Sinclair +2a Why!?!
One thing I've always wondered and whilst going though my collection today the question re-emerged in my mind. Why the Spectrum +2a?
What I mean by this is why did Amstrad re-design the +2 to provide it with only a printer interface and a much more complex power supply. I understand why this was needed in the +3, but why go to the expense of re-tooling and redesign for something that is effectively the same machine?
What I mean by this is why did Amstrad re-design the +2 to provide it with only a printer interface and a much more complex power supply. I understand why this was needed in the +3, but why go to the expense of re-tooling and redesign for something that is effectively the same machine?
Post edited by Scottie_uk on
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Comments
The +2 was a complicated machine with lots of components. Spinning an ASIC for the +3 but keeping buying in ULAs for the +2 would have made no sense.
Really, anyone who wanted to use disks would just have bought the +3 anyway you'd think. Amstrad probably decided they wouldn't sell enough interfaces to make it worth the cost of tooling up.
Threw my 3" drive away last year popped a 3.5 in instead, got a ready made adaptor cable from Ebay just left the 'tidyness' of the drive mounting really, its OK but I'm still not 100% happy with it. Another day maybe. :)
No, it won't work (in most cases).
There were two kinds of external CPC drives. One of them allowed "tape" CPCs to use disks (Amstrad DDI-1), and the other was a second drive for "disk" CPCs (Amstrad FD-1).
Also there were two kinds of Spectrum +2A, one kind (re)used +3 boards but without disk controller chips and the other used cut-down (literally) cost boards.
The Amstrad DDI-1 is useless for Spectrums. The Amstrad FD-1 would work as a second drive for +3, or (slightly modified) as a drive for +2A computers after installing the missing chips. Note that if you've got a "cut-down" +2A board, you've got no external floppy connector and you won't be able to connect the FD-1.
But... there is a floppy interface (really a copy of internal +3 interface) that would allow to convert a +2A into a +3 (and then connect one of those FD-1).
An' you know what they said?
Well, some of it was true!
The +2A case blocks off the drive B connector, but even if you removed the board it wouldn't work because the floppy controller and data separator are missing. The +2B did away with the circuitry and the connector completely of course.
To use a floppy drive with the +2A or +2B would require the Amstrad SI-1 (or a homemade "clone" [1]). This would be an external copy of the disk controller circuits which are internal on the +3.
[1] can you clone a device which doesn't exist [2], there must be a better word for that.
[2] well, probably. As you know, I'm happy to re-evaluate my position on whether things exist or not, just as soon as I have photographic evidence [3] of them
[3] Convincing photographic evidence I mean, not an out of focus snap that could be a bit of driftwood or a man in a monkey suit ;)
Note that that circuit is somewhat overcomplicated by implementing the data separator from scratch.
If you can get hold of the SED9420 then you wouldn't need to find the (also rare!) BPROM
schombi.de/my-retro-collection.html"
The DDI-1 is actually just the disc controller interface (and AMSDOS ROM) for a tape-based CPC, the actual drive itself was always an FD-1 (DDI = Disc Drive Interface, FD = Floppy Drive).