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The ZX Spectrum was announced with support for both standard cassette tapes and Sinclair's new Microdrive format -- although the latter wasn't released for another 17 months.

Given that the necessary hardware to use the Microdrive -- Interface 1 and the drive itself -- weren't built into the Spectrum, it could be assumed that Sinclair saw it as a secondary feature.

Admittedly a tape player wasn't built in either, but many homes would already have one of these available.

My question is, is there any evidence that Sinclair intended for the Microdrive to be the primary storage media moving forward for their hardware, and that the botched execution -- consumers having to buy additional hardware -- was just naivety on Sinclair's part?

Or was the intention for the cassette and Microdrive to live side by side over the long term?

Given that the Microdrive was built into the QL as standard, I've assumed that the Spectrum implementation of the Microdrive was just a transitional phase.

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    That Question seems to replace basic consideration by unguided speculation. Or was the Floppy also considered a secondary Medium for the IBM-C, just because it was delivered with a cassette port? Or the Apple II, or any other computer with a cassette port build in and the ability to have am interface for a different/better storage added later?
    – Raffzahn
    May 13, 2022 at 11:25
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    Pricing. IIRC the basic 16k Spectrum could be bought for just under £100. Once you've sold the base unit people will happily buy add-ons to improve their system.
    – user24174
    May 13, 2022 at 11:37
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    Pricing and time-to-market. That 17 months that it took to refine the microdrive to customer-readiness was time while Spectrum sales were supporting the R&D.
    – Toby Speight
    May 13, 2022 at 12:53
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    @TobySpeight - as a former QL microdrive user, your comment about "refin[ing] the microdrive to customer-readiness" was absolutely hilarious
    – scruss
    May 13, 2022 at 19:48
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    There seems to be an assumption in this question that that the Microdrive hardware was ready and could have been built into the Spectrum at the Spectrum's release. But that seems belied by that even as a stand-alone item the Microdrive wasn't available for another year and a half. Further, as pointed out by others, there were many other systems that did not include a drive as standard, especially at the start; the one perhaps closest to the Spectrum is the Commodore 64.
    – cjs
    May 25, 2022 at 7:53

3 Answers 3

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I think the story of the Sinclair Microdrive fits nicely with similar stories of other data tape drives offered at the same time.

In the early 1980's, there was at least the Sinclair Microdrive, Coleco Adam with its "Data Pack" cassettes, and Exatron's "Stringy Floppy" for multiple systems. These were independent, proprietary, efforts by (relatively) small manufacturers to offer a lower-cost alternative to floppy disks and drives - That was the intent.

All of these alternatives struggled in the market to gain any traction. Frankly, the market chose 5.25" floppy media and drives instead of these tape-based solutions. And, as floppies gained traction in the market, the cost of floppy media and drives fell precipitously.

These improvements in floppy price and availability eroded most, if not all, of the "value proposition" of these proprietary tape alternatives. Neither users, nor 3rd-party software publishers, provided enough uptake for these storage media to have much of a life. It became just another technology "detour" that the market rejected. Who could have known?

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    The other issue, is simply that the floppy drive offered a magnitude more functionality. Efficient random access was a complete game changer in terms of functionality. It was no longer "load" "do work" "store", but now you can store as you go, make efficient copies, etc. The "stringy floppy" style of media were very nice for accessing multiple files on a single piece of media, but as soon as you started writing to them, it all went down hill. The floppy was simply a much better device all around.
    – Will Hartung
    May 13, 2022 at 15:15
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    @WillHartung Right, you are. It seems "the market" was choosing wisely.
    – Brian H
    May 13, 2022 at 15:17
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    @WillHartung: If a tape held four programs that each took a quarter of the tape, and could seek four times as fast it could read or write data, then the worst-case time to find and load a program from tape would be only twice as long as it would be if the seeking was instantaneous. In the early 8-bit era, a logic controlled cassette deck could be had cheaper than a floppy drive, so adapting one for computer use would make sense. The cost to produce floppy drives on a comparable scale, however, was lower than the cost to produce logic-controlled cassette decks.
    – supercat
    May 13, 2022 at 16:54
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    Do bear in mind that at that date many mainframe systems processed from master tape + updates -> new master, so using a cassette or microdrive was not that different. Indeed, as late as 1980 DEC were incorporating the block addressable TU58 tape in the 11/750 as a cheaper alternative to the 8" floppy in the 11/780.
    – user24174
    May 13, 2022 at 19:06
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    Floppy drives and disks remained expensive in the UK for quite a while, originally because of import tariffs. For example, using Watford Electronics (in The Micro User magazine), their SS/SD cased drive with cable and PSU was £188 in June 1983 but £119 in March 1985 (US $291, $134) . A box of SS/SD floppies was £20 in 1983 but £14 in 1985 (US $31, ~$16; forex source FRED, rate cratered over this period)
    – scruss
    May 13, 2022 at 20:20
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That product decision was very probably driven in a big part by Sinclair's (both the company and the man himself) fascination for aggressively simplified technical solutions and shifting the task from expensive hardware to cheap software solutions. Following that principle, the company had achieved to come up with the first $100 "usable" computer and its descendant and megaseller, the ZX Spectrum. So, that approach was apparently working.

