Search found 5960 matches

by 1024MAK
Sun Apr 23, 2017 4:49 pm
Forum: hardware
Topic: Adding SWRAM to BBC
Replies: 6
Views: 106

Re: Adding SWRAM to BBC

It's probably the address decoding and bank decoding logic that is causing you grief.

Mark
by 1024MAK
Sun Apr 23, 2017 2:01 pm
Forum: hardware
Topic: Adding SWRAM to BBC
Replies: 6
Views: 106

Re: Adding SWRAM to BBC

The socket for ROM number 15 has been split into two 8K sockets -15a and 15b- to allow use of 8K byte CMOS RAM chips and therefore provides support for up to 16K of SIDEWAYS RAM. The logic is arranged such that any write performed to the SIDEWAYS ROM area of the machine will access the RAM directly...
by 1024MAK
Sun Apr 23, 2017 9:12 am
Forum: general
Topic: thebbclives website gone.
Replies: 25
Views: 733

Re: thebbclives website gone.

Arcadian wrote:
GordonSJ wrote:P.S. good to hear that Stairway to hell is not going anywhere any time soon.

Also, I've just this second renewed the stairwaytohell.com domain for a further nine years, so hopefully that gives you some more assurance too! :)

=D> =D> =D>

Mark
by 1024MAK
Sat Apr 22, 2017 7:26 pm
Forum: hardware
Topic: external PSU for the Beeb
Replies: 10
Views: 161

Re: external PSU for the Beeb

In general, I agree, if there are no safety problems for most things, yes try them. That's exactly what I used to do with Beebs. But after having to take a lot longer clearing up the goo that a failed X2 suppression capacitor made in one of my Beebs, I now group Beeb PSU into the check before power-...
by 1024MAK
Sat Apr 22, 2017 7:15 pm
Forum: hardware
Topic: BBC to VGA connector
Replies: 20
Views: 395

Re: BBC to VGA connector

The usefulness of trying to use a HD floppy in a DD disk drive is debatable. It works fine for some people, completely fails for others and for the remainder, it works at first, but the disk "becomes corrupted" within days or weeks later... Your best chance of success is to use HD disks th...
by 1024MAK
Sat Apr 22, 2017 2:00 pm
Forum: hardware
Topic: CMOS Battery Replacement Questions
Replies: 8
Views: 263

Re: CMOS Battery Replacement Questions

1. After the first time cleaning with vinegar, I waited a few minutes and then poured the solution of 50% water, 50% alcohol onto the affected part of the board. After 24 hours there seemed to be white fuzzy bits on the board and between some of the chips which I gently scraped off with the blunt e...
by 1024MAK
Sat Apr 22, 2017 1:43 pm
Forum: hardware
Topic: MaxRAM - New Open Hardware BBC RAM/ROM Board
Replies: 67
Views: 1501

Re: MaxRAM - New Open Hardware BBC RAM/ROM Board

I think you just need to keep going and actually show something working. Then I think the interest will build. Keep in mind that a lot of people will only show interest if there is something to buy. Depending on their level of electronic ability (and confidence), they may be happy with just a PCB o...
by 1024MAK
Sat Apr 22, 2017 1:35 pm
Forum: hardware
Topic: MaxRAM - New Open Hardware BBC RAM/ROM Board
Replies: 67
Views: 1501

Re: MaxRAM - New Open Hardware BBC RAM/ROM Board

dp11 wrote:If i was to put this into production I'd look at pin swapping the PLD and possibly some of the address pins on the Ram .

With Static RAM (SRAM), you can freely change any address line/pin for any other address line/pin, same for data lines/pins. It does make routing a bit easier :wink:

Mark
by 1024MAK
Sat Apr 22, 2017 12:50 pm
Forum: general
Topic: "Outline specification for the BBC MICROCOMPUTER system"
Replies: 177
Views: 4524

Re: "Outline specification for the BBC MICROCOMPUTER system"

Do you remember the half pence?

And the other fractions were sometimes in in recipe pages.

