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This section is being updated continuously. We are up to Z88 Hardware Investigation. Please return regularly, to see the latest information. |
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Latest NEWS
03/04/17 Having a BREAK from this project.
15/03/17 More tests undertaken in Hardware Investigation
11/03/17 Initial results published
09/03/17 Fernando sent in more results
08/03/17 Fernando sent in his results
07/03/17 Benny sent in more results
28/02/17 Benny sent in his results.
Introduction
Overview
The Z88 software team have been working tirelessly, to bring you the latest and greatest upgrade the Z88 has seen to date, 0Z 4.7.
This version, which uses the RAM intensively, has exposed either a hardware design fault on the board, and/or the specification of the chips used are not fast enough or a software oversight . This affects all versions of OZ 4.x but is only noticeable from OZ 4.6.1 onwards.
It works perfectly on the emulator!
This issue has only affected a handful of user, the majority, who use the normal built-in applications i.e. PipeDream BBCBASIC.
Steps already taken
The fault was initially thought to be due to the decoder on the card. Was it a timing error switching between the RAM and the Flash decode chip? Designing and building Turbocharging the decode chip a faster decoder helped, but did not fully resolve the issue.
We had overlooked that the address line (A19) that selecting them, was not generated by the processor itself, it was generated by a latch. This gave a longer time than expected.
Test Procedure & Results
You are invited to "Send in your results."
This issue is currently being investigated, as some cards work well, whilst others fail.
In the past, these errors have been attributed to
- External card connector being dirty
There is a way to see if the card being used will work before deciding to upgrade or not.a card is affected or not, by doing this test. There is no solution yet, but when there is - it will be published here.
Take part in the testing. See test section.
Information requested
Example
| Z88 OZ 4.x | RAM | RAM | RAM | RAM | FLASH | FLASH | FLASH | ||
| 500000 | Serial Number | ||||||||
| Slot 0 | Slot 1 | Slot 0 | Slot 1 | Slot 2 | Slot 3 | Slot 1 | Slot 2 | Slot 3 | |
|---|---|---|---|---|---|---|---|---|---|
| 512 | SIZE (K) | 32 | 1024 | 1024 | 1024 | ||||
Your Results
| Z88 OZ 4.x | RAM | FLASH | |||||||
| Serial Number | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Slot 0 | Slot 1 | Slot 0 | Slot 1 | Slot 2 | Slot 3 | Slot 1 | Slot 2 | Slot 3 | |
| SIZE (K) | |||||||||
Please send your results direct to vic@rakewell.com so they may be collated and keep checking this page for any updates.
Z88 Hardware Investigation
To discover how the Z88 works it was decided to wire up an external card. Using an oscilloscope and see what the signals are really doing, rather than relying on what Cambridge Computer had documented. See what is happened here.
Use an OTP EPROM
There is a fall-back option which will be tried next. This is using a One Time Program EPROM (mounted in a socket as shown). They are available in 2 sizes:-
- 256K - which could have just OZ 4.7 in it and
- 512K - which could have OZ 4.7 and a 256K file area which could store the zipped version of all the games which could then be run in RAM for example.
This card could also be offered as a 512K/512K EPROM/RAM card as there are no issues using the RAM in the same card.
Conclusion
Jumping to conclusions is not the way to find out what happened before it actually happened. Like us, you'll have to wait.