Search found 336 matches

by cmorley
Sat Feb 17, 2018 6:04 pm
Forum: other vintage computer hardware, software and games
Topic: Finding a short circuit
Replies: 5
Views: 129

Re: Finding a short circuit

Freeze spray (or upside down air duster) is an option. Where the frost melts quickly there is lots of heat being dissipated. Cheaper than freeze spray is 99% IPA (isopropanol). Spray/pour it on... where it drys out quickly hints at where the short is.
by cmorley
Sat Feb 10, 2018 7:39 pm
Forum: hardware
Topic: Screen shadow memory
Replies: 18
Views: 516

Re: Screen shadow memory

The watford 32K shadow board 12K overlaps &8000+. They seem to be fairly unloved and I've seen a few go on ebay for as little as £5-10. I've got one.
by cmorley
Sat Feb 10, 2018 7:26 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

I hooked up a PLD and now I've got the bidirectional coms working. So far so good. I've made it play nice with a copro so you can daisy chain any external copro through it. Address Write Read ====================================== FEF0-FEF8 copro copro FEF9-FEFE USB FIFO USB FIFO FEFF tube on/off FT...
by cmorley
Sat Feb 10, 2018 10:38 am
Forum: hardware
Topic: BBC Master noob
Replies: 48
Views: 1112

Re: BBC Master noob

New to the Master as well I've been following this thread and others about CMOS batteries, *CONFIGURE etc. I saw Daniel's comment about NiMH and did a bit of investigating. It seems that Issue 2 motherbaords have Q4 a p channel jfet connected between the battery connector and ground. The gate is con...
by cmorley
Fri Feb 09, 2018 3:29 pm
Forum: hardware
Topic: BBC Master noob
Replies: 48
Views: 1112

Re: BBC Master noob

Looks like there is probably a diode case and a resistor in there...
by cmorley
Fri Feb 09, 2018 9:01 am
Forum: for sale / freebies
Topic: Print master ROM boxed
Replies: 0
Views: 60

Print master ROM boxed

Anyone give me a tenner + postage for a boxed tested Print master ROM & manual?

Photo0739.jpg
by cmorley
Thu Feb 08, 2018 8:56 pm
Forum: other vintage computer hardware, software and games
Topic: Apple II Super Serial Card Rebuild
Replies: 19
Views: 407

Re: Schematic notation...

Jumpers? Normally connected & normally open.
by cmorley
Thu Feb 08, 2018 7:58 am
Forum: hardware
Topic: OS RAM module
Replies: 84
Views: 4948

Re: OS RAM module

For the BCPL you can execute from either OS RAM bank. You'd evict the OS ROM though so to make OS calls you'd have to switch the ROM back, call, switch to RAM, resume. Keeping the OS ISRs running isn't too hard. You could either copy them to OS RAM or switch to ROM and back every interrupt (with the...
by cmorley
Wed Feb 07, 2018 8:26 pm
Forum: hardware
Topic: OS RAM module
Replies: 84
Views: 4948

Re: OS RAM module

Yes or load a patched OS. If new code is needed and more than just changing some constants for start & end of workspace then dumping some rarer used code (e.g. CFS) and trampolining to it in the physical OS ROM would work. More code space & all functionality. The OS RAM would need to be conf...
by cmorley
Wed Feb 07, 2018 8:29 am
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

Quantity guestimate... board (B), pld (P) : ⋅ sweh (USA) 1xB 1xP ⋅ hoglet 1xB 1xP ⋅ RobC 1xB 1xP ⋅ Coeus 1xB 1xP PM me and I'll add you to the list. If there are several people in one country who want one then it might make more sense for one of them to order ...
by cmorley
Tue Feb 06, 2018 12:50 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

Photos of the prototype I made up. Not many wires needed as you can see! I cut the track on the purple board to the LED TX/RX LED (for RS232 mode) which shares the pin with ~WE (FIFO CPU mode). I did this so the NOT gate which drives the clock in the beeb is not sinking the LED current - LED is conn...
by cmorley
Mon Feb 05, 2018 3:34 pm
Forum: general
Topic: Today I received.....
Replies: 4431
Views: 274542

Re: Today I received.....

Had this a few weeks but I recapped it because some were leaking. Thanks Commodore for putting a cap between the keyboard flexi connector and audio phono. Photo1190.jpg Today... my first one :) Photo1191.jpg It works... imagine my surprise. Photo1192.jpg More surprise. Photo1193.jpg So a battery pac...
by cmorley
Mon Feb 05, 2018 2:02 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

Yeah I hit the VCP (virtual com port) throughput limit on this laptop.

I tried a quick C# bulk read into buffer and it drops packets while flat out on one core.

So I tried a quick d2xx bulk reader in C# and it drops nothing using <5% CPU in debug mode.
by cmorley
Sun Feb 04, 2018 6:42 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

This laptop is quite old with a Core 2 Duo T9300... pedestrian by modern standards. Tweaking settings reduces the dropped frames so it is the laptop not the FT232H. Hence why I think the D2xx FTDI drivers will fix it even on this slow beast. I used a counter (actually @ &7c00 so I can see it on ...
by cmorley
Sun Feb 04, 2018 4:58 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

When capturing from the FX2 with fx2pipe, there seems to be a similar "discontinuity" about 4KB in. The only way to avoid this seems to be to power cycle the board. Rather than do this each time, I've taken to using dd to drop the first 8KB of any capture, and the remainder is always clea...
by cmorley
Sun Feb 04, 2018 2:46 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

I knocked up an adapter on veroboard to get rid of the rats nest of jumpers. It isn't sending wrong bytes, the PC is missing blocks of bytes. I've been using type comn: > log.bin from a windows command prompt and cat /dev/ttySn > log.bin from cygwin both with the same effect so I think I might have ...
by cmorley
Sat Feb 03, 2018 8:55 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

