Search found 1126 matches

by SarahWalker
Wed Jan 16, 2019 6:28 pm
Forum: hardware
Topic: Romcs* observations
Replies: 5
Views: 169

Re: Romcs* observations

Experimental observations -- this code: MOV R0, #&3800000 .L LDR R1, [R0] B L ... results in Romcs* looping through this pattern: 0.35us low 0.15us high (B L) 0.1us low 0.15us high 0.1us low 0.27us high Presumably that's actually something like: 0.25us (2 clocks) - Read 0x3800000 0.1us + 0.15us (2 ...
by SarahWalker
Tue Jan 08, 2019 8:32 am
Forum: emulators
Topic: Arculator & Risc OS 2.0
Replies: 2
Views: 180

Re: Arculator & Risc OS 2.0

Not in v0.99 unfortunately. The next version (which will be out this year! Honest!) will have both ST-506 and IDE podule emulation.
by SarahWalker
Sun Jan 06, 2019 8:45 pm
Forum: wanted
Topic: Acorn A3000 ARM 3
Replies: 23
Views: 612

Re: Acorn A3000 ARM 3

I suspect if you'd spent £500 on an FPA, the question wouldn't be 'what software can use the FPA' but 'what software is actually noticeably improved by having an FPA'? Which owing to the chicken and egg situation regarding floating point on the Arc would be very little!
by SarahWalker
Sun Jan 06, 2019 11:52 am
Forum: wanted
Topic: Acorn A3000 ARM 3
Replies: 23
Views: 612

Re: Acorn A3000 ARM 3

Not a lot :) There's not much point writing FPU dependent software if no one owns one. I ended up using POVray to test Arculator's FPA emulation as there's so little else that exercises it.

eBay is up to three chips now. And two of them are £500!
by SarahWalker
Thu Jan 03, 2019 6:04 pm
Forum: wanted
Topic: Acorn A3000 ARM 3
Replies: 23
Views: 612

Re: Acorn A3000 ARM 3

Cutter wrote:
Thu Jan 03, 2019 5:56 pm
2. Your chances of finding an FPA, even from CJE Micros, are basically nil
Surprisingly, they do currently claim to have one, if you have £250 burning a hole in your pocket :shock:

They also list A3000 ARM3 upgrades, at a typical CJE price.
by SarahWalker
Thu Jan 03, 2019 4:06 pm
Forum: general
Topic: Date of last (final) use of BBC Micros in classrooms?
Replies: 16
Views: 416

Re: Date of last (final) use of BBC Micros in classrooms?

We definitely still had a BBC per classroom when I left primary school, in 1998, and they were still being actively used. There were Beebs at my secondary school, for at least the first couple of years, though I don't remember ever using them; though Arcs were still in use at that point. We did late...
by SarahWalker
Mon Dec 31, 2018 5:02 pm
Forum: other vintage computer hardware, software and games
Topic: Old School PC Hardware Clear Out.
Replies: 10
Views: 453

Re: Old School PC Hardware Clear Out.

I thought Imagination were only responsible for the Matrox M3D (PowerVR PCX2)? The Mystique and G400 were Matrox's own in-house designs.
by SarahWalker
Mon Dec 31, 2018 10:42 am
Forum: emulators
Topic: 6522 VIA emulation: T1LH writes vs. T1 interrupt
Replies: 11
Views: 372

Re: 6522 VIA emulation: T1LH writes vs. T1 interrupt

I think we've already established that I had no idea what I was doing when writing B-em's VIA code.
by SarahWalker
Wed Dec 26, 2018 5:40 pm
Forum: emulators
Topic: Sound filter for the built-in sound
Replies: 2
Views: 168

Re: Sound filter for the built-in sound

B-em's 'sound filter' is attempting to emulate the characteristics of the internal speaker rather than just the board level filtering. The speaker is quite lacking in bass!
by SarahWalker
Sun Dec 23, 2018 11:09 am
Forum: hardware
Topic: ARM1 versions / batches
Replies: 7
Views: 496

Re: ARM1 versions / batches

Even if they aren't compatible, it's entirely possible that the boards could have been reworked. They'd need some rework anyway, to allow for the MEMC1 w/ARM2 workarounds.
by SarahWalker
Tue Dec 18, 2018 6:59 pm
Forum: hardware
Topic: ARM1 versions / batches
Replies: 7
Views: 496

