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OS64 Bug
I recently discovered a latent catastrophe in my OS64 cartridge version 1.72. The cart. sets RAMTOP at 65255. This is ABOVE the machine stack and RAM-resident code. If a long program overwrites the machine stack, it’s BYE-BYE!
The normal place for RAMTOP in double display file modes is 63255, the first byte below UDG. Changing it for double display files was not built into the TS2068 ROM and the OS64 cart. doesn’t do it either.
A “CLEAR 63255” will, of course, reset RAMTOP to the usual and less dangerous address and permit the use of all UDGs. RAMTOP can be raised to 63423 at the expense of the UDGs.
ZXLR8 & ТS1500
Still having trouble with ZXLR8 and the TS1500? Try this: SPEED IT UP! That’s right, try timing values between 7 and 10. This is because the high-pass filter in the TS1500, coupled with the transistor pre-conditioner, can make “1” bits (long pulses) appear as two short pulses. By speeding the routine up (shortening the pulses), this effect is eliminated. With the TS1500, the faster you go, the better it works (subject to the limitations of your recorder). In many cases, this is all it takes; you won’t even need an inverting cable!