External memory upgrade for ZX16/48

[VELESOFT]

See here:
http://www.worldofspectrum.org/forum...ad.php?t=33611

[Advertiser]

[goodboy]

+ paging port #7FFD at 90% compatible with ZX128 / Pentagon 128,512,1MB

- paging port #7FFD can't select second videoram, only first videoram is used.
- ram page 5 is not mirrored with first videoram (16384-32767), it's only classic ram page

[VELESOFT]

+ paging port #7FFD at 90% compatible with ZX128 / Pentagon 128,512,1MB

- paging port #7FFD can't select second videoram, only first videoram is used.
- ram page 5 is not mirrored with first videoram (16384-32767), it's only classic ram page

Not all is true. You read only old info on WOS. This is actual version compatibility:

Paging port 7FFD is 100% compatible as ZX128. Port adressation is A15=0, A1=0, IORQ=0, WR=0

Ram page 5 are mirrored with area 16384-32767. If you write data to memory area 16384-32767 then same data are readable from page 5 in high memory 49152-65535. If you write data to page 5 in adress 49152-65535 then same values will readable from 16384-32767, but this writing not write data to real videoram chips.

Memory mirroring in pages 2 and 5 are 100% compatible with ZX128, only writing to page 5 in high memory 49152-65535 can't change graphic data in physical videoram 1. Software work correct, CPU see correct data, only on TV output can be graphic data different if software use mirroring to page 5.

External memory upgrade for 16/48kB ZX computers can't show second videoram and can't mirror data writing from 49152-65535 to 16384-32767.

[Black_Cat]

goodboy, невозможно отобразить на экране только 7 страницу, и только для ZX48. Т.е. не будет работать Gigascreen, и всё, что использует 7 страницу для видеовывода. У тебя что, 48 Спек?