Search found 141 matches

by SteveBagley
Thu Feb 08, 2018 2:23 pm
Forum: off-topic
Topic: Why did CISC prevail?
Replies: 17
Views: 377

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: 17
Views: 377

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: 17
Views: 377

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: 347

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: 1161

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: 43835

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: 712

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: 489

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: 402

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: 402

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: 253

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: 402

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: 509

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...
by SteveBagley
Wed Oct 18, 2017 9:22 am
Forum: hardware
Topic: 10base-2 crossover?
Replies: 35
Views: 1826

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: 4431
Views: 274600

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: 1020

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: 17641

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: 815

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: 2442

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...
by SteveBagley
Tue Aug 08, 2017 10:19 pm
Forum: hardware
Topic: 68B54 emulation = wifi enabled Master
Replies: 23
Views: 1272

Re: 68B54 emulation = wifi enabled Master

One option that might help, given that ANFS isn't standard on any Beeb (save the MasterET) is to also alter ANFS as well to make it work better with the ESP8266. There's lots of things ANFS has to deal with that cannot happen when it is interfacing with the ESP8266 (e.g. line busy, network collision...
by SteveBagley
Thu Aug 03, 2017 7:40 pm
Forum: hardware
Topic: Domesday86 Project
Replies: 82
Views: 4596

Re: Domesday86 Project

(As a side note - I wonder if the original 1" tape used to master the discs was transferred in the BBC's archive project. That would be on both Digtal Betacam and uncompressed SD 601 on LTO tape - in component 4:2:2 format decoded via a BBC TRANSFORM PAL decoder - the highest quality PAL decod...
by SteveBagley
Tue Aug 01, 2017 9:51 pm
Forum: hardware
Topic: BBC A3000 + Watford Electronics ARM3 - installation woes
Replies: 24
Views: 1062

Re: BBC A3000 + Watford Electronics ARM3 - installation woes

Just a thought but did the A3000 ever ship with MEMC1 (or has one been used to repair it)? That wasn't compatible with the ARM3 iirc.

Steve
by SteveBagley
Mon Jul 31, 2017 4:30 am
Forum: introduce yourself
Topic: Hello everyone
Replies: 10
Views: 807

Re: Hello everyone

Serial would work, it's what I did before, but as the HD doesn't work I can't load up the terminal program I used to send the files like I did before! I suppose I could always code up something very simple from scratch to receive serial bytes and write them to a file, at least to get some kind of p...
by SteveBagley
Wed Jul 19, 2017 9:42 pm
Forum: other vintage computer hardware, software and games
Topic: Show us your retro computers
Replies: 71
Views: 5017

Re: Show us your retro computers

This report and pictures, written by one of our PhD students, about our display of old computers at our graduation yesterday might amuse people -- particular the bit about the Beeb releasing Magic Smoke in the middle! http://aaronsplace.co.uk/blog/2017-07-18-university-of-nottingham-computer-science...
by SteveBagley
Mon Jul 17, 2017 12:42 am
Forum: general
Topic: Archimedes 30th birthday?
Replies: 12
Views: 1023

Re: Archimedes 30th birthday?

Thanks for the tip-off -- hope we did it justice!

https://www.youtube.com/watch?v=rh7kpkwXnwA

Steve
by SteveBagley
Sat Jun 03, 2017 3:18 pm
Forum: off-topic
Topic: x86 Internals for Fun & Profit
Replies: 12
Views: 1206

Re: x86 Internals for Fun & Profit

I wonder if Intel wouldn't be better off just dumping the baggage and exposing whatever RISC core they use inside the x86 processors. Maybe as the conventional computing world moves towards ARM they'll have to do something like that to stay relevant. ARM CPUs are just as complex inside these days -...
by SteveBagley
Fri Jun 02, 2017 10:56 am
Forum: hardware
Topic: 80 column teletext
Replies: 24
Views: 2253

Re: 80 column teletext

Sinclair found that often you can reduce the refresh frequency to lower than the manufacturers stated frequency, and the DRAM chips will still retain their contents. Of course, there are limits to how long you can go between refreshing before intermittent memory corruption occurs... A friend of min...
by SteveBagley
Fri Jun 02, 2017 10:23 am
Forum: hardware
Topic: Upgrades to make Master out of an Electron?
Replies: 14
Views: 1090

Re: Upgrades to make Master out of an Electron?

Thinking through my shadow RAM idea some more, it might just work. With ~40k 2MHz clock cycles per frame, the 6502 would have to be to be working pretty hard to write more than 9728 bytes per frame. If the CPLD used part of the attached SRAM to keep a ring buffer of addresses that had been written ...
by SteveBagley
Wed May 31, 2017 1:43 pm
Forum: programming
Topic: 6502 BASIC Compiler
Replies: 25
Views: 1906

Re: 6502 BASIC Compiler

If you wrote a threaded code compiler (as, if I remember correct, at least one of the BASIC compilers did on the Arc) Was there more than 1 Arc Compiler? I only found details about the ABC one, which was written by Paul Fellows and later owned by Oak and then Castle. Was there more? I had a hooky c...
by SteveBagley
Wed May 31, 2017 10:20 am
Forum: programming
Topic: 6502 BASIC Compiler
Replies: 25
Views: 1906

Re: 6502 BASIC Compiler

BASIC on the Acorn 8 bit computers essentially runs on a virtual machine (abstracted 32bit integers and 5 byte floating point IIRC). VMs have a major advantage of reducing code size at the expense of speed. Good examples are Steve Woz's Sweet 16 and the Zork VM (many online references for both of t...