Search found 1198 matches

by dp11
Thu Aug 20, 2020 10:42 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller craziness -- do not try this at home!

have we actually got two different controllers ? one at the top and one at the bottom ?
by dp11
Thu Aug 20, 2020 10:40 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller craziness -- do not try this at home!

I wonder if the 10 bit structure is either a timer or divider ?
by dp11
Thu Aug 20, 2020 10:26 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller craziness -- do not try this at home!

bottom left looks like 256 bytes of ROM.
by dp11
Sun Aug 16, 2020 2:11 pm
Forum: 8-bit acorn hardware
Topic: VIDPROC V2 (pin 15) - please explain!
Replies: 33
Views: 1037

Re: VIDPROC V2 (pin 15) - please explain!

Usually if the impedance is greater than the impedance if free space( 377Ohms ) Termination becomes hard .

I agree careful scoping would help.
by dp11
Sat Aug 15, 2020 7:10 pm
Forum: 8-bit acorn hardware
Topic: Master 128 Issue 1/2 differences
Replies: 9
Views: 481

Re: Master 128 Issue 1/2 differences

Thanks for the images
by dp11
Sat Aug 15, 2020 3:44 pm
Forum: 8-bit acorn hardware
Topic: VIDPROC V2 (pin 15) - please explain!
Replies: 33
Views: 1037

Re: VIDPROC V2 (pin 15) - please explain!

please note the high of 3.4v is only at a load of 1mA DC for the S00
by dp11
Sat Aug 15, 2020 1:28 pm
Forum: 8-bit acorn hardware
Topic: Master 128 Issue 1/2 differences
Replies: 9
Views: 481

Re: Master 128 Issue 1/2 differences

Beebmaster thats an Issue 1 PCB.
by dp11
Sat Aug 15, 2020 11:20 am
Forum: 8-bit acorn hardware
Topic: Master 128 Issue 1/2 differences
Replies: 9
Views: 481

Re: Master 128 Issue 1/2 differences

The beeb master images are a bit low res these days.

1024MAK if you could take a high res image the would be great.
by dp11
Sat Aug 15, 2020 11:18 am
Forum: 8-bit acorn hardware
Topic: VIDPROC V2 (pin 15) - please explain!
Replies: 33
Views: 1037

Re: VIDPROC V2 (pin 15) - please explain!

The three diodes set an approx 1.8v rail for internal logic. The X is just biasing the 16Mhz clock.
by dp11
Mon Aug 10, 2020 7:12 am
Forum: 8-bit acorn hardware
Topic: PiTubeHat CoPro and DOS: CTRL-ALT-DEL ?
Replies: 2
Views: 233

Re: PiTubeHat CoPro and DOS: CTRL-ALT-DEL ?

I suspect crtl alt del was too new when dos plus was made.
COPY is the is mapped to the ALT key.

Also just for completeness PiTubeDirect isn't called a Hat as it does not conform to the HAT specification.
by dp11
Sun Aug 09, 2020 9:43 pm
Forum: 8-bit acorn emulators
Topic: MAME: Hybrid Music 5000
Replies: 14
Views: 826

Re: MAME: Hybrid Music 5000

Have a look at Pi1MHz M5000. This does simplify the time slot method to significantly reduce process time.

https://github.com/dp111/Pi1MHz/blob/ma ... emulator.c
by dp11
Sat Aug 08, 2020 10:41 pm
Forum: programming
Topic: Load half a mode 7 screen
Replies: 60
Views: 1765

Re: Load half a mode 7 screen

The simplest way is to split the files into two.

Code: Select all

*load fullscreen 6C00
*save top 6C00 + 200
*save bot 6E00 + 200

#to load a file to the top of screen 
*load file 7C00
#to load a file to the bottom of screen 
*load file 7E00
by dp11
Sat Aug 08, 2020 10:01 am
Forum: 8-bit acorn hardware
Topic: Best value for isolated data bus pull up resistors?
Replies: 4
Views: 321

Re: Best value for isolated data bus pull up resistors?

