Spectrum Prototype

[Spider]

Although the Y.T video has been around for a while now as well as some text here is a more up to date article:

 

http://www.computinghistory.org.uk/det/51620/Sinclair-ZX-Spectrum-Prototype/

 

Now includes ROM image, credit to chop983 over on WOS for the topic itself. Regarding the ROM code, I have not attached it here:

 

 

 

This file is provided for research purposes only and may not be used for any commercial projects.

Special thanks to Kate and John Grant for allowing this file to be made publically available.

© John Grant
Distribution of the file is prohibited.

The Centre for Computing History Ltd
www.ComputingHistory.org.uk

[Spider]

There is a bit of an issue with Ramtop with that ROM image but I did not expect it to behave 100% anyway.

 

Perhaps slightly interestingly if you force the machine into 16K only mode the startup reset enters a loop, unable to deal with that properly. Although again issues were expected this suggests to me that there were immediate plans for the machine to be 48K or more perhaps (up to say the 64K limit 'in one chunk' for the Z80) as otherwise I'd of guessed it would spring into life at 16K.

 

What did surprise me fractionally: I half thought I'd see NineTiles copyright at that stage rather than Sinclair Research. :)

 

 

The prototype pics remind me of the Sam Coupe first prototype, built on a huge breadboard!

[Spider]

Forcing an error to be displayed (use 23610,x) reveals the unused and "not present in released rom" error message , with letter code "S"

 

 

Thought it might be interesting or not to see how it behaves when an IF1 is attached although I suspect there's too much missing for that to work properly, indeed trying to RUN with the microdrive just causes an immediate reset rather than the usual (only happens with an IF1 attached) message of "Program Finished" message with the released ROM... Trying other Mdrive commands usually cause it to freeze.