ZX Computings - OpenLibra

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Benchmarks
Testing
your
ZX81
speed
Henry Budgett and Tim Hartnell
look at the 'standard' series of
benchmark tests and apply them
to the ZX81 to see how well it
performs. Try the tests yourself
and see if your machine
measures up.
There are a number of ways to establish the efficiency of a computer,
and the tests performed are generally called 'benchmarks'.
Each set of these standard tests tries out a function or functions of
the computer, and produces a measureable result which can be
compared with other computers performing similar tasks.
The most commonly used tests in the microcomputer world are
those introduced way back in 1977 by the Yankee magazine
KILOBAUD. While they're not particularly rigorous, they do offer a
quick and simple solution to the problem of checking out how well
the computer performs certain arithmetic functions.
The speed of processing depends on the speed of the microprocessor's
clock. In the ZX81, the BASIC runs at 3.25 MHz.
There are eight benchmarks in the series. Apart from the last
one — which requires the presence of certain mathematical functions
and demands floating-point numbers — you'll be able to run a
version of them on the ZXBO. Each test should be run and timed 10
times, then an average of the results obtained.
The first test is a simple loop program that sets up a FOR . . .
NEXT loop of 1000 counts. This, and the other tests, waits until a
key is pressed after pressing RUN before starting the program. You
enter RUN, then press NEWLINE, and then touch any key (except
BREAK) as you start your timing. Lines 5 and 10 in each program
ensure that the program waits until la) you've taken your finger off
the RUN key (line 5) and then until you've pressed any key (line
10). You'll obviously have to omit these lines on the ZXBO. You
stop timing when the zero appears in the top left-hand corner of the
screen.
The tests are particularly fascinating if you can run them on
another computer to compare the times. The ZX81 is not a very
fast machine, even in FAST mode. Part of the slowness can be
attributed to the fact that the ZX81 stores all numbers as if they
were floating point numbers (ie as if they had digits after a decimal
point), even when they are integers (whole numbers). The more
bytes a variable occupies, the longer it is going to take to process
ZX COMPUTING SUMMER 1962
the information stored, and storing each number as a floating -point
number uses up much more space than does storing such numbers
as integers. Other BASICs (such as the Acorn Atom and the BBC
Microcomputer, for example) allow you to specify which sort of
numbers you wish to deal with, and allots only the necessary space
to do so, thus maximising memory and processing speed. The
ZX80, of course, works only in integers.
Anyway, here is the first benchmark:
1 REM *BENCHMRRK DNE*
5 IF INKEY $**'* THEN GOTO 3
10 IF I N K E Y T H E N GOTO JO
B