{"id":1848,"date":"2023-08-02T20:51:31","date_gmt":"2023-08-02T18:51:31","guid":{"rendered":"https:\/\/dlabi.cz\/?p=1848"},"modified":"2026-03-25T18:35:48","modified_gmt":"2026-03-25T17:35:48","slug":"programove-odepinani-monitor-rom-pro-sord-m5","status":"publish","type":"post","link":"https:\/\/dlabi.cz\/en\/programove-odepinani-monitor-rom-pro-sord-m5\/","title":{"rendered":"Software controlled MONITOR ROM deactivation for Sord m5"},"content":{"rendered":"
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The Sord M5 computer has a basic configuration with only 4kB of RAM, which can be expanded to 32kB using an additional cartridge EM-5. By making a small modification to the computer, the memory can be expanded up to 64kB by deactivating of the MONITOR ROM, which occupies the address space 0000-1FFFH. This modification opens up new possibilities for the computer, such as running MSX or ZX Spectrum emulators or CP\/M, and so on. This modification is not something new, it was already realised in the 1980s. The modification itself involves interrupting the connection between pin 15 of the GA15 chip and pin 20 of the IC21 ROM memory , and inserting a resistor with a value between 330-390ohm, as shown in the picture. This weakens the signal from GA15 and allows for external control. The computer's functions remain unchanged by this modification, but various DIY modules, including FlexiCard, can deactivate the MONITOR ROM by setting log. 1 on ROM0 bus signal.<\/p>\n<\/div><\/div>\n\n\n\n

Modification requires you to cut the traces on 2 places and adding one jumper wire depicted on the images below<\/p>\n\n\n\n

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\"\"\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
PCB bottom<\/figcaption><\/figure>\n\n\n\n
\"\"\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
PCB top<\/figcaption><\/figure>\n<\/figure>\n\n\n\n

Disclaimer: Although the modification described here has been tested and is functional, I assume no responsibility for any damage to your device. The GA015 is a custom IC that is nearly impossible to replace, and any damage to it will result in permanent damage to the entire Sord M5.<\/strong><\/p>","protected":false},"excerpt":{"rendered":"

Po\u010d\u00edta\u010d Sord m5 m\u00e1 v z\u00e1kladu pouze 4kB RAM, kterou lze roz\u0161\u00ed\u0159it o 32Kb pomoc\u00ed dodate\u010dn\u00e9ho modulu EM-5. Pomoc\u00ed mal\u00e9 \u00fapravy po\u010d\u00edta\u010de lze v\u0161ak pam\u011b\u0165 roz\u0161\u00ed\u0159it a\u017e na 64kB t\u00edm, \u017ee se odepne MONITOR ROM, kter\u00fd pokr\u00fdv\u00e1 adresov\u00fd prostor 0000-1FFFH. Touto \u00fapravou se otev\u00edraj\u00ed nov\u00e9 mo\u017enosti po\u010d\u00edta\u010de, jako provozov\u00e1n\u00ed emul\u00e1tor\u016f MSX \u010di ZX Spectrum nebo… <\/p>\n

Read More<\/i><\/a><\/div>","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[90,91],"tags":[],"class_list":["post-1848","post","type-post","status-publish","format-standard","hentry","category-schematics","category-sord-m5"],"_links":{"self":[{"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/posts\/1848","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/comments?post=1848"}],"version-history":[{"count":12,"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/posts\/1848\/revisions"}],"predecessor-version":[{"id":3400,"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/posts\/1848\/revisions\/3400"}],"wp:attachment":[{"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/media?parent=1848"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/categories?post=1848"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dlabi.cz\/en\/wp-json\/wp\/v2\/tags?post=1848"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}