Bell Labs look like they’ve just opened up a little more of their source-code in the shape of some system commands.
It’s worth a browse just to have a look at how some of these things were implemented.
A quick update, seems that someone has Plan9 running on a raspberry PI.
Here’s a little tid-bit that I’d like to make note of. In a previous MASM32 windows development tutorial, I needed a random number generator and was able to dig this one up from the archives.
First of all, you need to make sure we’re using the 586 instruction set - at least!
; minimum instruction set requirement
.586Shortly, it will become clear why we need the 586 instruction set. To support the random number generator, we need a bit of state in the shape of two double-words.
; calculation state
prng_x DD 0
; current seed
prng_a DD 100711433These two variables allow the random number generator to know where it’s up to for the next iteration. Changing the initial seed of course will change the sequence of random values that are produced by this routine. The actual function that produces the random number look like this:
PrngGet PROC range:DWORD
; count the number of cycles since
; the machine has been reset
rdtsc
; accumulate the value in eax and manage
; any carry-spill into the x state var
adc eax, edx
adc eax, prng_x
; multiply this calculation by the seed
mul prng_a
; manage the spill into the x state var
adc eax, edx
mov prng_x, eax
; put the calculation in range of what
; was requested
mul range
; ranged-random value in eax
mov eax, edx
ret
PrngGet ENDPThere it is. That first instruction RDTSC is what we need to turn the 586 instruction set on for. This mnemonic stands for Read Time-Stamp Counter. It will take the number of cycles since the machine has been reset and put this count into the EDX:EAX pair (as the time stamp counter is a 64bit value). From there some calculations are performed to ensure the consistency of state between random value retrieves and also capping to the requested range.
Simple and it works too!
So, not much of tutorial here - just a neat layout of setup code for a few mode X modes I’ve come across now and then.
First of all, just some formalities. Setting Mode X tweaks to the VGA is a massive port-out exercise. Creating the following macro cut down on my code heaps.
outp MACRO port, value
mov dx, port
mov al, value
out dx, al
ENDMSo you can see, it just gives sending a byte out to a port a bit of syntactical sugar in assembly language. Easy.
The only other piece of formality is, you must have set the video display into MCGA (mode 13) first:
set_mcga:
mov ax, 0013h
int 10h
retOn to the modes.
tweak_160x120:
; --------------------------
; 160x120
;
; pages = 13
; line size = 40
; page size = 19200
; --------------------------
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 07fh
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
outp 03c2h, 0e3h
outp 03d4h, 000h
outp 03d5h, 032h
outp 03d4h, 001h
outp 03d5h, 027h
outp 03d4h, 002h
outp 03d5h, 028h
outp 03d4h, 003h
outp 03d5h, 020h
outp 03d4h, 004h
outp 03d5h, 02bh
outp 03d4h, 005h
outp 03d5h, 070h
outp 03d4h, 006h
outp 03d5h, 00dh
outp 03d4h, 007h
outp 03d5h, 03eh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 043h
outp 03d4h, 010h
outp 03d5h, 0eah
outp 03d4h, 011h
outp 03d5h, 0ach
outp 03d4h, 012h
outp 03d5h, 0dfh
outp 03d4h, 013h
outp 03d5h, 014h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 0e7h
outp 03d4h, 016h
outp 03d5h, 006h
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 003h
outp 03c5h, 000h
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 011h or 020h
outp 03c0h, 0
mov dx, 03dah
in al, dx
outp 03c0h, 012h or 020h
outp 03c0h, 0fh
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
mov dx, 03dah
in al, dx
outp 03c0h, 014h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 80h
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
ret
tweak_296x220:
; --------------------------
; 296x220
;
; pages = 4
; line size = 74
; page size = 65120
; --------------------------
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 7fh
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
outp 03c2h, 0e3h
outp 03d4h, 000h
outp 03d5h, 05fh
