OK, so that theory goes out of the window.
I may have to get the other machine down from the loft and test with the other CFX card to make sure that it's not the device.
Search found 326 matches
- 16 May 2019 12:55
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
- 16 May 2019 10:10
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
Re: Resurrecting an MTX500.
I've been thinking (that's a dangerous concept in itself), as BASIC is rock solid on the machine and I can't get any memory test to fail at all whether the issue with the CTX is to do with the generation of the /GROM signal. If this is inconsistent could this cause the external ROM based programs to...
- 15 May 2019 23:26
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
Re: Resurrecting an MTX500.
As suspected "-1.0" gets changed from a floating point to an integer.
- 15 May 2019 17:57
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
Re: Resurrecting an MTX500.
You might find this interesting http://primrosebank.net/computers/mtx/techlib/mtx/mtx_basic_vars.htm Indeed, interesting. I'd still need to decode the address in assembler. That document also hints that the numeric format for the MTX is indeed the same as the ZX81 & ZX Spectrum, being five byte...
- 15 May 2019 17:33
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
Re: Resurrecting an MTX500.
Hmmm.. I wonder if I can find the address of the start of the array. I hate accessing unallocated memory. Blame my system programming background.
- 15 May 2019 12:04
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
Re: Resurrecting an MTX500.
As far as I can remember MTX BASIC doesn't have a true integer type so numeric arrays will allocate memory large enough for any sized value. So, to test the memory allocated in the array you need to assign values which set/unset every bit in that storage class. As for 1010101010 etc. unless you have...
- 15 May 2019 10:22
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
Re: Resurrecting an MTX500.
If you want to confirm if the DRAM is being refreshed, limit the CPU to a short loop for at least 20ms. Then check the contents of memory. Mark It looks like I'm going to have to learn how to use the MTX assembler doesn't it? :-) The first test may be swapping the CPU as I have at least one unused ...
- 15 May 2019 10:15
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
- 14 May 2019 23:25
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
Re: Resurrecting an MTX500.
I wonder if there might be a problem with the DRAM timing circuit? Assuming that all the chips in the circuit are working, it might be worth checking C5 and C6 for damage. With all the work on the machine, they might have taken a knock? I had a weird RAM fault that turned out to be a cracked capaci...
- 14 May 2019 22:38
- Forum: HARDWARE
- Topic: Resurrecting an MTX500.
- Replies: 226
- Views: 177674
Re: Resurrecting an MTX500.
Having replaced the two LS273s and used switch cleaner/lubricant plus a bit of key tapping I have a working keyboard. It's not perfect as I get double characters on some keys now and again but it's usable. I also replaced the three LS244 chips as I no-longer trust them as they've been through a lot ...