Mark
by 1024MAK
Sat Apr 22, 2017 1:36 am
Forum: general
Topic: "Outline specification for the BBC MICROCOMPUTER system"
Replies: 177
Views: 4524

Re: "Outline specification for the BBC MICROCOMPUTER system"

You have to keep in mind that there was NO FULLY STANDARD character set at the time. Yes ASCII was used by some computers, but not by all (ZX80, ZX81, various Commodore computers all used different character sets - PETSCII ). The teletext character set was designed for use with teletext TV transmiss...
by 1024MAK
Sat Apr 22, 2017 1:05 am
Forum: hardware
Topic: external PSU for the Beeb
Replies: 10
Views: 161

Re: external PSU for the Beeb

I'd risk turning it on. Of the 5 I have I've had two do the magical smoke trick but continued working (I didn't bother turning off just opened a window) the rest, 1 needed a startup cap change but that did no damage. I'm of the if it ain't broke school A PSU that smokes due to C1 or C2 failing IS b...
by 1024MAK
Sat Apr 22, 2017 1:00 am
Forum: hardware
Topic: external PSU for the Beeb
Replies: 10
Views: 161

Re: external PSU for the Beeb

How difficult would it be to remove the internal power supply, and modify the Beeb to use a generic laptop power supply unit? Modern laptop power supply units typically output 17V to 25V DC. Some also have a sense / control system so they can detect if they are plugged into a computer. The Beeb mai...
by 1024MAK
Fri Apr 21, 2017 12:45 pm
Forum: general
Topic: "Outline specification for the BBC MICROCOMPUTER system"
Replies: 177
Views: 4524

Re: "Outline specification for the BBC MICROCOMPUTER system"

And of course it should be said that apparently both the 6502 and the Z80 primary markets were expected to be embedded systems and such like rather than as general purpose CPUs for computers.

Mark
by 1024MAK
Thu Apr 20, 2017 9:47 pm
Forum: hardware
Topic: EEPROM for BBC micro
Replies: 24
Views: 344

Re: EEPROM for BBC micro

Did all of the following: - if I mount an EPROM or PROM (with the same rom content) in the viglen: everything works fine (proves that cable is ok) What type (NMOS or CMOS) and speed rating of EPROM did you try? Hi Marc, - type is NEC D28C256CZ-20 (max 200ns) - cable is around 20cm I know that signa...
by 1024MAK
Thu Apr 20, 2017 9:14 pm
Forum: general
Topic: "Outline specification for the BBC MICROCOMPUTER system"
Replies: 177
Views: 4524

Re: "Outline specification for the BBC MICROCOMPUTER system"

CP/M stuff... Where do you get the impression that there was any kind of graphical support in CP/M? Each manufacturer supplied a bespoke version of CP/M for their hardware... Also, I read Mr Zaks z80 book (the opposite of the 6502 one I used to use) and he mentioned that the z80 loop instructions a...
by 1024MAK
Thu Apr 20, 2017 6:19 pm
Forum: hardware
Topic: EEPROM for BBC micro
Replies: 24
Views: 344

Re: EEPROM for BBC micro

Oh, and how long is the ribbon cable?

Mark
by 1024MAK
Thu Apr 20, 2017 5:57 pm
Forum: hardware
Topic: EEPROM for BBC micro
Replies: 24
Views: 344

Re: EEPROM for BBC micro

What type (NMOS or CMOS) and speed rating of EPROM did you try?

Mark
by 1024MAK
Wed Apr 19, 2017 8:03 pm
Forum: hardware
Topic: Electron unstable/fails to boot when Plus 1 is connected
Replies: 12
Views: 234

Re: Electron unstable/fails to boot when Plus 1 is connected

Dave means one of these. Image
As Dave says, great for cleaning all manner of electrical contacts. They should be available from any good electronic supplier.

Mark
by 1024MAK
Wed Apr 19, 2017 1:03 pm
Forum: hardware
Topic: Electron unstable/fails to boot when Plus 1 is connected
Replies: 12
Views: 234

Re: Electron unstable/fails to boot when Plus 1 is connected

What happens with edge-connectors that are not firmly fixed is the contacts move as a result of vibration and movement of the computer or interface. As the contacts move, sometimes one or more may momentarily experience greater contact resistance (either open circuit or just a high resistance connec...
by 1024MAK
Wed Apr 19, 2017 12:46 pm
Forum: general
Topic: thebbclives website gone.
Replies: 25
Views: 733

Re: thebbclives website gone.

