Search found 152 matches

by SteveBagley
Sat May 26, 2018 9:09 am
Forum: stardot.org.uk
Topic: Image sizes
Replies: 59
Views: 713

Re: Image sizes

I’d say 1024x1024 is rather low these days given the trend toward HiDPI screens— it won’t display full screen on many phones, and would require scaling up to fill more than half a hidpi laptop screen, or a quarter of 4K monitor without requiring scaling up. Now scaling's not a problem for a Beeb or ...
by SteveBagley
Thu May 24, 2018 2:41 pm
Forum: general
Topic: Remarkable videos recently posted on Youtube
Replies: 157
Views: 16094

Re: Remarkable videos recently posted on Youtube

https://www.youtube.com/watch?v=vskNak4TeRs Computerphile (a regular series on comp sci topics), just posted a video on software preservation. The example used was a bit of beeb educational software going via an A3000 to BeebEm on Mac. Ahem, it's an A310 :) There's a companion piece on the actual B...
by SteveBagley
Wed Apr 11, 2018 10:02 am
Forum: other vintage computer hardware, software and games
Topic: C64 fault
Replies: 7
Views: 482

Re: C64 fault

crj wrote:(Plus, blown PSU capacitors don't have a characteristic effect on the video display.)
Maybe we need an olfactory Beeb repair guide? :)

Steve
by SteveBagley
Sun Apr 08, 2018 7:55 am
Forum: hardware
Topic: Reverse Tube - an amusing idea
Replies: 8
Views: 577

Re: Reverse Tube - an amusing idea

The motivating example was to do most stuff on machine A, but have it use the filing systems from machine B so it can keep PAGE at &E00. Ah, I see -- basically HostFS, except using the actual Tube protocol! (HostFS uses a modified version of the protocol so it can run over a serial port.) Acorn had...
by SteveBagley
Tue Mar 27, 2018 6:32 pm
Forum: hardware
Topic: A5000 woes
Replies: 18
Views: 837

Re: A5000 woes

Have you tried pressing RESET? Mine, oddly, will sometimes only boot if RESET is pushed…

Steve
by SteveBagley
Sat Mar 17, 2018 8:29 am
Forum: hardware
Topic: I've wondered this for thirty years...
Replies: 19
Views: 973

Re: I've wondered this for thirty years...

I speculated a few weeks ago that the B+128K was a reaction and spoiler to Sinclair's release of the Spectrum 128K in Spain and its impending release in the UK. The dates fit for it being a motivator.

Steve
by SteveBagley
Fri Mar 16, 2018 11:53 am
Forum: hardware
Topic: Myelin's in-system updateable MegaROM for the BBC Master 128
Replies: 31
Views: 1600

Re: Myelin's in-system updateable MegaROM for the BBC Master 128

myelin wrote:Exactly. So I need a way to get the CPU to issue continuous reads from memory-mapped I/O locations or paged ROMs that aren't present :) The latter is easier, because my board acts as a paged ROM.
How about loading a branch instruction into the VIAs registers and jumping to it?

Steve
by SteveBagley
Mon Mar 05, 2018 11:20 pm
Forum: hardware
Topic: Acorn's Second Processors and the Tube - what, and why
Replies: 47
Views: 3084

Re: Acorn's Second Processors and the Tube - what, and why

In terms of how the software works, you need to think about the two processors as effectively being independent systems -- except they can send messages to each other (conceptually this would be the same as if two processors linked via serial, or even a TCP/IP socket) via the TUBE ULA. This appears ...
by SteveBagley
Sun Mar 04, 2018 10:07 am
Forum: acorn atom
Topic: Crazy idea? Downgrade Electron to an Atom? Possible?
Replies: 19
Views: 867

Re: Crazy idea? Downgrade Electron to an Atom? Possible?

paulb wrote:", and actually used some kind of bizarre networking arrangement that had an Apple 2 as the fileserver, at least for the ones that were networked.
Probably best to move this into a different thread but do yo you have any more details about how this was setup?

