Search found 1211 matches

by dp11
Sat Nov 28, 2020 6:20 am
Forum: 8-bit acorn hardware
Topic: Choosing a slice of Pi
Replies: 6
Views: 135

Re: Choosing a slice of Pi

Pi4 doesn't really get toasty. Pitubedirect only uses one of the 4 arm cores, doesn't make good use of NEON, doesn't hammer the external memory, etc.
by dp11
Sat Nov 28, 2020 5:50 am
Forum: 8-bit acorn hardware
Topic: Choosing a slice of Pi
Replies: 6
Views: 135

Re: Choosing a slice of Pi

I would say go for Pizero. Pi4s are faster but do you really need the extra performance?
by dp11
Fri Nov 27, 2020 6:56 am
Forum: general
Topic: Raspberry Pi 400
Replies: 50
Views: 1562

Re: Raspberry Pi 400

I see no reason why not. But do be careful about the length of ribbon cable and the end you put your level translator.
by dp11
Wed Nov 25, 2020 1:06 pm
Forum: 8-bit acorn hardware
Topic: Help - Implementing Shadow RAM in CPLD
Replies: 132
Views: 3336

Re: Help - Implementing Shadow RAM in CPLD

have you got any decoupling on vbat and vdd ?
by dp11
Wed Nov 25, 2020 6:05 am
Forum: 8-bit acorn software: other
Topic: MMFS Version 2
Replies: 363
Views: 2479

Re: MMFS Version 2

It strikes me with a little bit of of cleverness you can copy files from FAT on the SDCARD to an MMFS2 drive. If you just DIN fatfile then read sector's from zero you can copy files from FAT to ram then onto a dsd.
by dp11
Sun Nov 15, 2020 5:58 pm
Forum: 8-bit acorn hardware
Topic: Second Failure of Start-up Capacitor C9 on Beeb PSU
Replies: 13
Views: 283

Re: Second Failure of Start-up Capacitor C9 on Beeb PSU

My kit from IFEL (Steve) contained both Suntan and Rubycon capacitors for C9 giving me the choice of which to use. Just to clarify, slightly poor wording on my part, I have no connection to IFEL except as a satisfied customer on a couple of occasions. I should have said "The kit which I purchased f...
by dp11
Sun Nov 15, 2020 4:06 pm
Forum: 8-bit acorn hardware
Topic: Second Failure of Start-up Capacitor C9 on Beeb PSU
Replies: 13
Views: 283

Re: Second Failure of Start-up Capacitor C9 on Beeb PSU

There is a short discussion of the differences on the eBay listing: https://www.ebay.co.uk/itm/Acorn-BBC-Micro-Model-B-Master-128-high-quality-capacitor-kit-extras/223457155695 You aren't really comparing the right rubycon cap surely you should be comparing something like the YXH series ? ESR for t...
by dp11
Sun Nov 15, 2020 6:53 am
Forum: 8-bit acorn hardware
Topic: Second Failure of Start-up Capacitor C9 on Beeb PSU
Replies: 13
Views: 283

Re: Second Failure of Start-up Capacitor C9 on Beeb PSU

Do you have a photo of the second failed capacitor fitted to the psu?
by dp11
Mon Nov 09, 2020 11:52 pm
Forum: off-topic
Topic: Received bad news last week
Replies: 20
Views: 532

Re: Received bad news last week

Sorry for your loss, but its good you can feel you can tell us about it.
by dp11
Wed Nov 04, 2020 1:10 pm
Forum: general
Topic: Raspberry Pi 400
Replies: 50
Views: 1562

Re: Raspberry Pi 400

Yes the CM4 and the I/O board look good, although puzzlingly the I/O board only has 2x USB 2. There are some headers for more USB ports but I don't know if they're 2.0 or 3. CM4IO board doesn't have an xHCI controller so there is no USB3 ports. If you want USB3 you can add one on the PCIe bus, but ...
by dp11
Tue Nov 03, 2020 12:01 pm
Forum: general
Topic: Raspberry Pi 400
Replies: 50
Views: 1562

Re: Raspberry Pi 400

A 4GB Pi has 128K of RAM for every byte of RAM on a 32K Beeb
by dp11
Thu Oct 08, 2020 9:53 pm
Forum: 32-bit acorn software: other
Topic: Compiling ARM BASIC from Source
Replies: 30
Views: 1466

Re: Compiling ARM BASIC from Source

Dave , if you want a chat about memory map I'm happy to help. Pi1MHz makes most of the memory cached and uses cache flushes when required. I think I have just thought of a bit more that can be cached in Pi1MHz.
by dp11
Sun Sep 20, 2020 11:15 am
Forum: programming
Topic: Tube coding 101! Help wanted please.
Replies: 36
Views: 1816

Re: Tube coding 101! Help wanted please.

