using the incredible compatibility afforded by the front panel headphone jack, i can write a tape from a modern PC and load it into the ZX81

and i run headfirst in to z88dk's limitations, compiling with sccz80 renders in a lethargic 5.4 minutes, sdcc is much faster at 2.5 minutes

but sdcc doesn't seem to support the ZX81 compatible floating point library, so it glitches the video

the inner loop is 16bit fixed point but using it all the way through gets real raunchy precision wise so i thought i'd just use floating point on the outside hahahah

https://www.youtube.com/watch?v=XxWg5hIT2fo

#retrocomputing
#sinclair#ZX81

anyway here's a patched z88dk that cleans up the ZX81 tape output, whoever wrote it clearly wasn't a DSP signals person 😬

https://github.com/SegHaxx/z88dk

makes it all nice and symmetrical, no more DC offset

i'll make it nice sine waves someday

...i was unable to write readable tapes and after driving the SO nuts listening to screeching i determined the super clean outputs on a modern PC cause the vintage cassette recorders aggressive AGC to max out, resulting in mangling the signal when it comes in

the ZX81 has zero error correction and this fails the load

after adding a pilot tone inspired by the Apple II i can write tapes that load 100% reliably and it gives you something to orient on when scrubbing through a tape looking for the start of a file

it also shows as a solid white screen on the ZX81

near as i can tell a real ZX81 is so goddamn RF noisy the video buzz fulfills the same purpose of priming the recorder's AGC

80's tech, man ¯_(ツ)_/¯

...with that i'm kinda burned out on the ZX81 lol

#retrocomputing
#sinclair#ZX81

using the incredible compatibility afforded by the front panel headphone jack, i can write a tape from a modern PC and load it into the ZX81

and i run headfirst in to z88dk's limitations, compiling with sccz80 renders in a lethargic 5.4 minutes, sdcc is much faster at 2.5 minutes

but sdcc doesn't seem to support the ZX81 compatible floating point library, so it glitches the video

the inner loop is 16bit fixed point but using it all the way through gets real raunchy precision wise so i thought i'd just use floating point on the outside hahahah

https://www.youtube.com/watch?v=XxWg5hIT2fo

#retrocomputing
#sinclair#ZX81

i'm way behind on my ZX posting

need some proper mono cables to make the cassette deck go brrr so i grabbed a handful of various vintages from axe man

including this chonky vintage Sony RK-64A cable? sure looks like it came from the 1960s

#retrocomputing
#sinclair#ZX81

Some background on the Sinclair C5, I saw this listed on eBay in the early hours of last Wednesday morning, going through the pictures, it was probably the cheapest complete C5 I have seen, obviously, I bought it

I was lucky enough to be able to go pick it up that very evening, only to discover not only was it complete, it was in fantastic condition; it's current owner got it from new in 1988 for £140 from Comet electrical in Sheffield (original receipt was included in the paperwork), obviously the C5 originally sold for £399 in 1985 and Sinclair Vehicles went bust within 6 months so this was probably a desperate attempt to clear remaining stock, the C5 was developed in Cambridge (completely flat), and with the current owner being in South Yorkshire (VERY hilly), unsurprisingly it saw limited use, before being put in a garage for nearly 40 years until I came along

It was just dirty with a few fairly minimal scratches and some damage to the lower reflective trim (understandable), there was no battery, which is not a problem as it only needs a 12v lead acid battery and the original would be long dead by now anyway, but it did have it's original charger, which is nice even if I'm not sure what I can actually do with it

#sinclair #sinclairc5 #c5#VintageTechnology

Bringing it back to Nottingham Hackspace so I can have a once over at it, 2 out of the 3 tyres were fine, the rear left one needed a new inner tube, thankfully it is just a 16 x 2 inch inner tube that is needed and I was able to get a decent one the next day for £5, but since the wheels are made of plastic, I didn't wanna try and ride it back home from the Hackspace (~1km away) so I had to push it;

That was surprisingly easy, what wasn't however, was when I finally got it home; I had planned on keeping this in a smallish landing area in the entrance to my flat, in a warm dry climate and safe, however it simply was too wide to fit through the door with both the back wheels on/with the door still on it's hinge.

Faced with the prospect of the fact I might have made the most impractical eBay purchase ever, I reluctantly took off one of the wheels and carried it in, before then assaulting my bank account even further with the purchase of a £400 decent bike shed for my back garden, with a plan to purchase an £800 Asgard next pay period to really keep this thing safe, oh well, I was probably going to have to buy something of the sort anyway since my dad keeps pestering me to take my 1960 Excelsior Consort out of his garage

The C5 was safe for now at least

#sinclair #sinclairc5 #c5#VintageTechnology

Some background on the Sinclair C5, I saw this listed on eBay in the early hours of last Wednesday morning, going through the pictures, it was probably the cheapest complete C5 I have seen, obviously, I bought it

I was lucky enough to be able to go pick it up that very evening, only to discover not only was it complete, it was in fantastic condition; it's current owner got it from new in 1988 for £140 from Comet electrical in Sheffield (original receipt was included in the paperwork), obviously the C5 originally sold for £399 in 1985 and Sinclair Vehicles went bust within 6 months so this was probably a desperate attempt to clear remaining stock, the C5 was developed in Cambridge (completely flat), and with the current owner being in South Yorkshire (VERY hilly), unsurprisingly it saw limited use, before being put in a garage for nearly 40 years until I came along

It was just dirty with a few fairly minimal scratches and some damage to the lower reflective trim (understandable), there was no battery, which is not a problem as it only needs a 12v lead acid battery and the original would be long dead by now anyway, but it did have it's original charger, which is nice even if I'm not sure what I can actually do with it

#sinclair #sinclairc5 #c5#VintageTechnology