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IN MAV’S WORKSHOP
by Ian Mavric
Part 4 of the HARD DRIVE Trilogy
HARD DRIVES AND THE TRS-80 MODEL I
Last time1 I concluded my trilogy of hard drive articles for
the Model III and 4. I focussed on the Model III and 4
since 99% of hard drives sold to the 8-bit Z80 systems were
used on those computers. In fact not many people know that
a hard drive could be even connected to a Model I.
Obviously I own one, I use it a few times a week, and I was
part of the team who helped make the FreHD2 hard drive
emulator work with the Model I, so I think I know a bit
about them.
HISTORY
In 1977 when Tandy designed and built the first few machines
with Level I BASIC and 250 baud cassette storage they could
hardly have imagined that only 5 or 6 years later Winchester
hard disk storage, similar to that available on minicomputers, was going to be affordable and store megabytes of
data. When you are designing a 4K microcomputer 5 megabytes
must have sounded like a miracle. When Tandy went back to
the drawing board to design the Model III, it was clear that
the large 50-way I/O bus was designed around connecting a
hard drive. The Model III hit the showrooms in 1980 and the
hard drive in late 1982 as our old favourite 5 Meg Disk
System 26-1130 in RSC-8 Sept 1982.
Something as expensive as a hard disk drive normally needs a
killer-app in order to hook in potential buyers and in the
case of the Model III it was Profile III Plus HD, and early
database management system that was fast and with a hard
drive, capable of building enormous databases. There was no
such app for the Model I and since the computer had been
forced into retirement in 1980 by the FCC, Tandy could
probably have overlooked making the hard drive work with
the Model I and not many people would have cared. This is
where you see the clever minds at work at Radio Shack
pulling yet another trick out of their hat for Model I
owners. A small adapter kit called, blandly enough, the
"Model I Hard Disk Adapter Kit" (26-1132) was sold for only
$70 (see below). Once you own the hard disk, you are kind
of locked-into the TRS-80 product for the next few years.
It is no co-incidence that 5Mb hard drive works perfectly on
the soon-to-be-released Model 4. So what if the owner had a
lot of money invested in their Model I, and didn't feel like
TRS8BIT
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volume 07 Issue 04 - December 2013
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page 24