Search found 579 matches

by KenLowe
Mon Apr 24, 2017 10:18 pm
Forum: hardware
Topic: Adding SWRAM to BBC
Replies: 10
Views: 1034

Re: Adding SWRAM to BBC

While recently getting my two Beebs up and running, I modified my Watford 12 ROM/RAM board to take additional 16kB SRAM chips. I don't have the board to hand, however, off the top of my head, the 74LS154N decoder has two /CE pins. One of these is connected to the output of the write-enable for the ...
by KenLowe
Mon Apr 24, 2017 8:35 pm
Forum: hardware
Topic: Adding SWRAM to BBC
Replies: 10
Views: 1034

Re: Adding SWRAM to BBC

Thanks for all the replies. I'll definitely have a look into the mod PhilC has implemented. That looks to be exactly what I need to do.
by KenLowe
Sun Apr 23, 2017 2:59 pm
Forum: hardware
Topic: Adding SWRAM to BBC
Replies: 10
Views: 1034

Re: Adding SWRAM to BBC

The type of RAM chips used back then (8k byte Static RAM - or SRAM) were relatively expensive. So they likely never considered that a user would want more than one sideways bank as RAM. The "feature" of sending writes to the allocated sideways RAM Bank was simple to do. And as said in the adverts a...
by KenLowe
Sun Apr 23, 2017 12:50 pm
Forum: hardware
Topic: Adding SWRAM to BBC
Replies: 10
Views: 1034

Re: Adding SWRAM to BBC

Interesting. Do you know if that's the same with the ATPL Sidewise ROM / RAM board? I was having similar issues adding extra memory to that board as well! All I'm trying to do is get the Level 9 graphic games running at full capacity (graphics and undo) on the BBC. I've got the Watford shadow ram bo...
by KenLowe
Sun Apr 23, 2017 11:10 am
Forum: hardware
Topic: Adding SWRAM to BBC
Replies: 10
Views: 1034

Adding SWRAM to BBC

Hi I'm having problems adding extra SWRAM to one of my BBCs. This BBC has a Watford 12 ROM / RAM board installed, and slot 14 already has 2 x 6264 memory chips giving a single 16k RAM bank at slot 14. This all works fine. I've got a couple of UM62256A-10LL memory chips (bought from ebay!) and I'm tr...
by KenLowe
Mon Apr 17, 2017 9:36 pm
Forum: hardware
Topic: BBc with memory or addressing problem HELP!
Replies: 16
Views: 1293

Re: BBc with memory or addressing problem HELP!

Firstly, try moving jumper S25 to narrow down the fault. The following gives a fairly good write up: http://mrpjevans.com/2016/01/bbc-micro-model-b-memory-repair/ Once you've narrowed the fault down to a specific chip, and assuming you've got a spare memory chip, you could the try piggy backing the ...
by KenLowe
Mon Apr 17, 2017 6:54 pm
Forum: hardware
Topic: BBC to VGA connector
Replies: 20
Views: 2043

Re: BBC to VGA connector

Could well be a region standard issue, but I thought most TVs these days were able to handle all standards. It would be worth making sure your SCART lead is wired similar to section 5.2 of this guide: http://mdfs.net/Info/Comp/BBC/Monitor/BBCtoTV.htm The important thing is that you should have the p...
by KenLowe
Mon Apr 17, 2017 6:09 pm
Forum: hardware
Topic: BBC to VGA connector
Replies: 20
Views: 2043

Re: BBC to VGA connector

I don't know why your SCART lead wouldn't work but, if you're looking to connect to a modern TV / monitor that doesn't support SCART, I suggest you go for a SCART to HDMI adaptor - connect your BBC to the adaptor using your SCART lead, then connect your TV to the adaptor using a HDMI lead. You can p...
by KenLowe
Sun Apr 16, 2017 6:46 pm
Forum: hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)
Replies: 1124
Views: 108553

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)

Right, I've run a few tests, and the results are noted below. Each test is with a clean config.txt from boa release and latest versions of bootcode.bin, fixup_cd.dat and start_cd.elf: Test 1: Add kernel=kernelrpizero.img to [pi2] & comment out kernel=kernelrpi2.img Result: Kernel not loaded. BBC doe...
by KenLowe
Sun Apr 16, 2017 9:33 am
Forum: hardware
Topic: B+64k Special 12k?
Replies: 23
Views: 3379

Re: B+64k Special 12k?

