alford@ecsvax.UUCP (10/13/84)
Has anyone seen soft- or hardware that speeds up the data transfer rate
of the 1541 disk drive to something more reasonable? I have a copy of
the 4 minute disk copy program from Compuserve, and I've timed its track
reads at about 2 seconds, for a data rate of at least 16k bits/sec, if my
arithmetic is right. In normal operation, the transfer rate is about 2k
bits/sec, slower by a factor of 8! I would think that whatever the trick
this program uses, it should be possible to modify it for use with a
DOS wedge, or to insert in the 6502 BIOS of C64 CP/M. This program
definitely reprograms the disk drive. I'd think that if it could be
done once, some clever person out there would have done it again, or
at least have disassembled the 4 minute program to see how it works.
C64 CP/M would be genuinely usable with an 8x disk speedup. I could
send a hex version of this file to anyone who's interested in looking
at it. Please reply if you've heard of anything along these lines.
Thanks,
Ross Alford
{decvax, akgua, ihnp4}!mcnc!ecsvax!alforddoug@terak.UUCP (10/15/84)
[] > Has anyone seen soft- or hardware that speeds up the data transfer rate > of the 1541 disk drive to something more reasonable? I have a copy of > the 4 minute disk copy program from Compuserve, and I've timed its track > reads at about 2 seconds, for a data rate of at least 16k bits/sec, if my > arithmetic is right. In normal operation, the transfer rate is about 2k > bits/sec, slower by a factor of 8!... Some background information: The primary limitation on the speed of the disk drive is that the serial cable is operated at a very low rate (8K bits per sec). This is because the C-64 does not use a USART chip to take 8 bits from the cable and make a byte out of them, but rather requires that the CPU chip receive each individual bit. This worked OK in the VIC-20, but the C-64's CPU chip can be rendered "unconscious" by the VIC-II video chip for up to 50 microseconds at a time. This occurs every 8 scan lines, when the VIC-II needs to look at what characters will be displayed for the next 8 scan lines. So Commodore had to slow down the communications speed on the serial cable so that even when the CPU chip was asleep for 50 microseconds that it wouldn't miss a data bit. This is the difference between a VIC-1540 disk drive and the VIC-1541 drive. The 1541 is slowed down. It is possible to make the C-64/1541 combination run as fast as a VIC-20/1540. First you have to set the bit in the VIC-II chip that causes it to blank the screen (like in cassette saving and loading). Then send the "UI-" command to the disk drive. This sets it in the faster mode. You can now operate at the faster VIC-20 speed. Except your screen will be totally blank. Another way to increase the speed is to transfer large blocks of data in one disk operation. Normally, for each byte you want to read, about half a dozen others are passed back and forth with the disk to select the proper disk drive and file. Hope this provides you with some clues. Doug Pardee -- Terak Corp. -- ...!noao!terak!doug
bllklly@uwmacc.UUCP (Bill Kelly) (10/19/84)
[How about the two latest incompatible Commodores--see Run mag]
1541 speedups were a topic of discussion at the latest Madison Commodore
Club meeting. Unfortunately I have a terrible memory and didn't take
notes. But two pertinent points are:
There's a product recently out called Flash that is a hardware (firmware?)
upgrade to the 1541. Reviews on it were mixed, and the consensus was to
wait for reviews before you take a chance on it. Someone said the speedup
wasn't that impressive.
There's also a program called Quickload, I believe, that loads programs 4
times faster than usual (doesn't help in other types of disk I/O). I don't
know where you can get it...check the ads.
An unrelated aside. Commodore is apparently reluctant to release the Comal
cartridge in the US. Comal is an interpreted language similar to Pascal
with many of the graphics features of Logo (in fact the cartride is claimed
to emulate Logo completely). Commodore is afraid there wouldn't be
sufficient interest in the U.S. If this sounds interesting to you, write a
letter to Commodore and urge them to market it. And if you want to try the
preliminary version of Comal, check any recent issue of Run or Commodore
Microcomputer magazine -- it's only $20.
--
Bill (Regnad Kcin) Kelly
{allegra, ihnp4, seismo}!uwvax!uwmacc!bllklly
1210 West Dayton St/U Wisconsin Madison/Mad WI 53706
"When you have eliminated the impossible, what remains,
however improbable, is the truth."
---Sherlock Holmes' comments on debugging, from his monograph
"The Art of Deduction and Babbage's Analytical Engine"