SoundTrack: ... HAPPY RAVE 4EVA ... RLA / CRG
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Author: Card! Nal / PGC / BD
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Ultrafast formatting disks
Speccy - this is reality.
- Something you look today, it does not matter.
- Yes piss head hit :-(
- Why a black eye?
- And you thought the pot by flying?
(Instead of the epigraph)
Hello, dear readers Deja Vu! C
you again myself. At this time I'll tell you about
quick format TR DOS disks. On
pages Revyushek repeatedly appeared
articles, in which people expressed different ideas at the
expense of formatting track per revolution. Assumptions were
many but they all boil down to one thing - need to format the
track is not full, and very nearly gets to the end and abort
the operation, "a track record." After This should have time to
repositioning drive heads, and before The current track is
finished, ie Prior to joining index pulse, it is necessary to
do everything to prepare for formatting the next track. But the
rub is that the interrupt formatting is almost impossible. A
Why? - You ask. Because the recording track is commonly used
routine at # 3FCA in ROM TR DOS. That's it listing, HL points
to the data:
# 3FCA IN A, (# FF)
AND # C0
JR Z, # 3FCA
RET M
OUTI
JR # 3FCA
It shows that, indeed, yield
carried out by the arrival of the index pulse. But in Rom TR
DOS have another routine to write data to disk. Located it is
at # 20AF:
# 20AF LD B, 1
# 20B1 IN A, (# FF)
AND # C0
JR Z, # 20B1
RET M
OUT (C), D
DJNZ # 20B1
RET
Here we will take it on vooruzhenie.Zdes
immediately evident that the output is possible not only
on the arrival of the index pulse, but when
Register B will be equal to zero. But first, let's count. Drive
spinning discs at a rate of 300ob/min. One turn drive takes 0.2
seconds. On one track is about, 6150 bytes means for writing
one byte to be spent no more than 0.2 * 50 * 70000/6150 = 113.8
cycles. But since Brake is a Spectrum
we assume that the limit of 100 cycles.
So, to use the procedure for
at # 20B1, to speed up
the process of calling this procedure with the required
data in the register D. One irresponsible
People argued that it is impossible, but it
was wrong. You can do this, approximately
as follows:
LD HL, # 3D2F
LD (STACK1 +1), SP
LD SP, ADRTAB
LD C, # 7F
FAQ POP DE
LD B, E
JP (HL)
STACK LD A, # D0; forced interruption
LD C, # 1F
JP (HL)
STACK1 LD SP, 0
RET
Table Format ADRTAB as follows:
ADRTAB DEFB COUNTER; how many bytes to write
DEFB BYTE; bytes to write
DEFW # 20B1
DEFW FAQ; Tag FAQ
...
and so on ... ends with a table like this:
DEFB COUNTER
DEFB BYTE; last byte to write
DEFW # 20B1
DEFW STACK
DEFW # 2A53
DEFW STACK1
The speed of the procedure = 92 cycles,
As you see, is enough time to
time to give sleduyutsy bytes to write
it to disk. Also on track are not recorded in all the 6150
bytes, but 5980. After recording the last sector of the
checksum, formatting track breaks. You can even speed up the
procedure, if the HL Record # 3D30 instead # 3D2F. Speed at
the same time to increase by 4 cycles and was 88 strokes. True
some have argued that some of Spectrum for switching pages-ROM
requires a couple of other CPU cycles. I well imagine how is,
roughly speaking, switching ROMs. PZU'shka TR DOS is enabled
when the bus address, addresses # 3D00 - # 3DFF, in addition,
at this time must be connected to ROM BASIC-48, rather than
BASIC-128, TR DOS otherwise not connect. All are engaged in IC,
and in my CPU cycles are not being. My opinion that the TR DOS
can be safely handled and by # 3D30. Everything should work. I
personally do not heard that someone did not work the game:
DOUBLE XINOX; 48 irons (crack by MAFIA)
or there ZX-FORMAT'y. But in these programs in all used # 3D30.
Saw it myself. I change my mind if I can prove (Or better show)
the reverse. But I digress. Of course, before calling this
program must unleash the drive to position the head, correct
values in the table (number of sectors and tracks), and then
another and be able to read the status register VG'shki
(Suddenly, by a plastic disc). Fully program
formatting I do not give, you will find everything
in the source of the formatter in Appendix
magazine named FASTFORM.H format
assembler ALASM. Now I say that the tablet
ADRTAB not very big, a little less than 1.5Kb.
About the other stuff I will not speak, you
themselves understand everything, download the source code with
detailed comments. Try to reformat the drive and then test it
for quality RDS'koy. It is advisable to use high quality floppy
disk. After all, the actual quality format is not done, but
High speed - 32 seconds!
Finally I want to say one explanation
for some other topic. Some, again unconscious elements are
trying to zapudrit brains, saying the following. Like, for
Scorp'e can directly access the registers of the SH. And for
that to put in the port # 1FFD unit to connect the page
RAM instead of ROM and freely programmable
VG'shku. And I say that so access to registers directly SH
impossible. Sam checked in various ways. Want
wish that the idea should first check
in fact, before so to speak. But
on Scorp'e can easily read the status register of the
controller. Apparently the developers took into account this
fact, and at # 3FF3 flashed command: IN A, (C): RET. That's all.
Bye.
