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

I think I have tied it down to the overclocking, or rather the 22R resistor connected to the 72MHz oscillator. If I have the resistor connected to the oscillator pad (but not connected to the other end) then the mode change fails. If I have it connected at the other end and not at the oscillator all...
by stephen_usher
Sun Mar 08, 2020 10:18 am
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

OK, this morning's test: Try to revert to stock. Unfortunately, after removing the new RAM the contacts on the ZIP connectors have been opened too much to allow the original RAM to work. However, I tested with the on-board 2MB and "Mode 33" worked. I then re-fitted the new RAM and... Mode 33 worked....
by stephen_usher
Sat Mar 07, 2020 10:38 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

I'm booting straight to the desktop ("No Boot" and "*OPT 4,0"), running Apps->Configure and then changing the screen resolution. I can even do this without the IDE disk connected if you like.

Update: Which I just have and done a hard reset.
by stephen_usher
Sat Mar 07, 2020 10:22 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

I'm not auto booting from the disk, this is just running the ROM, so no ADFFS. I've discovered that none of the monochrome screen modes seem to work. The video memory format is switched correctly but it seems that the video controller doesn't change, as can be seen by the colour (and correct) mouse ...
by stephen_usher
Sat Mar 07, 2020 10:11 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

Also, switch to "Mode 33" on the desktop and...
IMG_1807.jpg
by stephen_usher
Sat Mar 07, 2020 10:02 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

My A4000 was already 4MB.

It's not only this game but to a lesser extent Lemmings and "Oh No More Lemmings" (screen after they end) and during the loading stage of "Cannon Fodder"
by stephen_usher
Sat Mar 07, 2020 10:01 pm
Forum: general
Topic: Things I haven’t received yet...
Replies: 13
Views: 567

Re: Things I haven’t received yet...

Pi Zeros are basically out of stock everywhere (except one place in Italy with a small amount of stock and one or two places in the USA), maybe this is the problem? Apparently the Pi Zero and Zero W are fillers for the production line when other Pis are not in production. Unfortunately the Pi4 has b...
by stephen_usher
Sat Mar 07, 2020 9:52 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

Most games I've tried work well, even Pacmania did every time but the first.

Zarch, however, is just too fast! https://youtu.be/y6oBkZMdLRs
by stephen_usher
Sat Mar 07, 2020 9:40 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: Today I overclocked my A3010

It did on my machine.

Here's a video of the issue.

https://youtu.be/3rtRru9sQNs

I'm wondering if it's a video DMA problem with certain video modes.
by stephen_usher
Sat Mar 07, 2020 4:30 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: For Sale: A3020/A4000 & A5000 overclockable RAM

After much testing the machine mostly operates correctly and stably. However, the machine can't display certain display modes correctly and merely outputs a scrambled mess, as if the output is the wrong mode for the data in the memory, e.g. Mode 49. A good test for this is to get the "!Blue" (Blue T...
by stephen_usher
Sat Mar 07, 2020 3:11 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: For Sale: A3020/A4000 & A5000 overclockable RAM

For reference, this is the output from !ARMSi 3:
2020030715162879.png
by stephen_usher
Sat Mar 07, 2020 1:45 pm
Forum: hardware
Topic: Today I overclocked my A3010
Replies: 427
Views: 36172

Re: For Sale: A3020/A4000 & A5000 overclockable RAM

The RAM is installed and working. To help fitting I opened up the contacts on the ZIP memory connections by poking an oscilloscope probe into each one in turn, pushing back the contacts slightly. The modules then slipped in with only moderate force required. I also experimented with overclocking by ...
by stephen_usher
Sat Mar 07, 2020 1:11 pm
Forum: hardware
Topic: Open source A3020 RAM
Replies: 57
Views: 3083

Overclocking.

After the conversation last night I've fitted a 22 ohm resistor between the 72MHz oscillator output to the CPU pad side of R10 and...

It works!

Zarch runs a bit quick!!!

But Pacmaina runs really slowly.

So, some things don't like the timings.