outp 03d4h, 001h
outp 03d5h, 049h
outp 03d4h, 002h
outp 03d5h, 050h
outp 03d4h, 003h
outp 03d5h, 082h
outp 03d4h, 004h
outp 03d5h, 053h
outp 03d4h, 005h
outp 03d5h, 080h
outp 03d4h, 006h
outp 03d5h, 00dh
outp 03d4h, 007h
outp 03d5h, 03eh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 041h
outp 03d4h, 010h
outp 03d5h, 0d7h
outp 03d4h, 011h
outp 03d5h, 0ach
outp 03d4h, 012h
outp 03d5h, 0b7h
outp 03d4h, 013h
outp 03d5h, 025h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 0e7h
outp 03d4h, 016h
outp 03d5h, 006h
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 80h
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
ret
tweak_320x200:
; --------------------------
; 320x200
;
; pages = 4
; line size = 80
; page size = 64000
; --------------------------
outp 03c4h, 04h
outp 03c5h, 06h
outp 03d4h, 017h
outp 03d5h, 0E3h
outp 03d4h, 014h
outp 03d5h, 0
ret
tweak_320x240:
; --------------------------
; 320x240
;
; pages = 3
; line size = 80
; page size = 76800
; --------------------------
outp 03d4h, 11h
mov dx, 03d5h
in al, dx
and al, 7fh
mov bl, al
outp 03d4h, 11h
outp 03d5h, bl
outp 03c2h, 0e3h
outp 03d4h, 000h
outp 03d5h, 05fh
outp 03d4h, 001h
outp 03d5h, 04fh
outp 03d4h, 002h
outp 03d5h, 050h
outp 03d4h, 003h
outp 03d5h, 082h
outp 03d4h, 004h
outp 03d5h, 054h
outp 03d4h, 005h
outp 03d5h, 080h
outp 03d4h, 006h
outp 03d5h, 00dh
outp 03d4h, 007h
outp 03d5h, 03eh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 041h
outp 03d4h, 010h
outp 03d5h, 0eah
outp 03d4h, 011h
outp 03d5h, 0ach
outp 03d4h, 012h
outp 03d5h, 0dfh
outp 03d4h, 013h
outp 03d5h, 028h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 0e7h
outp 03d4h, 016h
outp 03d5h, 006h
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
or al, 80h
mov bl, al
outp 03d4h, 11h
outp 03d5h, bl
ret
tweak_320x400:
; --------------------------
; 320x400
;
; pages = 2
; line size = 80
; page size = 128000
; --------------------------
outp 03c4h, 004h
outp 03c5h, 006h
outp 03d4h, 017h
outp 03d5h, 0E3h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 040h
ret
tweak_360x360:
; --------------------------
; 360x360
;
; pages = 2
; line size = 90
; page size = 129600
; --------------------------
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 7fh
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
outp 03c2h, 067h
outp 03d4h, 000h
outp 03d5h, 06bh
outp 03d4h, 001h
outp 03d5h, 059h
outp 03d4h, 002h
outp 03d5h, 05ah
outp 03d4h, 003h
outp 03d5h, 08eh
outp 03d4h, 004h
outp 03d5h, 05eh
outp 03d4h, 005h
outp 03d5h, 08ah
outp 03d4h, 006h
outp 03d5h, 0bfh
outp 03d4h, 007h
outp 03d5h, 01fh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 040h
outp 03d4h, 010h
outp 03d5h, 088h
outp 03d4h, 011h
outp 03d5h, 085h
outp 03d4h, 012h
outp 03d5h, 067h
outp 03d4h, 013h
outp 03d5h, 02dh
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 06dh
outp 03d4h, 016h
outp 03d5h, 0bah
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
or al, 80h
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
ret
tweak_400x300:
; --------------------------
; 400x300
;
; pages = 2
; line size = 100
; page size = 120000
; --------------------------
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 7fh
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
outp 03c2h, 0e7h
outp 03d4h, 000h
outp 03d5h, 071h
outp 03d4h, 001h
outp 03d5h, 063h
outp 03d4h, 002h
outp 03d5h, 064h
outp 03d4h, 003h
outp 03d5h, 092h
outp 03d4h, 004h
outp 03d5h, 067h
outp 03d4h, 005h
outp 03d5h, 082h
outp 03d4h, 006h
outp 03d5h, 046h
outp 03d4h, 007h
outp 03d5h, 01fh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 040h
outp 03d4h, 010h
outp 03d5h, 031h
outp 03d4h, 011h
outp 03d5h, 080h
outp 03d4h, 012h
outp 03d5h, 02bh
outp 03d4h, 013h
outp 03d5h, 032h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 02fh
outp 03d4h, 016h
outp 03d5h, 044h
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 002h
outp 03c5h, 00fh
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
or al, 80h
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
retI will have an update to this post. There are some nuances that I’d much prefer explain to you with a couple of nice code blocks rather than how I’m just going to throw it into the page.