I had a prototype tube splitter back in the day. It was really meant for the ABC workstation I think. It was sort of L shaped around a 6502 second processor.
by dp11
Sun Sep 20, 2020 9:54 am
Forum: 8-bit acorn hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 290MHz)
Replies: 1272
Views: 171711

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 290MHz)

I think the startup code should ask the gpu how much memory there is. In Pi1MHz this is done in C for PiTubeDirect I think it can be done in assembler before the stacks and vectors are positioned. I'd sort of like not to go down the route of too many different kernels. Pi4 users would then want 1, 2...
by dp11
Wed Sep 16, 2020 11:47 pm
Forum: 8-bit acorn hardware
Topic: New SCSI Host Adaptor
Replies: 121
Views: 6882

Re: New SCSI Host Adaptor

Remember 74hct245 can't drive 24mA so won't work.
by dp11
Wed Sep 16, 2020 10:34 pm
Forum: 8-bit acorn hardware
Topic: Help! Master 128 Resurrection (hopefully)
Replies: 20
Views: 1161

Re: Help! Master 128 Resurrection (hopefully)

You do can try a 74LS04 but it might not work, you should really should use 74S04
by dp11
Wed Sep 16, 2020 10:29 pm
Forum: 8-bit acorn hardware
Topic: New SCSI Host Adaptor
Replies: 121
Views: 6882

Re: New SCSI Host Adaptor

SCSI Bus is designed to be driven with an open collector drive. The terminator is designed to terminate the bus at typically 2.85v. One of the reasons for open collector is if multiple devices are on the bus with the same IDs there won't be a bus conflict. Input levels need to be : Vih >2v , ViL<0.8...
by dp11
Wed Sep 16, 2020 8:05 am
Forum: 8-bit acorn hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 290MHz)
Replies: 1272
Views: 171711

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 290MHz)

The cores written in c show the greatest performance increase with the Pi4 e.g lib6502
by dp11
Tue Sep 15, 2020 10:00 pm
Forum: 8-bit acorn hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 290MHz)
Replies: 1272
Views: 171711

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 290MHz)

As the extra memory isn't used, the Pi4 can just be the cheapest ( 2Gbytes @ £35) Also some people have over clocked the Pi4 for extra performance
by dp11
Tue Sep 15, 2020 11:33 am
Forum: 8-bit acorn hardware
Topic: Help! Master 128 Resurrection (hopefully)
Replies: 20
Views: 1161

Re: Help! Master 128 Resurrection (hopefully)

just spotted it looks like the scope has a 20MHz bandwidth limit filter now on channel 1 can you turn that off.
by dp11
Tue Sep 15, 2020 11:32 am
Forum: 8-bit acorn hardware
Topic: Help! Master 128 Resurrection (hopefully)
Replies: 20
Views: 1161

Re: Help! Master 128 Resurrection (hopefully)

Excellent now try probing pin 2 . If that doesn't give you a signal and there is no obvious signs of damage I think you need a new 74S04 .
by dp11
Mon Sep 14, 2020 2:15 pm
Forum: 8-bit acorn hardware
Topic: Help! Master 128 Resurrection (hopefully)
Replies: 20
Views: 1161

Re: Help! Master 128 Resurrection (hopefully)

Excellent can you now go back and look at the clock pins now the scope is setup in a suitable way
by dp11
Mon Sep 14, 2020 2:35 am
Forum: 8-bit acorn hardware
Topic: Help! Master 128 Resurrection (hopefully)
Replies: 20
Views: 1161

Re: Help! Master 128 Resurrection (hopefully)

I'd like to see how the scope displays it. The scope probes should be set to X10. I don't know how the scope does its vertical maths. But what you want is to adjust the the vertical gain and positioning of the trace to be say 5 divisions different from nothing connected to the probe tip. The go back...
by dp11
Sun Sep 13, 2020 7:22 pm
Forum: 8-bit acorn hardware
Topic: Help! Master 128 Resurrection (hopefully)
Replies: 20
Views: 1161

Re: Help! Master 128 Resurrection (hopefully)

Can i have a scope trace of pin 14 too the 5v pin.

To see the clocks the time base needs to be be some like 0.1us per division.
by dp11
Tue Sep 08, 2020 2:40 pm
Forum: 8-bit acorn hardware
Topic: Help! Master 128 Resurrection (hopefully)
Replies: 20
Views: 1161

Re: Help! Master 128 Resurrection (hopefully)

Can you post a picture of your scope showing nothing?
by dp11
Mon Sep 07, 2020 7:40 pm
Forum: 8-bit acorn hardware
Topic: Help! Master 128 Resurrection (hopefully)
Replies: 20
Views: 1161

Re: Help! Master 128 Resurrection (hopefully)

Firstly are you an experienced scope user ?

What do you see at pin1 and Pin 13 of IC43
by dp11
Thu Sep 03, 2020 11:17 pm
Forum: 8-bit acorn hardware
Topic: [SOLVED] Wobbly Clock
Replies: 10
Views: 624

Re: Wobbly Clock

Set the trigger position to the middle of the screen instead of a 22mS delay will also help. Also make sure the ground lead of the scope is very short ( don't use the ground lead that come with the scope) and is connected to IC43 pin7 if you really want to measure the clock accurately.

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