The very same principle was applied to try and solve the problem of the storage medium for the ZX Spectrum and planned later Sinclair computers (the QL): On the one hand, there was the cheap, but quirky to handle cassette tape, on the other hand, the elegant, but expensive random access possible with floppy drives - Sinclair apparently wanted something in-between and built it. They used relatively modern ULA chip technology to handle the direct-to-tape and sector locating logic and miniaturized the tapes and drives (I don't know of any evidence that Sinclair engineers were looking at, or even inspired by the Exatron Stringy Floppy, but it's likely).

The approach had, however, two major flaws: Mastering the technical challenges took too long while floppy drives and their media became cheaper and cheaper through volume uptake, and the cost of the media itself (while its storage capacity/cartridge could maybe be tolerated at least in an 8-bit computer) was already far from competitive with floppy disks. The storage capacity on the QL - with 100kBytes/cartridge on a computer that could be expanded to 640k of memory - was not really adequate.

By the time the Microdrives were somewhat "ready", third-party single floppy drives from Japan were reportedly already cheaper to have in quantity than the self-developed two-drive Microdrive system, but Sinclair (the person) stubbornly followed that path and nobody in the company dared to steer around or even tell him (Allegedly, there were secret contact attempts between Sinclair engineering staff and Japanese drive manufacturers that were hidden from Clive Sinclair). The QL might have turned out to be a totally different computer with a single floppy drive.

As I've already written elsewhere, the Microdrive reliability was much better than purported, at least after the system was fixed through a number of relative costly factory upgrades: I have some cartridges and drives for my QL that have survived nearly forty years of usage and are still doing great.

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    The "aggressively simplified technical solutions and shifting the task from expensive hardware to cheap software solutions" could have been applied to a floppy diskette system, as well. And in fact it had been, many years earlier, by Wozniak at Apple. There not even a ULA was necessary; the entire controller was a ROM and few 7400-series parts talking to a Shugart drive with stripped down electronics.
    – cjs
    May 25, 2022 at 7:52
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    @hippietrail More seriously, comparing 1983 prices, £80 was about US$125. The 1983-06 Byte has at least two adverts (pp.533, 540) offering an Apple II drive and controller for about $290. So yeah, still more than twice the price at the point of the Microdrive's release. But I'm willing to be that Sinclair could have gotten the costs down even further: at that point the Apple-compatible drives were about 15% more expensive than the cheapest PC drives, despite PC drives being double- (rather than single-) sided and having a more expensive analog/control board.
    – cjs
    May 25, 2022 at 14:03
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    @cjs On the QL, the Microdrives aren't really significantly slower than floppies - With its clever slave block mechanism and multitasking OS, all the free memory is used as buffers, and a complete cartridge can be read in ~7 seconds. On a fully expanded machine, you're basically working on a RAM disk that is automatically streamed back to tape in the background (which is again a sign of the ridiculously small capacity of the cartridges for such a computer)
    – tofro
    May 25, 2022 at 17:42
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    @tofo That's quite interesting, though of course it applies only to the QL, not the Spectrum, and is really at that point a random access comparison. (I compared sequential access on the assumption that loading programs was a common enough application that one would want to compare that. Looking at it again, though, I think I was off on my estimates of sequential read speed: best case Microdrive is almost the same speed as floppies and it worst it's still probably about half the speed. I overestimated floppies, which even on PCs were under 25 kb/sec.)
    – cjs
    May 25, 2022 at 20:41
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    @cjs I'm pretty sure that more than 50% of the Microdrive's bad reputation is just hearsay, repeated from real problems in the initial phase over and over again. Once Sinclair got them stabilized, they worked pretty flawlessly, if handled correctly. Another angle for lack of trust in the technology is the sound they make wen crunching through the tape - They definitely don't sound very trustworthy. But, then again, the Apple II's headbanging initialization sequence doesn't sound very convincing either, but these are really reliable disk systems.
    – tofro
    May 26, 2022 at 12:53
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Given that the necessary hardware to use the Microdrive -- Interface 1 and the drive itself -- weren't built into the Spectrum, it could be assumed that Sinclair saw it as a secondary feature.

That's an unwarranted assumption. The UK home computer market at the time was extremely competitive, with new ideas appearing frequently. The Spectrum had to be cheap, and it had to be launched quickly.

That meant that adding the mechanism of a Microdrive to the machine was ruled out on the grounds of cost, and because they weren't ready when the Spectrum launched. Delaying the launch of the Spectrum until Microdrives were available and cheap would have involved a huge risk of Sinclair Research going bust; the ZX81 was obsolete and its declining sales could not have sustained the company.

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