Depends on your capacitance. Have a look on a scope to see what is happening. Remember every chip also adds capacitance so populate everything socket.
by dp11
Sat Aug 08, 2020 7:50 am
Forum: off-topic
Topic: Advice: Scopes and Bench Power Supplies
Replies: 5
Views: 349

Re: Advice: Scopes and Bench Power Supplies

They cost more some of the UIs are terrible on the older TEK stuff. Also some models have extremely small sample memories. The serial decoders are often better. My view would be get some like the rigol maybe via ebay to understand what you like and don't like and what you require and don't require. ...
by dp11
Fri Aug 07, 2020 7:52 pm
Forum: off-topic
Topic: Advice: Scopes and Bench Power Supplies
Replies: 5
Views: 349

Re: Advice: Scopes and Bench Power Supplies

Depending on how much you want to invest. I like this as cheap scope : https://www.telonic.co.uk/Rigol-DS1054Z-4ch-50MHz-Digital-Oscilloscope-p/ds1054z.htm ( I know to some it isn't cheap , but it is less than what a Beeb was new) . You can software hack it to 100MHz. It has a very deep memory which...
by dp11
Tue Aug 04, 2020 4:38 pm
Forum: general
Topic: SD Card on Fire
Replies: 31
Views: 1453

Re: SD Card on Fire

Splash the cash on another PiZero.
by dp11
Mon Aug 03, 2020 7:23 pm
Forum: 8-bit acorn hardware
Topic: XC95144-100 Development Board
Replies: 17
Views: 748

Re: XC95144-100 Development Board

There is no such thing as too much flux except cost when starting out use as much as you can. Once you get use to the heat and speed required you can skimp on the amount of flux , but it is never zero.
by dp11
Sun Aug 02, 2020 7:29 pm
Forum: 8-bit acorn hardware
Topic: Master 128 Issue 1/2 differences
Replies: 9
Views: 481

Master 128 Issue 1/2 differences

Following on from a comment in VABUG. It appears there isn't actually any documentation of the differences between issue 1 and issue 2 master 128s The follow is my current understanding: The circuits diagrams ( 0143,000/C as found on mdfs ) are for issue 2 PCBs Issue 1 don't have LK11 C28 for Colour...
by dp11
Sun Aug 02, 2020 9:42 am
Forum: 8-bit acorn hardware
Topic: XC95144-100 Development Board
Replies: 17
Views: 748

Re: XC95144-100 Development Board

30cm of cable may work or it may not. If you must then I suggest you put 100R series resistor at the beeb end. Also form a twisted pair with a ground cable connected at both ends. All I can say it good luck. If you what to simplify debugging you have just added another layer of complication.
by dp11
Sat Aug 01, 2020 4:06 pm
Forum: 32-bit acorn hardware
Topic: Repair thread: RiscPC 600
Replies: 26
Views: 1351

Re: Repair thread: RiscPC 600

Might be worth probing vidrq, vidak, sndrq, sndak
by dp11
Fri Jul 24, 2020 7:27 pm
Forum: other vintage hardware, software and languages
Topic: Spectrum PCB foil delamination
Replies: 11
Views: 476

Re: Spectrum PCB foil delamination

Very common in PCBs of the eighties. I wouldn't worry.
by dp11
Thu Jul 16, 2020 11:24 pm
Forum: 8-bit acorn hardware
Topic: PiTubeDirect Problems
Replies: 18
Views: 709

Re: PiTubeDirect Problems

I would try creating a cmdline.txt file on the SDCARD with

Code: Select all

tube_delay=10
by dp11
Thu Jul 16, 2020 1:53 pm
Forum: 8-bit acorn hardware
Topic: PiTubeDirect Problems
Replies: 18
Views: 709

Re: PiTubeDirect Problems

If you have a beeb I would try tube delay in cmdline.txt
by dp11
Sun Jul 12, 2020 1:47 pm
Forum: 8-bit acorn hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 290MHz)
Replies: 1268
Views: 165476

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

Is the right way to fix this to detect the language transfer and if the header isn't arm just ignore the data being transferred.?
by dp11
Sat Jul 11, 2020 5:44 am
Forum: 32-bit acorn hardware
Topic: RISC PC motherboard refurbish
Replies: 13
Views: 625

Re: RISC PC motherboard refurbish

I have one of these, it works very well https://www.peakelec.co.uk/acatalog/esr ... ml#SID=24
by dp11
Tue Jul 07, 2020 9:02 pm
Forum: programming
Topic: Self Modifying Code
Replies: 12
Views: 818

Re: Self Modifying Code

Go for it . The only risk is you might break some emulation, but if you do the emulator needs to be fixed as self modifying code is was used in the 80's . Also *LOAD machinecode 3000 is a simple case of self modifying code. For some cases for real speed I've seen self modifying code in zero page.

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