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Jeff Parsons 2017-07-23 16:04:59 -07:00
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_posts/2017-07-21-retroreview-speedup.md
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@ -208,9 +208,23 @@ head settling times are rarely simulated. As I suggested in my [last blog post]
degree of authenticity that all emulators should strive for, and PCjs emulators are no exception to that rule -- I
just haven't gotten around to it yet.
### "IBM Updates DOS to 1.10"
In the very next issue of PC Magazine (August 1982), there's an article titled
"[IBM Updates DOS to 1.10](https://books.google.com/books?id=WYnHD9WSWdAC&lpg=PA110&ots=QlUklzAI8s&dq=pc%20magazine%20%22IBM%20Updates%20DOS%20To%201.10%22&pg=PA111#v=onepage&q&f=false)"
which includes a section on disk I/O performance and the fate of `SPEEDUP`:
> The speed of the disk I/O has been increased. Although IBM has not published any specific figures,
improvement in disk access appears to be 100 percent. Using the format command as a baseline, DOS version 1.0
formatted a single-sided diskette in 34 seconds, while DOS 1.10 formatted a single-sided diskette in 19 seconds,
including the time necessary to provide improved specification printout upon completion of the format process.
> SPEEDUP.COM, a patch to DOS 1.0 that performed the same function, is no longer needed in DOS 1.10, and any
attempt to use it in the new DOS will result in program errors or unpredictable results.
### Epilogue
There were some nice side benefits to debugging the problems introduced by `SPEEDUP`.
There were some nice side benefits to debugging the problems uncovered by `SPEEDUP`.
First, when attempting to `LIST` a BASIC program to a serial port, I discovered that BASIC depends on the port
generating a "Transmitter Holding Register Empty" interrupt after outputting each byte, and that I had never actually