Hi Guys I can assure you all that the 8BS will be around for as long as there is somewhere to put it. Sadly, at the moment, the 8BS server is down, Jess is mending it after it was hacked. She said it would take a few days, let's hope that's not much longer. Meanwhile, there is this: http://stardot....
by 1024MAK
Wed Apr 19, 2017 9:27 am
Forum: hardware
Topic: BBC to VGA connector
Replies: 20
Views: 395

Re: BBC to VGA connector

Yes, as Daniel says, the video socket you highlight with a green square is a composite video output. It outputs a 625 line 50Hz signal. If you use a Phono / RCA / Cinch to Phono / RCA / Cinch video cable and connect it to the composite video input on a TV (often a socket with yellow plastic) and sel...
by 1024MAK
Wed Apr 19, 2017 8:52 am
Forum: other vintage computer hardware, software and games
Topic: Fixing a Superbrain up
Replies: 33
Views: 469

Re: Fixing a Superbrain up

I don't think the PSU is now the cause of the trouble. I would say that the AC component (actually AC ripple) is now within acceptable levels. The adjustment of the +5V rail so that you get exactly +5.0V at the end of the 5V distribution tracks is sensible. I agree with Dave in that the area to look...
by 1024MAK
Tue Apr 18, 2017 4:34 pm
Forum: other vintage computer hardware, software and games
Topic: Fixing a Superbrain up
Replies: 33
Views: 469

Re: Fixing a Superbrain up

Hi Jon Which Z80 ICE are you using? In most designs using 4116 DRAM chips, the DRAM /RAS goes active during /REFRESH. Can you confirm this with a 'scope? Is the ROM socketed? If it is, is it a type where you can temporarily fit a EPROM with a simple test program? All the test program should do is to...
by 1024MAK
Tue Apr 18, 2017 12:30 pm
Forum: hardware
Topic: On the B+ why did Acorn 'ignore' the Aries B20/B32 patents owners?
Replies: 3
Views: 217

Re: On the B+ why did Acorn 'ignore' the Aries B20/B32 patents owners?

Click URL button. After the first URL bit add an equals symbol followed by the URL address, between the URL tags add some descriptive text. So:- link to hardware section This link looks like this: [url=http://stardot.org.uk/forums/viewforum.php?f=3]link to hardware section[/url] Or if the URL is a h...
by 1024MAK
Tue Apr 18, 2017 12:14 pm
Forum: hardware
Topic: BBC to VGA connector
Replies: 20
Views: 395

Re: BBC to VGA connector

I take it that at least one of your televisions is now working okay with your Beeb using a SCART lead? VGA is also a RGB video system (where the red video channel, the green video channel and the blue video channel are carried separately), but the frequency of the video signals and synchronisation s...
by 1024MAK
Tue Apr 18, 2017 11:08 am
Forum: hardware
Topic: BBc with memory or addressing problem HELP!
Replies: 16
Views: 303

Re: BBc with memory or addressing problem HELP!

Help with RAM faults in this thread . Piggybacking mostly only works when the pin output driver in a chip fails. It will not work if the output pin in question is working and the fault is "deeper" inside the chips circuitry. DRAM chips are complex beasts, so can fail in many ways. Well the...
by 1024MAK
Tue Apr 18, 2017 5:09 am
Forum: hardware
Topic: where to get keyboard connectors
Replies: 6
Views: 148

Re: where to get keyboard connectors

You have me wondering. I have a beeb in a Solidisk case and that came with what I think is a piece of 24-way IDC ribbon as used for the floppy interface except it has the same connector at both ends, i.e. the one that would go into the BBC disk connector rather than the edge connector on the disc d...
by 1024MAK
Tue Apr 18, 2017 4:24 am
Forum: hardware
Topic: Acorn mention 80x16(did they mean 80x12?) on 6845/SAA5050: possible on beeb?
Replies: 6
Views: 217

Re: Acorn mention 80x16(did they mean 80x12?) on 6845/SAA5050: possible on beeb?

Although the BBC B has more than 1k bytes of RAM available, in Teletext mode, because of the way the address lines are configured, the amount of RAM that can be used by the video hardware (6845) and its location within the address map is limited. See this post . So a 80 column Teletext mode is unlik...
by 1024MAK
Tue Apr 18, 2017 3:30 am
Forum: general
Topic: thebbclives website gone.
Replies: 25
Views: 733

Re: thebbclives website gone.

Ahh, found the thread :D

Chris introduces himself here.

Mark
by 1024MAK
Tue Apr 18, 2017 2:59 am
Forum: general
Topic: thebbclives website gone.
Replies: 25
Views: 733

Re: thebbclives website gone.

The admin of 8bs.com is a member here. He is called Chris.

I have had a quick look for some of his posts, but have not yet had time to finish my search.

Mark

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