It's some time ago since I implemented the BBC+ and IntegraB memory allocation code into BeebEm, but I'm pretty sure they were the same. I wrote some notes specifically for the IntegraB and included them in the BeebEm distribution. I think this backs up the observations: There are two registers to s...
by KenLowe
Sun Apr 16, 2017 7:24 am
Forum: hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)
Replies: 1124
Views: 108553

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)

Excellent. Would you mind running a few more tests for me. I'll sort out exactly what. But I suspect it will be about 6 tests. More than happy to help, but I won't be around much today. However, I should have some time later this evening. Dominic, are you thinking there is a new property filter for...
by KenLowe
Sat Apr 15, 2017 11:12 pm
Forum: hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)
Replies: 1124
Views: 108553

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)

For pizero W testers could you try daves suggestions : - start with a blank SD card, formatted as FAT32 - Unzip the Boa release from here : - Replace the files: bootcode.bin, fixup_cd.dat and start_cd.elf with the latest versions from here Plus the attached file please rename to config.txt and put ...
by KenLowe
Thu Apr 13, 2017 10:01 pm
Forum: hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)
Replies: 1124
Views: 108553

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)

Dave,

Getting the same results as the standard BOA release. Works ok on the Zero, but doesn't work on the Zero W.
With the Zero W, the computer boots up ok, but it just doesn't recognise any Tube device.

Happy to let you borrow the Zero W for testing / developing if that would help you.
by KenLowe
Thu Apr 13, 2017 9:13 pm
Forum: hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)
Replies: 1124
Views: 108553

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)

I loaded the old release from October and that works fine. How did you get that to work on the zero w? I've just tried to copy the October release Rasp Pi Zero kernel.img file over to a newly formatted FAT32 SD card and it just causes the computer to hang on boot. I've also tried copying the cmdlin...
by KenLowe
Sun Apr 09, 2017 8:52 am
Forum: hardware
Topic: Computech Integra-B upgrade board
Replies: 13
Views: 1047

Re: Computech Integra-B upgrade board

I'll post up the image later today. Interestingly, once I've booted the disk, I can then do a reset, and a new parameter appears in the *STATUS list. This is with the standard IBOS 1.20 shipped with BeeEm. I think it's linked to the INTEGRA Windows ROM that gets loaded into one of the SWR banks when...
by KenLowe
Sat Apr 08, 2017 11:21 pm
Forum: hardware
Topic: Computech Integra-B upgrade board
Replies: 13
Views: 1047

Re: Computech Integra-B upgrade board

So, some success! The two files that are corrupt are just text files and don't actually impact the functionality... To start with, I think you might need to have multiple free SWR banks for it to work correctly. To be on the safe side, I *SRWIPEd all the SWR banks before starting. Having done that, ...
by KenLowe
Sat Apr 08, 2017 7:51 pm
Forum: hardware
Topic: Computech Integra-B upgrade board
Replies: 13
Views: 1047

Re: Computech Integra-B upgrade board

Not sure where my disk is now, or if it even works. I'll see if I can dig it out of storage, along with a FDD. I never actually had an AMX mouse, so I perhaps never got as far as I thought I had with the Windows software. The IntegraB manual indicates that there's a Windows ROM that needs to be load...
by KenLowe
Sat Apr 08, 2017 7:41 am
Forum: hardware
Topic: Computech Integra-B upgrade board
Replies: 13
Views: 1047

Re: Computech Integra-B upgrade board

I'm not sure if 1.20 was the last version, but this is the version I have. It was actually an updated version that was supplied to me by Computech after I had problems getting an older version of IBOS to correctly select DFS as the default file system when using the DNFS rom (it would always default...
by KenLowe
Fri Apr 07, 2017 8:37 pm
Forum: hardware
Topic: Computech Integra-B upgrade board
Replies: 13
Views: 1047

Re: Computech Integra-B upgrade board

My issue 3 Computech IntegraB is wired as follows: A = Green - wired to centre of S22 B = Blue - wired to centre of S20 C = Yellow - wired to SW of S21 Note that the manual indicates that A, B, C are Yellow, Blue and Green respectively for issue 1 boards. If you are getting a Language? error, then y...
by KenLowe
Wed Apr 05, 2017 9:32 pm
Forum: hardware
Topic: SOLVED - BBC Micro - IC25 cut pin
Replies: 8
Views: 1161

Re: BBC Micro - IC25 cut pin

Just a quick reply to close this one out. The data corruption issue turned out to be caused by a bad pin on the socket of IC71, causing the A7 line on the 1MHz bus port to remain high all the time. Thanks to Mark of Retroclinic for diagnosing this. I almost got there on my own. I think I belled out ...
by KenLowe
Thu Mar 23, 2017 2:23 pm
Forum: hardware
Topic: SOLVED - BBC Micro - IC25 cut pin
Replies: 8
Views: 1161

Re: BBC Micro - IC25 cut pin

I'm pretty sure the OS is the standard PB04 ROM. I'll check later, though, and confirm.