Re: ARM1 versions / batches

Most of pictures I have been able to find have been of the same batch of chips, dated week "8625", and labelled "AUTUMN" (is that a code name or a season?) Codename. My next question is about the A500 computer (not to be confused with the A500 second processor). I originally had the impression that...
by SarahWalker
Mon Dec 17, 2018 6:54 pm
Forum: hardware
Topic: VL2304PS-QC - ANNA
Replies: 24
Views: 808

Re: VL2304PS-QC - ANNA

You need MEMC1As for that - the original MEMC doesn't have support for dual chips.
by SarahWalker
Mon Dec 03, 2018 6:10 pm
Forum: emulators
Topic: More interesting 6522 VIA emulation discrepancies
Replies: 28
Views: 637

Re: More interesting 6522 VIA emulation discrepancies

I think part of the mess in B-em's 6502/VIA timing was to deal with the case where an interrupt fired in the same cycle as a VIA read/write that would clear that interrupt; there's a one cycle delay between the VIA access and the 6502 acknowledging that the IRQ line is no longer firing, meaning that...
by SarahWalker
Sat Dec 01, 2018 1:35 pm
Forum: emulators
Topic: Testing for deterministic NMI timing
Replies: 12
Views: 328

Re: Testing for deterministic NMI timing

The B+ 1MHz decoding is the same as the B, so the FDC is also 2 MHz. The Master's decoding is hidden in IC31 so it's not immediately obvious which addresses cause clock stretching.
by SarahWalker
Sat Dec 01, 2018 1:24 pm
Forum: emulators
Topic: Testing for deterministic NMI timing
Replies: 12
Views: 328

Re: Testing for deterministic NMI timing

Also, both b-em and jsbeeb (which copies the FEslowdown table verbatim) consider 0xFE20 - 0xFE3F and 0xFE80 - 0xFE9F 2Mhz accesses regardless of whether there's an i8271 or wd1770 present. Could be that's corrent for i8271 but not wd1770. Although I had not noticed that clock being stretched out to...
by SarahWalker
Wed Nov 28, 2018 7:29 pm
Forum: emulators
Topic: Default sn76489 sound chip state
Replies: 13
Views: 340

Re: Default sn76489 sound chip state

It's the other way round - a 6502 2P setup does the 'burr' but doesn't do the CHR$(7) beep.
by SarahWalker
Wed Nov 28, 2018 5:42 pm
Forum: community projects
Topic: How many sold? German tank problem:serial nums wtd
Replies: 295
Views: 54484

Re: How many sold? German tank problem:serial nums wtd

Lets see, here's my stuff:- Electron: 07-ALA01-0293089 Can you double check this one please? It's 100,000 out from the current highest 07-ALA01 serial! Also, for the Compact, could you post the keyboard serial as well as the disc box serial? I'm using the former to track numbers as there seem to be...
by SarahWalker
Wed Nov 28, 2018 2:43 pm
Forum: emulators
Topic: Default sn76489 sound chip state
Replies: 13
Views: 340

Re: Default sn76489 sound chip state

No, the Master takes longer to silence it, as the initial boot up stage is longer (at least on MOS 3.20). The time between silencing and printing the startup message (containing the second beep) is similar on both machines. My Master gives ~900 ms of initial tone, ~50 ms of silence followed by ~300 ...
by SarahWalker
Wed Nov 28, 2018 2:31 pm
Forum: emulators
Topic: Default sn76489 sound chip state
Replies: 13
Views: 340

Re: Default sn76489 sound chip state

So to summarise, I think this is an analogue problem - it looks like the sound chip is just outputting square waves at the lowest frequency. This would probably explain why the initial beep sounds different on different machines.
by SarahWalker
Wed Nov 28, 2018 2:29 pm
Forum: emulators
Topic: Default sn76489 sound chip state
Replies: 13
Views: 340

Re: Default sn76489 sound chip state

Okay, scope is showing a normal looking (if very noisy!) 122Hz square wave for the most part. The noise frequencies do change over the course of the beep, and in the early stages look to be in the audible spectrum, which may explain some of the phasing? Otherwise most of the sound looks to be the re...
by SarahWalker
Wed Nov 28, 2018 2:07 pm
Forum: emulators
Topic: Default sn76489 sound chip state
Replies: 13
Views: 340

Re: Default sn76489 sound chip state

I've just sampled the startup of my Master. The base frequency is 122 Hz - the lowest frequency the SN76489 can generate, as expected. The waveform is interesting though - obviously it's being filtered, but it looks like the positive peak is 1/15th of the total period, implying that indeed periodic ...
by SarahWalker
Tue Nov 27, 2018 5:27 pm
Forum: emulators
Topic: Can someone try some simple 6522 VIA queries for me on a real BBC?
Replies: 34
Views: 718

Re: Can someone try some simple 6522 VIA queries for me on a real BBC?

