Sinclair ZX80 / ZX81 / Z88 Forums

good to know. i write these out so i can remember and it's only partially working

TOOLKIT (written by PAUL HOLMES) A Solid Programmer's Toolkit : JRS software toolkit Version: 16k (1982) and they are not kidding. The machine will crash if the loading instructions are not followed Toolkit by Paul Holmes, sold by JRS Software (UK) for 4.95. Available from 1981, it is a very early ...

thanks, i had a typo. i meant to write that 622 had the PAUSE bug, and 649 fixed all the bugs

to recap:
555 is the "unimproved" ROM
622 and 649 are the "improved" ROMs

550 is the original ROM (the "unimproved" ROM), and it had several major bugs 622 is the "improved" ROM, which fixed those. However, 622 introduced a minor bug, which was then fixed in 649. As I understand it, 622 is the most infrequently found version as it was updated quickly on the production lin...

After having my interest piqued by the Interface magazine thread , i've been digging into JRS advertisement seen on page 20 Dunno how good these games were but the advertising copy text is superb! Interface 1982 February page 20 advert.jpg ZX80 JRS SOFTWARE ZX81 19 WAYSIDE AVENUE, WORTHING, SUSSEX, ...

Second article To use machine code (MC) in the above-32K RAM area requires two things: Modify the BYTE-BACK M-64/UM-64 memory pack Modify your ZX81 for M1 NOT Decoding per John Oliger's article The UM-64 had an EEPROM socket and battery backup, in addition to the 64K dynamic RAM. Both M-64 and UM-64...

Thanks

I found this earlier article by John Oliger which outlined how to modify a ZX81 to use more memory than 16K. It uses a quad NAND gate IC chip (74LS00) to decode the chip select for an extra 16K (for example, when using two 16K RAM packs) "M1NOT" is not explicitly stated, but for the 3rd 16K block it...

mrtinb wrote: ↑Wed Nov 16, 2022 7:30 pm Andy Rea's ULA has a jumper to enable/disable M1NOT.

So is "M1NOT" the same as the John Oliger machine code circuit modification? I think so as Jeffrey D. Moore calls it "Oliger's NOT Ml decoding circuit"

This circuit will allow you to use the 32-48K RAM area for machine code, with RAM packs such as the Memotech Memopak 64 or JLO 64K , but not the Byte-Back UM. From SyncWare News Volume 2 no. 5 May-June 1985 page 10 HARDWARE PROJECTS Run TS1000 Machine Code in High Memory John Oliger ZX81ers don't de...