Edit: Confirming...
1. OS1.2 is the standard Acorn PB04 ROM, and
2. Links S14, S15, S16 & S17 are all closed
by KenLowe
Thu Mar 23, 2017 12:51 pm
Forum: hardware
Topic: SOLVED - BBC Micro - IC25 cut pin
Replies: 8
Views: 1161

Re: BBC Micro - IC25 cut pin

Thanks for all the feedback, guys. Taking the comments in turn: Ic 25 pin 4 cut will prevent part on the 1MHz bus working and enable you to read a secret page of memory out of the os. IIRC some machines needed a pin cut something to do with NMIs. Maybe someone got the wrong ic. That makes sense. Int...
by KenLowe
Thu Mar 23, 2017 12:49 am
Forum: hardware
Topic: SOLVED - BBC Micro - IC25 cut pin
Replies: 8
Views: 1161

SOLVED - BBC Micro - IC25 cut pin

Hi guys, Any idea why IC25 pin 4 on an issue 4 BBC might have been cut? It's a model B with Econet, 8271 DFS and speech upgrades all fitted. It's been like that for 30+ years and I've never had any problems with this computer until now.... I've just bought a new Retroclinic Datacentre and I'm having...
by KenLowe
Fri Mar 17, 2017 10:06 pm
Forum: hardware
Topic: SOLVED - System VIA Woes
Replies: 10
Views: 922

Re: SOLVED - System VIA Woes

So, I've just swapped out the 6 pin RGB socket on the motherboard for an 8 pin 'equivalent', wired the two new 'spare' pins on the 8 pin socket to the speaker plug on the motherboard, and I now have BBC audio coming through HDMI (via a RGB / SCART lead and a SCART / HDMI adaptor) to my nice new LG O...
by KenLowe
Mon Mar 13, 2017 10:25 pm
Forum: hardware
Topic: SOLVED - System VIA Woes
Replies: 10
Views: 922

Re: System VIA Woes

Thank you. :lol: :lol: :lol:

I do like a challenge. And this one has certainly been that. :? :? :?
by KenLowe
Mon Mar 13, 2017 7:40 pm
Forum: hardware
Topic: SOLVED - System VIA Woes
Replies: 10
Views: 922

Re: System VIA Woes

Okay. Think I'm sorted. Replaced IC32 this evening and the computer has been running reliably now for about 30mins. That's much longer than I was getting before. Will leave it on soak test for a couple of hours yet before i declare it a success! Edit: Success is declared! Now it's time to pimp it up...
by KenLowe
Sat Mar 11, 2017 12:24 pm
Forum: hardware
Topic: SOLVED - System VIA Woes
Replies: 10
Views: 922

Re: System VIA Woes

Yes. That's exactly the error I get. I'm almost certain the problem I have is with the addressable latch, IC32. I've been able to write a small program that just counts up a variable and prints it on the screen. Every time the number increments, I generate a beep via VDU7. After a while, the beeps w...
by KenLowe
Fri Mar 10, 2017 6:08 pm
Forum: hardware
Topic: SOLVED - System VIA Woes
Replies: 10
Views: 922

Re: System VIA Woes

Thanks for the replies, guys. I'm pretty sure the word 'searching' appears in the message. I'll get back to it later tonight and take a clear note of the wording when it happens again. It only gives this error occasionally. There are no filing system ROMS installed. I've tried a known good keyboard ...
by KenLowe
Fri Mar 10, 2017 2:18 pm
Forum: hardware
Topic: SOLVED - System VIA Woes
Replies: 10
Views: 922

SOLVED - System VIA Woes

Hi, I recently acquired an issue 7 BBC which had clearly been a repair project for the previous owner. PSU broken, keyboard broken and motherboard broken. So, with the PSU and keyboard both repaired, efforts are now focused on getting the motherboard working again. The computer will occasionally boo...
by KenLowe
Fri Feb 17, 2017 3:30 pm
Forum: hardware
Topic: Video Issue - Model B
Replies: 4
Views: 575

Re: Video Issue - Model B

Ok. Think I'm sorted . Tried a 100R resistor in the sync line (nearest one I could find to 220R!), but this didn't make any difference. ... however, having checked out the video circuit diagram I noticed that the position of S31 had an influence on the sync signal. Mine was sat at the East position....