Search found 1858 matches

by RobC
Sat Jan 20, 2018 7:02 pm
Forum: hardware
Topic: Beeb FPGA
Replies: 476
Views: 27999

Re: Beeb FPGA

I've had a go at the Speccy mode now. Here's a sample screen I converted coming out of the VideoNuLA in BeebFpga: Great stuff =D> Rob, the only thing I wasn't sure about was the packing of the 4-bit foreground and background colour in the attribute byte. Which way around are they? At the moment, I'...
by RobC
Sat Jan 20, 2018 8:46 am
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

I have one of these for my Spectrum. And it is awesome - emulator quality output! I believe it works by ‘listening’ for writes to the screen RAM in order to produce its picture but am not 100% sure. http://www.fruitcake.plus.com/Sinclair/ ... erface.htm Thanks - I'd not seen that before. It's a gre...
by RobC
Fri Jan 19, 2018 9:46 am
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

The issue is that we want to ensure that actual screen writes on the host are done at the same raster position as emulated screen writes. My idea is to set up a free-run VIA timer set to interrupt every 4 scanlines (256us); all the interrupt does is increment a counter (which is reset on VSync). No...
by RobC
Thu Jan 18, 2018 9:47 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

I would think that your flicker is mostly caused by not syncing VSyncs on the host with your emulated HALT on the parasite. I would expect most games to use that to avoid flicker as much as possible, even those which have to present the back buffer via the SP or unrolled LDI techniques (as this can...
by RobC
Thu Jan 18, 2018 9:12 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Thanks Rich - that's really useful. I've read a little bit on Spectrum games but don't really do Z80 so it's all new to me. At the moment, I'm just running a set number of t-states per frame (~70,000) and then doing the host stuff with wait for vsync in the screen refresh. So, the Z80 core is effect...
by RobC
Thu Jan 18, 2018 8:34 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Which issue is that? The only difference is that the Master keyboard has 16* columns to the Beeb's 10 columns. (*ok, technically 13 columns) The Master always returns the lowest key found provided it's greater than the start key given in X (as described in the Master reference manual). So, I was ch...
by RobC
Thu Jan 18, 2018 7:25 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Hi Dave, Is there any possibility you could save a sample screen of a game running on the emulator? Sure - I'll just have to add a function to dump out the video memory and attributes. It'll probably not be until tomorrow though as I'm looking at speeding up the keyboard handling tonight. (Annoyingl...
by RobC
Thu Jan 18, 2018 4:15 pm
Forum: hardware
Topic: Large project box
Replies: 5
Views: 231

Re: Large project box

in the early days you had ( it think it was from sideway) a metal box , with open space for flatcable to beec what was covered with a half metal box with holes for two drisk drives. maybe they are still around in uk ? or make something like that. from metal ? I think I've got a couple of these some...
by RobC
Thu Jan 18, 2018 10:04 am
Forum: hardware
Topic: Acorn Z80 manuals
Replies: 1
Views: 121

Re: Acorn Z80 manuals

Thanks for this - it's great to have them scanned.
by RobC
Thu Jan 18, 2018 8:44 am
Forum: hardware
Topic: Newbie question regarding first machine
Replies: 16
Views: 436

Re: Newbie question regarding first machine

I'd go for a B or a Master as a first machine. The B+ and Compact tend to be much harder to find and so are more expensive. From an interface/peripheral perspective, the B, B+ and Master are very similar (apart from the speech chip and cartridge port) so you could try running the different machines ...
by RobC
Tue Jan 16, 2018 8:42 am
Forum: for sale / freebies
Topic: VideoNuLA boards
Replies: 43
Views: 3781

Re: VideoNuLA boards

Has anybody used the nULA board in a Master Compact? I have one in my Compact and it fits without any problems as long as you don't have an Econet module fitted. However, mine doesn't have a floppy inside the case so I don't know if it'll fit in yours. I keep meaning to try putting VideoNuLA at the...
by RobC
Sun Jan 14, 2018 9:57 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Batman the movie Beach buggy simulator More tea vicar (lots of particles) Repton 1 and 2 ported by Gil who wrote Jeltron with me in the 80s. No scrolling, but what does bomb Jack look like ;) Thanks tricky. Haven't tried Bomb Jack yet but I played the Spectrum version on an emulator when I was look...
by RobC
Sun Jan 14, 2018 7:18 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

A good *test* would be running z80 BBC basic for the spectrum on it. Great idea - I'll try it as soon as I can. The emulator can only load snapshots at the moment but I can add ROM loading. This looks really cool! Waiting patiently for the release. Can we update VideoNula ourselves, or do we have t...
by RobC
Sun Jan 14, 2018 4:32 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

mlouka wrote:When trying out your ZX81 emulator, I ended up using a real ZX81 as a "keystrip"!

Good idea :D I've now setup my Spectrum next to the Beeb!
by RobC
Sun Jan 14, 2018 10:25 am
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Wow, wow and wow! From pun to reality in a very short period of time. Amazing! Thanks - the idea was all yours though :) . Progressing from the ZX81->Jupiter Ace->Spectrum helped. When will I be able to play Bards Tale? I'm going to try to get something usable out in the next week or so. I'm also h...
by RobC
Sat Jan 13, 2018 10:16 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

This looks really cool. Thanks Dave - it wouldn't be possible without the Pi co-pro :D It's a lot of fun running a Spectrum on my Beeb but I'd forgotten just how many keywords were crammed onto the keys and it's really hard when the keys only have the letters on them. However, my six-year-old daugh...
by RobC
Sat Jan 13, 2018 6:11 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

crj wrote:If you're writing to the tube from emulated hardware, i.e. directly within the PiTubeDirect code, maybe you can be certain of keeping the FIFO from becoming empty? If so, you could go a little faster by not polling the status register.