Steve
by SteveBagley
Mon Feb 19, 2018 5:10 pm
Forum: software: other
Topic: Hacking the school Econet
Replies: 15
Views: 1004

Re: Hacking the school Econet

I never had any direct experience with Econet, but I seem to remember that there were those remote procedure calls that acted like a huge backdoor, allowing remote users to call MOS routines. I guess that people might have used those to exploit the weaknesses and gain privileges. Not to gain privil...
by SteveBagley
Mon Feb 19, 2018 12:13 am
Forum: hardware
Topic: B+64K - 12k sideways ram working
Replies: 15
Views: 743

Re: B+64K - 12k sideways ram working

So it is interestingly that Acorn had a change of heart with the B+128K, though the extra RAM board shoe horned in suggests it was a bit of a last-minute thing. I wonder if the September 1985 Spectrum 128 announcement might have had something to do with the BBC B+ 128's creation? Personally, the B+...
by SteveBagley
Thu Feb 08, 2018 2:23 pm
Forum: off-topic
Topic: Why did CISC prevail?
Replies: 21
Views: 1002

Re: Why did CISC prevail?

I suppose the challenge for ARM is how to maintain its edge in terms of power efficiency, which is presumably why it has captured most of the 'mobile' market, whilst introducing such 'CISC-like' complexities into the CPU. I think it is as much a case of making design assumptions that are relevant f...
by SteveBagley
Thu Feb 08, 2018 11:21 am
Forum: off-topic
Topic: Why did CISC prevail?
Replies: 21
Views: 1002

Re: Why did CISC prevail?

Something else I find interesting is that the 64-bit ARM architecture has ditched one of the key features of the original 32-bit instruction set: that every instruction can be conditional. There are just a few conditional instructions left in the 64-bit set, such as conditional jumps. This is much ...
by SteveBagley
Thu Feb 08, 2018 8:51 am
Forum: off-topic
Topic: Why did CISC prevail?
Replies: 21
Views: 1002

Re: Why did CISC prevail?

So I don't think CISC prevailed. I think CISC became more RISC-like and RISC became more CISC-like. Right now, ARM and x86, the world's two dominant CPU architectures, are way more similar than they were in 1988. Absolutely, my understanding is that modern ARM CPUs have microcode and crack instruct...
by SteveBagley
Tue Feb 06, 2018 12:28 pm
Forum: hardware
Topic: Thought experiment: Iomega zip drive for the BBC
Replies: 10
Views: 553

Re: Thought experiment: Iomega zip drive for the BBC

How standard is the SCSI? I'm wondering if you could wire it up on the 1MHz bus so that ADFS sees it as a normal SCSI hard disc?

Steve
by SteveBagley
Sun Feb 04, 2018 1:30 pm
Forum: hardware
Topic: R65C02 in a Beeb
Replies: 51
Views: 1838

Re: R65C02 in a Beeb

Wasn't there a thread a few days back where it was mentioned that the memory address multiplexers were critical in the sense that, while officially available from more than one supplier, in practice only one supplier's part actually worked? Or am I mis-remembering. Furber directly describes this pr...
by SteveBagley
Mon Jan 15, 2018 5:46 pm
Forum: community projects
Topic: How many sold? German tank problem:serial nums wtd
Replies: 289
Views: 46252

Re: How many sold? German tank problem:serial nums wtd

Was reading this PDF and it suggests that the number off A440 (not A440/1) produced might be significantly higher than the calculations in the first post suggest… http://chrisacorns.computinghistory.org.uk/docs/Acorn/CSN/Acorn_CSNews2.pdf It lists the range of serial numbers that need certain field ...
by SteveBagley
Sat Jan 06, 2018 12:07 am
Forum: off-topic
Topic: CPU International Crisis - Are We All Doomed?
Replies: 18
Views: 1095

Re: CPU International Crisis - Are We All Doomed?

[*]Not including a timer that has sufficient resolution to be useful for this kind of measurement[/list] or some combination of the two. That's not possible -- I think people demoed Spectre attacks using javasciprt in another thread that just decremented a counter to time the fetches from the cache...
by SteveBagley
Thu Jan 04, 2018 9:35 pm
Forum: hardware
Topic: Acorn M4
Replies: 7
Views: 704

Re: Acorn M4

Just been looking at the photo of the motherboard above and noticed it has a Z8530 SCC chip on it? Is this the only Acorn machine to use the SCC? If so, does anyone know why they would have chosen (and presumably written drivers for) this over the chip used in the Arc? I wonder if they were consider...
by SteveBagley
Fri Dec 29, 2017 7:41 pm
Forum: hardware
Topic: Acorn Ethernet 3 podule EPROM and RISCiX
Replies: 8
Views: 593

Re: Acorn Ethernet 3 podule EPROM and RISCiX

RobC wrote: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...
Many thanks, I’ll give it a whirl and see what happens…

Steve
by SteveBagley
Thu Dec 28, 2017 5:56 pm
Forum: hardware
Topic: Acorn Ethernet 3 podule EPROM and RISCiX
Replies: 8
Views: 593

