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Re: TS1500 and ZXPand
Posted: Thu Nov 30, 2017 5:10 pm
by sirmorris
L = 8..40k, H = 16-48k. There is always 32K from the 'spand. The 1500 will put RAM at 32-48k so even with M=L there is an overlap. Avoid reading from the overlap areas and everything will be OK
The TS1500 GAL simply turned off RAM above 32k. There is no possibility to swap between modes without a hardware mod.
Re: TS1500 and ZXPand
Posted: Thu Mar 04, 2021 12:37 am
by Slor
sirmorris wrote: ↑Tue Nov 21, 2017 3:26 pm
Nice job!
However I feel I should warn about the fact that both the ZXpand and the TS1500 can simultaneously try to drive the bus when accessing RAM above 32k.
When the '1500 has external memory pulling on its RAMCS line on the edge connector it remaps the internal 16k to sit at 32k. If you start POKEing around nothing bad should come of it because both memory will be reading the bus, but PEEKing will have both ram chips outputting at the same time. If RAM has previously been initialised to some value in that range then both chips will be driving the same value which may be OK. If the RAM is uninitialised then they may drive different values - I don't know what would happen in this case.
Replying to an old thread I know, but hopefully you're still monitoring.
Is there a simple board mod that can be done on the 1500 to prevent the simultaneous drive with bigger memory expansions? Anything that would be easily reversible to get back to stock configuration? If I could simply disable the onboard ram with a cleverly placed jumper, that would be cool and certainly preferable to removing any memory or cutting a trace somewhere. I'm just not smart enough to know if there's an easy solution.
thanks!
Re: TS1500 and ZXPand
Posted: Thu Mar 04, 2021 2:34 pm
by Moggy
Sir morris no longer participates on the forum but for ZXpand queries I believe he monitors Sell My Retro where he sells them and can be contacted there .
Re: TS1500 and ZXPand
Posted: Thu Mar 04, 2021 4:49 pm
by mrtinb
I don’t know if there is a simple way to disable the internal RAM, but you should definitely not disable anything on the ZXpand, because it is this RAM programs are loaded into.