{"id":7626,"date":"2025-10-30T15:45:01","date_gmt":"2025-10-30T20:45:01","guid":{"rendered":"https:\/\/pugix.com\/synth\/?p=7626"},"modified":"2025-10-30T15:45:03","modified_gmt":"2025-10-30T20:45:03","slug":"something-i-did-43-years-ago","status":"publish","type":"post","link":"https:\/\/pugix.com\/synth\/something-i-did-43-years-ago\/","title":{"rendered":"Something I did 43 years ago"},"content":{"rendered":"\n
\"\"
Hunter RAM board<\/figcaption><\/figure>\n\n\n\n

I learned to program the Z80 microprocessor in Z80 assembly language by building a Timex\/Sinclair ZX-81 kit and adding memory to it. Pictured above is a Hunter static<\/strong> RAM board that could store 4K of data over power cycling. I added a battery as suggested in the manual, with a switch to enable it before turning off the ZX-81.<\/p>\n\n\n\n

\"\"
Hunter RAM board bottom<\/figcaption><\/figure>\n\n\n\n
\"\"
Hunter RAM board instructions<\/figcaption><\/figure>\n\n\n\n
\"\"
Hunter RAM board schematic<\/figcaption><\/figure>\n\n\n\n

Byte-Back M-16 16K Dynamic Ram<\/h3>\n\n\n\n

The ZX-81 came with a measly 2K of RAM. Even so, it was enough to write simple programs in the built-in BASIC language. For assembly language programming more RAM was needed. I built two Byte-Back M-16 memory board kits. One was more heavily modified.<\/p>\n\n\n\n

\"\"
Byte-Back M-16 #1<\/figcaption><\/figure>\n\n\n\n

The toggle switch allowed the 16K to be placed in different blocks of the 64K total memory space.<\/p>\n\n\n\n

\"\"
Byte-Back M-16 #1 back side<\/figcaption><\/figure>\n\n\n\n

Number 1 had and extension edge connector for adding a second accessory.<\/p>\n\n\n\n

\"\"
Byte-Back M-16 #2<\/figcaption><\/figure>\n\n\n\n
\"\"
Byte-Back M-16 #2 back side<\/figcaption><\/figure>\n\n\n\n

After 40 years, there’s quite a bit of corrosion from the no-clean 60\/40 solder I used.<\/p>\n\n\n\n

\"\"
M-16 Manual<\/figcaption><\/figure>\n\n\n\n
\"\"
M-16 schematic, showing some modifications<\/figcaption><\/figure>\n\n\n\n
\"\"
My first ZX-81 had a reset switch added<\/figcaption><\/figure>\n\n\n\n

The cheat sheet has memory locations used during assembly language programming.<\/p>\n\n\n\n

\"\"
A huge ZX-81 bundle that’s going up for sale<\/figcaption><\/figure>\n\n\n\n

I hear there are still computer geeks building and programing the ZX-81 microcomputer. It was a great way to learn Z80 assembly language.<\/p>\n","protected":false},"excerpt":{"rendered":"

I learned to program the Z80 microprocessor in Z80 assembly language by building a Timex\/Sinclair ZX-81 kit and adding memory to it. Pictured above is a Hunter static RAM board … Read More<\/a><\/p>\n","protected":false},"author":1,"featured_media":7637,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[125],"tags":[71],"class_list":["post-7626","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-musings","tag-diy"],"yoast_head":"\nSomething I did 43 years ago - Richard Brewster's Electronic Sounds<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/pugix.com\/synth\/something-i-did-43-years-ago\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Something I did 43 years ago - Richard Brewster's Electronic Sounds\" \/>\n<meta property=\"og:description\" content=\"I learned to program the Z80 microprocessor in Z80 assembly language by building a Timex\/Sinclair ZX-81 kit and adding memory to it. 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