Re: Acorn Ethernet 3 podule EPROM and RISCiX

I have one of these in my R260 and it's definitely recognised by RISCiX: http://chrisacorns.computinghistory.org.uk/32bit_UpgradesA2G/Acorn_AEH54_Ethernet.html That’s good to hear… I think the problem I’m having is the memory crash leaving the podule paving register in a state so that RISCiX just d...
by SteveBagley
Thu Dec 28, 2017 1:19 pm
Forum: emulators
Topic: Model B+ Disc Interface
Replies: 8
Views: 465

Re: Model B+ Disc Interface

Doesn’t the B+ motherboard support both the 8271 and the 1770? Also, I think the B+ motherboard was used in a few other places without either (Acorn X.25 gateway?)…

Steve
by SteveBagley
Thu Dec 28, 2017 1:11 pm
Forum: hardware
Topic: Acorn Ethernet 3 podule EPROM and RISCiX
Replies: 8
Views: 593

Acorn Ethernet 3 podule EPROM and RISCiX

Does anyone know what type of EPROM was used in the Acorn/Atomwide Ethernet III podule? I have one I’m trying to get working under RISCiX (on a heavily expanded A305 no less! :-)) but unfortunately the on-board EPROM is from 1998 and so crashes RISC OS 2 at boot when the modules (MBufManager I think...
by SteveBagley
Sun Nov 12, 2017 2:08 pm
Forum: hardware
Topic: Trojan Room Coffee Pot
Replies: 8
Views: 662

Re: Trojan Room Coffee Pot

I was looking at the video digitiser colour adapter... It kind of looks like the other Wild Vision cards (unsurprisingly) but it's the only one I've seen that has a video out and I wasn't prepared to buy it based on a "might work" when I know that the WE digitiser will work as long as the hardware ...
by SteveBagley
Wed Oct 18, 2017 9:22 am
Forum: hardware
Topic: 10base-2 crossover?
Replies: 77
Views: 3671

Re: 10base-2 crossover?

That would turn it into a non-standard A3010 - but yes, that's the route to getting both going on an A3010 :D However, that mod's not for the faint hearted. Could you not modify the podule ROM to contain enough modules to TFTP boot the rest of the network modules needed to netboot the A3010 (i.e. a...
by SteveBagley
Sun Oct 15, 2017 7:55 pm
Forum: general
Topic: Today I received.....
Replies: 4634
Views: 311950

Re: Today I received.....

Over the past week really…

An Acorn AKA31 SCSI Podule off eBay and from CJE, an AEH54 Ethernet Podule and MEMC1A chip. Hopefully, this will let me get to the point being able to run RISC iX on one of my Archimedes.

Steve
by SteveBagley
Sun Oct 15, 2017 11:42 am
Forum: software: other
Topic: BBC Domesday Project - Source code available
Replies: 13
Views: 1272

Re: BBC Domesday Project - Source code available

There are two possibilities really (and only more close examination of the code will tell)... 1) it was all developed on Masters and the code on the A500 is more related to Domesday Display and the other projects that came after or 2) Early A500s were used in the later stages of the project to spee...
by SteveBagley
Sun Oct 08, 2017 1:11 pm
Forum: software
Topic: RISC iX - Cloned!
Replies: 168
Views: 19620

Re: RISC iX - Cloned!

This seems to be the best place to ask about RISX iX — there'll probably be a few more questions coming as I intend to upgrade one of my Arcs and install it for a play (I wonder if it’ll be the first A305 upgraded to be able to run Risc iX ;-)) But, I was reading about the Acorn R225 diskless Unix w...
by SteveBagley
Sat Sep 30, 2017 1:13 pm
Forum: software
Topic: ST-506 Hard disc image creation
Replies: 17
Views: 1094

Re: ST-506 Hard disc image creation

I was trying to avoid having to write anything, I was looking for something that would just work. I don't have any other ADFS hard disc to try it on, and I don't want to be using the old drive any longer than necessary. I came across this a couple of years ago -- looks like the programming has alre...
by SteveBagley
Tue Sep 12, 2017 7:01 am
Forum: hardware
Topic: Resurrecting A5000
Replies: 41
Views: 2907

Re: Resurrecting A5000

With my A5000 temporarily (I hope) dead, I've got the drives in an A4000. I've been using it to back up the server. Yea gods, the A4000 is slow. I take it the A4000 is the Acorn Electron of the RISC OS world. A compatible machine but with all the memory access crippled. The main difference is CPU s...