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Just a few words about the +3ROM:
Note: the +3 ROM, either version, are copyright Amstrad Plc . Amstrad has kindly given it’s permission for it’s copyrighted material to be redistributed, but Amstrad retains it’s copyright.
You should know by now that the original, first released +3, had many problems with the +3BASIC.
Ian Collier has an exhaustive document on this, The Canonical List of +3 Oddities . The document applies to the first +3 release, equipped with ROM v4.0.
Then, there was a the second +3 release, equipped with ROM v4.1. With reference to Ian Collier’s document, I have not checked each flawed address of the ROM v4.1. This is a difficult task, as the new ROM has been reassembled (by Amstrad) and almost all address reference from ROM0 and ROM1 is shifted. However, I checked randomly a few of them and found that some of the “original” bugs are still present. For example (with reference to Ian Collier’s document), the one from address #01D7 and #022F in ROM0. Or address #0769 in ROM1. Or the example 6.
However, there are, for sure, some bug fixes. I am aware of these ones:
But, they introduced a new bug:
If anyone is interested in this ROM version:
The archive contains three ROM size groups – 1×64KiB, 2×32KiB and 4×16KiB – that are suitable either for emulator usage or for physical EPROM writing, where applicable.
I also have the original +3B ROM v4.1 Spanish version. It retains all the bugs and fixes of the v4.1 English version.
Likewise, this one also contains three ROM size groups as mentioned before.
Today I am using a slightly modified version of ROM v4.1.
This ROM is available in two versions, of which one has 4ms head stepper motor timing. If you have replaced your original Amstrad 3” drive with a 720K 3.5” one, or are using two 720K 3.5” disk drives, then using this version will greatly improve the disk access speed under +3DOS environment.
|A new look...
Because of the 50Hz TV screen flicker, the original white background irritate my eyes when working for long time at the +3 in BASIC mode (whereas the blue background less, or not at all)
I have not given any new name to this +3ROM version. The blue background is enough for me to differentiate between two different ROM equipped machines.
This archive also contains the three ROM size groups (i.e 1×64KiB, 2×32KiB and 4×16KiB), but these are further expanded based on stepper motor timing value:
Note: there is only one variable for head stepper motor timing for both drives; it is not possible to have one drive with one timing and the other drive with a different timing.
Important: DO NOT use the ROM with 4 milliseconds stepper motor timing on a +3 that may still use the original Amstrad 3” disk drive !
The timing may also be modified via software (running a program, look at the John Elliot site), however, the software must be then reloaded after each computer reset and it should not be used if the Amstrad 3” disk drive may be in use.
Please note that if the Amstrad 3” disk drive is connected but not in use, the use of 4ms head stepper motor timing has no undesired effect on the 3” drive.
The latest development regarding the +3 ROM can be found on Garry Lancaster’s section at WOS site, The ZX Spectrum +3e . This is an ambitious project, for adding hard disk support to the +3 (or +2A) computers.
As far as I know, the +3e ROM is based on the original ROM v4.0 as supplied with the first +3.