Spectrum Computing

sn3j

test HL = 0x3300 xor A --> a == 0 sub L --> 0x00 - 0x00 --> not carry sbc A,A --> A = 0x00 cpl --> A = 0xFF or H --> fail, because H does not depend and the result will be less than or equal to 0 Do I understand correctly? Argh - right, this is not working with positive high-bytes... too bad. :| Id...

sn3j

but than it is slower than 24ts case. 4*5+10=30. might be useful if HL cannot be destroyed, though. but then we have 18/32 version, which is not much slower, and sometimes faster. still, might be useful for stable timings. Yes, and maybe A is already 0 from a previous operation which would allow us...

sn3j

Antonio Luque wrote: ↑Thu Apr 25, 2024 12:36 pm This takes 26ts, but preserve HL:
Code: Select all
xor a
sub l
sbc a,a
sub h
jp m,GreaterThan0

ketmar wrote: ↑Thu Apr 25, 2024 1:13 pm sadly, this doesn't work with $8000. that pesky $8000 again!

This could be fixed by:

Code: Select all

xor a
sub l
sbc a,a
cpl
or h
jp m,LessOrEqual0

sn3j

Yet another one:

Code: Select all

ld a, h
add a
jp c LE_0
jp nz GT_0
; deal with cases 0..255 here
or l
jp z LE_0

Average would be something along 23.05 T.

sn3j

Here's another one:

Code: Select all

ld a, h
add a
jr c LE_0
or l
jr z LE_0

which is 31T for Zero, 20T for negative numbers (50% of all cases) and 26T for the positive numbers.
Average should be 23T, depending on how your cases are distributed.

sn3j

_dw wrote: ↑Thu Apr 25, 2024 9:28 am the first one is identical, but the second code does something different than you expect. Because 0x8000 will underflow into positive numbers.

yes this is not right, I'll remove it from my post... thank you

sn3j

Maybe if you take the upper part after a DEC and check for bit 7? Something like posted by @_dw above -

Code: Select all

ld a h
dec hl
or h 
jp m LE_0

and add an INC HL before jumping if you need the original value.

sn3j

Music Entertainer - Homecomputer 1984/12 p 35
Can't verify though as no PDF for that issue is available.

Loading screen from the TZX:

sn3j

Ops, this magazine was duplicated by mistake! This is the correct link, including these type-ins: https://spectrumcomputing.co.uk/issue/10463/Happy_Computer/1 EDIT: It seems Happy Computer was originally called "Hobby Computer" in the first issue only. ok I've found the issue number for 8...

sn3j

PS: Regarding German titles, do you know where to find these? https://spectrumcomputing.co.uk/list?group_id=1055&lang=german No idea. I've found a full scan of Hobby-Computer 1983/11 in my download folder, it's not in your database. https://drive.google.com/file/d/11E_W1lePVps-d3Y1B8Tp13nJOOMWB...

sn3j

Please mark it as starting at page 17. That's not exactly accurate, but it's the only page reference we have. done Hupschraubär Pilot - Happy-Computer 84/11 p 74 Manic Train - Computer Kontakt 85/03 p 29 Mensch ärgere Dich nicht - Happy-Computer 84/09 p 40 I see that Neil Parsons already did Hunter...

sn3j

Prophyt wrote: ↑Tue Apr 23, 2024 10:20 amCastle Master

yes

sn3j

Graphik - Heim-Computer 1983/11 p 40 (40 in pdf) Hinterhalt - Heim-Computer 1983/12 p 43 (47 in pdf) Tischdecken - Happy-Computer 1984/07 p 57 (55 in pdf) Der Sagenhafte Schatz des Drachen Mordor: The listing appears to be on a large poster (inside the issue), so no page number. Also, there's no PDF...

sn3j

No. Zooming...

sn3j

not Klax

The game had several big reviews and wasn't mentioned in this thread so far.

sn3j

SteveSmith wrote: ↑Mon Apr 22, 2024 3:10 pm Geoff Capes?

nope

sn3j

Yay!

Next up. This time it's in-game.

sn3j

Rogue

sn3j

My Speccy came bundled with Pogo. It reminded me of the drawings by M.C.Escher that we were talking about in the school in arts.
The game took more than 5 minutes to load which was embarassing as it subsequently crashed (turned out my board had an error and needed replacement).

sn3j

Thank you for commenting Joefish and Timmy . Here's my hacky solution to get a file loaded from code: Set up a 34-byte area with the following data: [0] 3 - this byte tells we're requesting a CODE/SCREEN$ file [1..10] - the name of our file, padded with blanks if less than 10 chars [11..12] - reques...

sn3j

There's a 2nd trap in the ROM at $63a (1594), this is where the file name is taken from by BASin for the next LD_BYTES call.
Am I supposed to call this trap from assembler? It's a bit clumsy to mock all up.

sn3j

I'm trying to load a code block from my assembler routine without the print output to the screen. So I've prepared the 17-byte header in IX and called LD_BYTES at ROM $556. Behind that header I reserved the usual 17-byte space for the header to be received. Address $556 is being trapped by BASin/Bas...

sn3j

sn3j

Could you calculate the square root less often or not at all if you used a different admissible heuristic function? You could presumably use something which is faster to calculate but which meets the criterion of never overestimating the cost of reaching the goal? If the estimation is too far off y...

sn3j

A hacky way of getting this distance between two 2d points is this determine largest and smallest values from x,y length = largest + (smallest>>1) gives a worst case 12% error if smallest >= (largest>>3) then length = largest + (smallest>>1) - (largest>>3) gives worst case ~6% error but mostly <2% ...

Spectrum Computing

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