Search found 282 matches

by mikeb
Tue Feb 16, 2021 4:55 pm
Forum: Hardware hacks and extensions
Topic: DRAMARDUINO - Dram tester with Arduino
Replies: 25
Views: 26766

Re: DRAMARDUINO - Dram tester with Arduino

Interesting... My knowledge of digital electronics is at novice level at best, so bare with me, but doesn't 200ns translate into 5Mhz? 200ns would be 5MHz if it was a simple period to frequency conversion. 200ns is how long it takes from presenting a row-column address pair and saying "READ!" to va...
by mikeb
Sat Feb 13, 2021 5:48 pm
Forum: Hardware hacks and extensions
Topic: DRAMARDUINO - Dram tester with Arduino
Replies: 25
Views: 26766

Re: DRAMARDUINO - Dram tester with Arduino

If you have slow ram chips, and you use them only from $0000 to $B4000 and from $C000 to $FFFF, where only the 6502 is actually doing active reads, using fast chips for the area frequently accessed by the ULA, would that work? Good thought! As Kenneth said -- and definitely not under current hardwa...
by mikeb
Fri Feb 12, 2021 5:33 pm
Forum: Hardware hacks and extensions
Topic: DRAMARDUINO - Dram tester with Arduino
Replies: 25
Views: 26766

Re: DRAMARDUINO - Dram tester with Arduino

They are TMS4164 -20 NL, date code AP8432 They seem to be genuine, rubbing with IPA and acetone did not reveal anything. They are obviously second hand with solder marks on their pins small scratches here and there. Oh, and I confess, I bought them for a Sinclair Spectrum and testing them on it. 😊 ...
by mikeb
Thu Feb 11, 2021 4:51 pm
Forum: Hardware hacks and extensions
Topic: DRAMARDUINO - Dram tester with Arduino
Replies: 25
Views: 26766

Re: DRAMARDUINO - Dram tester with Arduino

I have a set of TI 6154 chips I bought from China Skipping past the obvious objections regarding fakes, and relabelled chips, what is the FULL numbering from the top of the chip? Often, the part number is immediately followed by a speed indication, and there are plenty of 4164-like chips that are t...
by mikeb
Tue Feb 09, 2021 5:19 pm
Forum: Hardware hacks and extensions
Topic: DRAMARDUINO - Dram tester with Arduino
Replies: 25
Views: 26766

Re: DRAMARDUINO - Dram tester with Arduino

... further thought! In an actual Oric, the memory test relies on this "missing address line" situation to distinguish between a 4164 (64k/48k Oric) and a 4116 (16k Oric) bank With the quarter size DRAM chip (16K), now there is nowhere for A7 to go. So whether the row/col address bit 7 is high or lo...
by mikeb
Mon Feb 08, 2021 4:59 pm
Forum: General Discussion
Topic: ORIC NEXT
Replies: 36
Views: 2754

Re: ORIC NEXT

- Upgrade the ULA to add registers allowing to move the "display window" - Upgrade the ULA to add registers to redefine the 8 colors by remapping them with a custom palette that can be changed by the user While you're in there tinkering with the ULA :- A parallel attributes mode! That will stop the...
by mikeb
Mon Feb 08, 2021 4:49 pm
Forum: Hardware hacks and extensions
Topic: DRAMARDUINO - Dram tester with Arduino
Replies: 25
Views: 26766

Re: DRAMARDUINO - Dram tester with Arduino

if I put a 4164 and test it as 41256, it still passes OK, and strangely it also takes as long as a real 41256. Shouldn't it sort of "hit a wall" and return an error when the address incrementing loop goes over XA7 and come to a non-existent XA8 bit? Hello! I suspect what you're doing is testing the...
by mikeb
Sat Feb 06, 2021 7:04 pm
Forum: Hardware hacks and extensions
Topic: TSN 1-2450A instead of LM7905
Replies: 27
Views: 5049

Re: TSN 1-2450A instead of LM7905

I've no idea what the Arduino circuit is doing (or trying to do), so won't comment on that too much -- I can't think of a good reason to drive the ROMDIS low at the same time as reset, while RESET is low the 6502 is dead anyway, so won't see the ROM whether it's there or not. I think the mess you se...
by mikeb
Sat Feb 06, 2021 6:56 pm
Forum: Mags and books
Topic: OUM magazine scans...
Replies: 84
Views: 25289

Re: OUM magazine scans...

What a blast looking through the early OUMs -- I never actually saw the first 20 odd issues when they originally came out, and no longer have full paper versions of those up to 64 anyway. Just to say if Dave Utting is still looking for that ULA circuit diagram (£20 reward rising to £50) I can help h...
by mikeb
Fri Feb 05, 2021 5:41 pm
Forum: Hardware hacks and extensions
Topic: TSN 1-2450A instead of LM7905
Replies: 27
Views: 5049

Re: TSN 1-2450A instead of LM7905

As for the capacitor, any 10uF small electrolytic, rated at 10v to 16v should fit in there. Modern electrolytics tend to be slightly smaller, value/voltage being the same, than older ones. It's not under any particular stress (temperature, heavy currents) like those used in switch mode power supplie...
by mikeb
Fri Feb 05, 2021 5:33 pm
Forum: General Discussion
Topic: Hello from Bristol
Replies: 29
Views: 2843

Re: Hello from Bristol

# Everybody's talking 'bout
Cumulus and Erebus,
Cumana DOS and BD-DOS...
USB and cards (SD)
it's all too much technology ...
Symoon wrote:
Thu Feb 04, 2021 11:09 pm
All I aaaaam saaaay-iiiiing, is giiiive taaaapes a channnnce ;)
by mikeb
Tue Feb 02, 2021 4:39 pm
Forum: Operating systems, utilities and other serious software
Topic: dflat language update
Replies: 72
Views: 7062

Re: dflat language update

- dim a$[5,4]: I should be clearer - but arrays start from index 1 not 0 :-) - input a$: Not sure I have understood the problem? If you type in the quotes, it is correct for it to be captured as part of the input - or something else you are raising? It seems like the confusion over array-counting i...
by mikeb
Thu Jan 14, 2021 6:19 pm
Forum: General Discussion
Topic: FebrORIC?
Replies: 8
Views: 1471

Re: FebrORIC?

mmu_man wrote:
Wed Jan 13, 2021 5:55 pm
Hmm, riiiight… not sure the pun is as catchy though.
OK, let's compromise! Do it through May and June, call it "Mayjoric" :)
by mikeb
Fri Dec 25, 2020 4:58 pm
Forum: 6502 assembly coding
Topic: Oric Atmos ROM 1.1b Disassembly - browsable listing by [raxiss]
Replies: 3
Views: 1869

Re: Oric Atmos ROM 1.1b Disassembly - browsable listing by [raxiss]

Excellent resource, and what a Xmas gift! Already saved for posterity! :) Note that at #E43A ... "trigonometric function data" ... is it time to acknowledge the easter egg? perkin (~)> echo "MICROSOFT" | rev | hexdump -C 00000000 54 46 4f 53 4f 52 43 49 4d # Hi bits, hi bits, other than that it fits...
by mikeb
Thu Dec 10, 2020 4:38 pm
Forum: Hardware hacks and extensions
Topic: IJK-egopad the joypad for Oric by [raxiss]
Replies: 32
Views: 5728

Re: IJK-egopad the joypad for Oric by [raxiss]

Hi all Why don't you have launched some sells with paypal friends process, to reduce costs Further to the answer given by @iss, using Paypal "Send payment to my friend" to pay for goods and services is a red-flag for lots of people, it is the hallmark of scammers and conmen who have no intent to pr...