Hardware and Firmware Errors and Bugs

[1024MAK]

Hardware and Firmware Errors and Bugs

Now, it is not difficult to find details of the hardware limitations and ROM bugs for both the Sinclair ZX Spectrum and the Sinclair QL.
If you know where to look, there are also details of some of Acorn's bugs in the Beeb OS (or MOS as they latter named it) and in 6502 BBC BASIC. The Spectrum, the QL and the BBC A & B machines all had little hardware design problems, all of which required mods in the early versions of the machines.

However, there is not much information floating about the web about such problems with Memotech MTX machines.
Yes, some boards have Memotech yellow wiring, but most of this is due to expanding what the PCB could do compared to the original design. Memotech using different ROMs/PROMs or EPROMs also results in some yellow wiring.

So do you know of any hardware problems with Memotech MTX kit?

Have you discovered any bugs in any MTX ROMs?

Do spill the beans...

Mark

[Dave]

Possible candidates . . . .

1. Screen position - offset to the left by 1 character or so

2. Circles drawn as ovals (aspect ratio related)

regards
Dave

[Bill B]

The BASIC ROM includes an undocumented function FREE(). I guess that it was intended to return the amount of free memory, but in practice it just duplicates one of the other functions (EXP if memory serves me). Lack of space in the ROM for the extra code?

[Crazyboss]

Yes the Free function is not very usefull.

I dont know if its bugs, but the Circle command draw the circle as it should, but because you have 255 x 191 dots it dont look totaly round, The MSX does the same, but at MSX they did it more clever by only calculate 25% or less of the drawing and mirror them

Some weird things is when you use CSR (locate) command, its X,Y - and 0,0 is up left corner, but when using pixels like Plot 0,0 is lower left corner.

But its also weird on Qbasic (MAYBE gw basic and so) the Locate command is Y,X

DIM a(0) is not allowed. first array is 1

Sprites can go outside the 255x191 area, but pixels are not allowed outside.

Error messages from The Memotech Basic is quite weird too. Error messages like A, SE.C and so

IF you edit a basic line which is a DATA line, then it move the first data one space left every time

LET command must be used And all variables must be declared

What is good about the Memotech Basic editor is, it removes spaces which are not used and make the code look good.

According to Andy Key there was only the same basic rom same maybe for other roms. So they didn find (or correct) any errors.

People think Verify had a bug, but in fact not. When you save a program like: SAVE "MY PROGRAM" and later used VERIFY"" you got a mismatch error - ofcause cause the name you saved had a different name than "" so when using VERIFY use the same name as for SAVE. Remember if you dont want to save variables use CLEAR before SAVE.


Hacks ? you can eg POKE 64863,54 to turbo save programs in basic.

[thewiz]

Wow! Thats some list Crazyboss.

Its been a long time since I used the MTX full time (about 30 years ) but I did notice that it takes a couple of seconds after bootup for the cursor to start flashing.

Paul

[Martin A]

Wow! Thats some list Crazyboss.

Its been a long time since I used the MTX full time (about 30 years ) but I did notice that it takes a couple of seconds after bootup for the cursor to start flashing.

Paul

I think I found the answer to that when I was investigating the startup sequence for Magrom. It would appear that the cursor flash counter isn't set on reset, so the counter counts down from 0 (ie 256) until it reaches 0 again, and then the counter gets reset to the correct flash value

[AndyKey]

SDX ROM for type B:07,C:07 drives has bug in check and allocation vectors (insufficient space for them, so they overlap).
Without this fixed, I can't save anything - BDOS Err R/O.

In FDXB, you need to DISC DIR "" before DISC SAVE to avoid disk corruption.

FDXB has numerous other bugs/limitations relating to the fact it replaces rather than sits on top of CP/M.
eg: only supports certain drive types.
eg: assumes B: and C: are the same drive type

[AndyKey]

MTX500 address decoder PAL makes some of the 32KB memory appear in extra unwanted places in the memory map.

This clashes with where memory upgrades (eg: official RAM upgrade board, MTX Memory Card, REMEMOrizer) make the extra memory appear.

So prior to upgrading memory on an MTX500, this PAL has to be replaced.
Suitable PALASM is in the file 2_32.eqn or 3_32.eqn on my website.

This is why I ship a GAL to replace the PAL when I ship a REMEMOrizer to a customer with a MTX500.

[AndyKey]

The address mapper bipolar PROM in my one-off special SDX had a page mapping mismatch.

Either, this is a one-off mistake in just this machine.

Or, there could be others, perhaps Memotech Business/2 machines, with the same problem.


If there are, no problem, my "SDX Plus" upgrade can address this for £6.

[AndyKey]

I forget the details, but I think the card in the FDX with the boot ROM and ribbon connector doesn't address the ROM properly.

We should be able to put 2 8KB images (ROM 4 and 5) in a 16KB chip.

Instead of decoding R0 to pick the lower or upper 8KB it decodes an address bus signal.


I think fixing this is possible on Clauses machine with a track cut and a yellow wire.
His "FDXB single" could be both boot CP/M and have SDX ROM support.