I hooked up the "CJMCU-232H" purple board to the B this evening and it logs. I'm now using hoglet's latest code from github to decode. I'm getting a few corrupt bytes but I think this is poor signal integrity because I just shoved some jumper wires into an IDE cable to give this purple boa...
by cmorley
Sat Feb 03, 2018 4:41 pm
Forum: hardware
Topic: R65C02 in a Beeb
Replies: 51
Views: 1160

Re: R65C02 in a Beeb

The problem is likely that all the 6502 timing for NMOS or CMOS is relative to phi2. Acorn used phi1 as the main computer clock source... phi1 doesn't have identical relationship to phi0 (or phi2) between NMOS & CMOS. phi1 rising lags the phi2 falling edge on NMOS. It can lag or lead on a Rockwe...
by cmorley
Fri Feb 02, 2018 10:39 am
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

One of the cheap boards arrived today. Quality looks fine. The FTDI drivers detected it and installed it so it seems OK. I haven't hooked it up yet. https://www.ebay.co.uk/itm/FT232H-high-speed-Multifunction-USB-to-JTAG-UART-FIFO-SPI-I2C-module-UK/253164096349?ssPageName=STRK%3AMEBIDX%3AIT&_trks...
by cmorley
Fri Feb 02, 2018 10:02 am
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

Chris, FT232H or FT2232H boards are available on eBay for £6-7 delivered. Could you post a link to the kind of board you are using? I've been using an official FTDI board so far which is £15+VAT IIRC from Mouser. The cheap boards from China haven't arrived yet. I'll post the links once I've checked...
by cmorley
Fri Feb 02, 2018 10:00 am
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

Cold boot works fine. It synchronises on the reset vector pull and the OS sets everything from there. The boot.bin in the logs rar file I uploaded is a cold boot log. It should be very good for helping diagnose long beep problems.
by cmorley
Sun Jan 28, 2018 8:57 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 30
Views: 890

Re: Minimal Tube 6502decode bus snoop with FTDI USB

Hi Dave, Good work. No I hadn't looked anything further since my 'seems to work' post. I was waiting for the cheap FT232H boards to arrive on the slow boat from China before doing anything more. I fixed up a few things with the new accumulator which I saw were obvously wrong - I assume you saw them ...
by cmorley
Sun Jan 28, 2018 1:57 pm
Forum: hardware
Topic: BBC Model B and DFS Problem
Replies: 75
Views: 1596

Re: BBC Model B and DFS Problem

And there ist a physical problem, all rom sockets a full, is there an extended socket for the ram needed? I make some upgrades for Bs which free up sockets. RAM with a ROM socket on the top & EEPROM which allows 4 ROM images in one socket. Both help free up sockets. http://stardot.org.uk/forums...
by cmorley
Sat Jan 27, 2018 9:01 pm
Forum: hardware
Topic: BBC Model B and DFS Problem
Replies: 75
Views: 1596

Re: BBC Model B and DFS Problem

I checked the clock on Pin 3 of the 8271: none. On Pin 4 IC86 (74LS393) no clock, too. But at the input of IC86 Pin 1 there ist the 8 MHz clock. IC86 was bad. I exchanged it and the beeb starts normal now with DFS message. Now I will put the Floppydrive at the computer. Which commands can I try to ...
by cmorley
Sat Jan 27, 2018 10:12 am
Forum: hardware
Topic: BBC Model B and DFS Problem
Replies: 75
Views: 1596

Re: BBC Model B and DFS Problem

Oh and Ralf, check 8271 pin 4 the reset pin too. I forgot to write that... it should be LOW (high indicates reset).
by cmorley
Sat Jan 27, 2018 10:06 am
Forum: hardware
Topic: M512 1MB Expansion...
Replies: 7
Views: 383

Re: M512 1MB Expansion...

You want to put 4 four bit DRAMs in place of 16 one bit DRAMs? The address space is the same size so you should be able to just do it. Swapping DRAM for static RAM is more problematic because you need to add latches and RAS CAS decode logic to turn the DRAM time mulitiplexed address back into an SRA...
by cmorley
Sat Jan 27, 2018 7:23 am
Forum: hardware
Topic: BBC Model B and DFS Problem
Replies: 75
Views: 1596

Re: BBC Model B and DFS Problem

Is the clock (pin 3) to the 8271 OK? It is generated by IC86 pin 4 74LS393 dual 4-bit ripple counter & the source is 8Mhz from link S27 south.
by cmorley
Thu Jan 25, 2018 12:25 pm
Forum: hardware
Topic: Question about B and Master
Replies: 18
Views: 510

Re: Question about B and Master

Firetrack, The Hobbit

Applications:
Quest Paint
by cmorley
Tue Jan 23, 2018 12:42 pm
Forum: hardware
Topic: Connecting SEGA Mega Drive controllers to the beeb
Replies: 27
Views: 756

Re: Connecting SEGA Mega Drive controllers to the beeb

tricky wrote:Thanks guys, I might try and do one that I actually get produced.

PCBs from China are so cheap there is almost no risk - apart from wasted time. e.g. 5 PCBs from Elecrow will cost you $5 + $5 P&P! Worth a shot.
by cmorley
Tue Jan 23, 2018 11:14 am
Forum: hardware
Topic: Connecting SEGA Mega Drive controllers to the beeb
Replies: 27
Views: 756

Re: Connecting SEGA Mega Drive controllers to the beeb

For this board, I would not worry too much about a ground pour/ground plane. Electrically irrelevant for this project but it makes routing easier because you don't need to lay traces for power and ground. Just do signals, pour and move signals or stitch with traces and vias so all power nets are co...