Ah, true. Missed that in my flick through the 6522 datasheet.
by SarahWalker
Tue Nov 27, 2018 4:46 pm
Forum: emulators
Topic: Can someone try some simple 6522 VIA queries for me on a real BBC?
Replies: 34
Views: 718

Re: Can someone try some simple 6522 VIA queries for me on a real BBC?

Latching's supported on both ports, via CA1/CB1 and enabled/disabled by bits 0 and 1 of the ACR. You may be thinking of handshaking? Port A can be accessed without handshaking (via &FExF), while port B can't.
by SarahWalker
Sun Nov 25, 2018 12:07 pm
Forum: emulators
Topic: Can someone try some simple 6522 VIA queries for me on a real BBC?
Replies: 34
Views: 718

Re: Can someone try some simple 6522 VIA queries for me on a real BBC?

Long story: jsbeeb and b-em differ on the handling here. You can see different responses in some of the above commands, although others are the same because MOS initializes some but not all of those registers. As a consequence, jsbeeb can't run Snapper (it hangs at game start after drawing the leve...
by SarahWalker
Mon Nov 19, 2018 4:26 pm
Forum: other vintage computer hardware, software and games
Topic: Vintage Collections
Replies: 47
Views: 1303

Re: Vintage Collections

Stop making me jealous! :cry:
by SarahWalker
Mon Nov 19, 2018 4:22 pm
Forum: other vintage computer hardware, software and games
Topic: Vintage Collections
Replies: 47
Views: 1303

Re: Vintage Collections

trixster wrote:
Sun Nov 18, 2018 11:11 am
Atari Falcon (060)
I hate you.




(seriously though, I'd love a Falcon, but prices are just silly. I'll just have to settle for using my STE. While crying)
by SarahWalker
Mon Nov 19, 2018 4:20 pm
Forum: other vintage computer hardware, software and games
Topic: Vintage Collections
Replies: 47
Views: 1303

Re: Vintage Collections

My collection would probably seem relatively small here! Acorn A3000 (+4MB RAM, 80MB hard drive, broken keyboard) Acorn A4000 (motherboard only. Floppy controller doesn't work) Acorn BBC Master 128 Acorn Electron (until I can get rid of it!) Acorn R260 (8MB RAM, Acorn SCSI w/SCSI2SD) Atari 520STE (+...
by SarahWalker
Thu Nov 08, 2018 6:19 pm
Forum: hardware
Topic: MEMC nibble mode ROM access / ROM emulation
Replies: 4
Views: 276

Re: MEMC nibble mode ROM access / ROM emulation

steve3000 wrote:
Thu Nov 08, 2018 12:39 am
As I recall the ROM access speed on startup is always the slowest - 450ns.
On MEMC reset, yes. RISC OS will measure memory speed during POST and choose a more appropriate setting; on an 8 MHz machine it will select 200ns.
by SarahWalker
Thu Nov 01, 2018 7:39 pm
Forum: software
Topic: RISC OS relicensed: now under Apache 2.0!
Replies: 81
Views: 2581

Re: RISC OS relicensed: now under Apache 2.0!

I am watching the thread but I shall remain an 8 bit’ter I think. But what I would say is that very few OS have made the transitioning to a ‘modern OS’ in the form they started. What I mean by this is. Linux is pretty much was written from the ground up from the 90s, windows/dos was pretty much rew...
by SarahWalker
Thu Nov 01, 2018 6:11 pm
Forum: software
Topic: RISC OS relicensed: now under Apache 2.0!
Replies: 81
Views: 2581

Re: RISC OS relicensed: now under Apache 2.0!

However it seems from your last post that this is one of many things you think ROOL should be enabling, and that by "retro" you just mean that RISC OS shouldn't be considered a commercial project to shepherd into the future, but rather something to preserve and enable people to tinker with. Retro i...