These chunks will be helpful in page selection and optimizing page draws to multiple pages at once.
; setting a page
; activeOffset = vgapage + (page * pageSize / 4);
; enable all planes
; outp 03c4h, 02h
; outp 03c5h, 0fhSome really good references on this topic are
Well, that’s it for now.
As a quick bookmark, this part of the Mesa3D project: Off-screen Rendering.
Looks like it might be a viable option for some of the lower-end hardware I’ve come across lately.
I play a lot of music. I mean a lot of music. Guitar, Bass, Piano, Drums, Harp – what ever I can get my hands on, I’ll give it a go. So, the neurons in charge of keeping my technical side in check may have made their way into the creative side of my brain.
The net result was me creating a project that mashes mathematics, data analysis and music theory into a few classed called musica.
Yeah, basically.. But, I am who I am - so it’ more of a matter of “why not?”.
I’d previously tried building a Ruby on Rails application to give me graphical representations of musically related elements on screen. A scale is a pattern of intervals realised once a root note is put in place. This scale can then be harmonised at every step of the scale by employing every second note from the specific step. How complex these harmonised chords are will depend on how many steps you include in the chords that you build.
The most interesting part of this library, I think, is its distinct lack of database. It has made the code quite verbose in parts but I intend to fix this, even if it does mean employing an intermediary database at a later stage.
The major, harmonic & melodic minor scales (and all of their modes) are statically provisioned. You can use these in code to perform operations like voicing a scale when used in conjunction with a Note object.
Immediately, we can get information about notes:
>>> Notes.by_distance(0)
<musica.notes.Note object at 0x10f961090>
>>> Notes.by_distance(0).__unicode__()
'c'Information about scales:
>>> Scales.scales[0]
<musica.scales.Scale object at 0x10f963090>
>>> Scales.scales[0].name
'Ionian'
>>> Scales.scales[0].intervals
[<musica.intervals.Interval object at 0x10f961950>, <musica.intervals.Interval object at 0x10f9619d0>, <musica.intervals.Interval object at 0x10f961a50>, <musica.intervals.Interval object at 0x10f961a90>, <musica.intervals.Interval object at 0x10f961b10>, <musica.intervals.Interval object at 0x10f961b90>, <musica.intervals.Interval object at 0x10f961c10>]Voicing a scale (in this instance voicing Ionian (major) over C)
>>> steps = Scales.scales[0].voice(Notes.by_distance(0))
>>> for s in steps:
... print 'note: ' + s['note'].__unicode__() + ', interval: ' + s['interval'].short_name
...
note: c, interval: PU
note: d, interval: M2
note: e, interval: M3
note: f, interval: P4
note: g, interval: P5
note: a, interval: M6
note: b, interval: M7Still, we need to get chords harmonising from these voiced scales. These are just patterns after all. An intelligent chord builder would also be of value I think. Something where we don’t have to explicitly map out chord names to interval sets statically. Just knowing that a root, major third and perfect fifth are a major chord.
That’d be a cool calculator, I think.