Good point - I'll give it a go...
by RobC
Sat Jan 13, 2018 5:54 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

If you are going to hack around in OSWRCH, isn't it more efficient to keep a copy of screen memory on the Parasite and send actual values rather than values to EOR, by the way? This is how I do it with my emulators (ZX81, Ace and Spectrum). I've now implemented the equivalent of hoglet's OSWRCH mec...
by RobC
Sat Jan 13, 2018 4:34 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Isn't the defined - and quickest - way to do this stuff for the Parasite to provoke the Host into initiating a memory transfer? 256-byte blocks can be transmitted at the rate of 100Kbytes per second, because of the reduced handshaking overheads. And the Beeb end can do what it wants with each byte ...
by RobC
Sat Jan 13, 2018 3:35 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Whereas the full VDU handler presumably has overhead, once the new handler sees an FF it starts to pull data directly from the Tube chip - and as it's host side, that's a fairly justifiable thing to do. Overall, the full VDU stack penalty is paid once per screen. Many thanks for that - I understand...
by RobC
Sat Jan 13, 2018 2:28 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

As the copro runs ridiculously fast, overhead on that side of the Tube mightn't amount to much - I'd guess overhead on the host side is the case to worry about. But it might well be better to experiment than to theorise... Yes - I wanted to avoid handling lots of calls on the host. I think there pr...
by RobC
Sat Jan 13, 2018 12:56 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Interesting... I just checked to see how Dave managed to extend the Tube protocol for the second processor Life. It turns out - and now I do remember this - he extends the VDU protocol. Thanks for that Ed - I hadn't seen it so it was interesting to look through the code. I chose to extend OSWORD so...
by RobC
Sat Jan 13, 2018 8:50 am
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Is the Pi fast enough to look for small areas of shifted/scrolled graphics and send a scroll command for an area? I would think so. My current screen refresh routine is very simple as it just sends the address and value for every byte of pixel data that needs to change as a set of triplets. Attribu...
by RobC
Fri Jan 12, 2018 10:30 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

Re: SpectROM - Speccy emulator for the Pi co-pro

Thanks for the encouragement. Will this require the VideoNuLA or will it run without with “interesting” colours? It needs VideoNuLA, as apart from the colours, it uses a new attribute mode that's able to mimic the Spectrum's display. I had to modify the VideoNuLA VHDL to implement this so there's cu...
by RobC
Fri Jan 12, 2018 4:52 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 54
Views: 1279

SpectROM - Speccy emulator for the Pi co-pro

Following Lardo's suggestion in the ZX81 emulator thread, I decided to have a go at a ZX Spectrum emulator. After a lot of squeezing of code, I managed to fit an extra attribute mode into VideoNuLA that can mimic the Spectrum's display. Over Christmas I started to write an emulator for the Pi co-pro...
by RobC
Sun Jan 07, 2018 3:16 pm
Forum: hardware
Topic: A3020 Restoration
Replies: 14
Views: 318

Re: A3020 Restoration

IIRC, from the A3020 i repaired a few years ago, the RTC/CMOS chip is further away from the battery in the A3020 so this might not be such a problem. However, it's the HDD/floppy interface 82C711 and multiple associated tracks which are first in line for damage on this one :( Ah, true Steve - I'd f...
by RobC
Sat Jan 06, 2018 5:01 pm
Forum: hardware
Topic: A3020 Restoration
Replies: 14
Views: 318

Re: A3020 Restoration

What is the recommended mod to add a battery again? And will they boot without a battery? A working machine should boot without a battery but will probably need its CMOS RAM settings to be reset. See here for how to reset them (you hold down the required key on power-up): http://www.riscos.com/supp...
by RobC
Fri Jan 05, 2018 10:33 pm
Forum: hardware
Topic: A3020 Restoration
Replies: 14
Views: 318

Re: A3020 Restoration

JannievanZyl wrote:Or don't they need drives to boot?

They boot from ROM so don't need a hard drive (but a hard drive is a very useful addition).

The corrosion can damage PCB tracks and my experience is that the connections to the floppy, hard drive and parallel port can be badly affected on the A3020.
by RobC
Fri Dec 29, 2017 3:16 pm
Forum: hardware
Topic: Acorn Ethernet 3 podule EPROM and RISCiX
Replies: 8
Views: 327

Re: Acorn Ethernet 3 podule EPROM and RISCiX

Here's the ROM image from my Ethernet III podule. The EPROM was an ST M27C1001.

It's dated from 1992 so I guess there's a good chance it'll work with RO2 as I'm pretty sure I got hold of my first RO3 ROMs in late 92...
by RobC
Thu Dec 28, 2017 5:23 pm
Forum: hardware
Topic: Acorn Ethernet 3 podule EPROM and RISCiX
Replies: 8
Views: 327

Re: Acorn Ethernet 3 podule EPROM and RISCiX

I don't believe RISCiX worked (at least, not without some tweaks by Brian Brunswick that I'm not sure ever saw the light of day) with any Ethernet podules other than EtherH and EtherB. And those didn't need a ROM in for RISCiX to recognise them and work with them. I have one of these in my R260 and...

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