Search found 350 matches

by RetroTechie
Mon Feb 20, 2017 10:54 am
Forum: Hardware
Topic: TS1000 ULA vs ZX81 ULA
Replies: 24
Views: 2212

Re: TS1000 ULA vs ZX81 ULA

ULA pin 22. Has an internal pull-up. Optionally pulled low by (external) resistor R30. Pin readable as bit 6 of I/O port FEh. The ZX81 ROM uses this bit to set system variable MARGIN (address 16424), which holds the number of blank lines in the top & bottom border. With the ULA pin low (R30 present)...
by RetroTechie
Mon Feb 20, 2017 12:28 am
Forum: ZX Spectrum Lounge
Topic: ZX Spectrum Next
Replies: 31
Views: 7016

Re: ZX Spectrum Next

From what I've read, the Spectrum Next is FPGA based (their site mentions Altera Cyclone II) and designed to be open / hacker-friendly. I tend to judge FPGA boards on the FPGA used (family, # of LE's, # of IO's accessible etc), integrated peripherals, documentation, and ready-to-use softcores availa...
by RetroTechie
Thu Feb 16, 2017 5:55 am
Forum: Hardware
Topic: ZX81 PSU?
Replies: 8
Views: 844

Re: ZX81 PSU?

msansom wrote:It's a 3.5mm mono phone jack and I think that the + is on the tip.
Confirmed - 100% certain. Original ZX81 PSU is center pin positive (+).

EDIT: Paul wrote faster... :mrgreen:
by RetroTechie
Fri Feb 10, 2017 9:10 pm
Forum: Sinclair Misc
Topic: The Future of Sinclair ZX World
Replies: 57
Views: 8351

Re: The Future of Sinclair ZX World

Taking account of my ongoing health issues (..) Sorry to hear that, Rich. :( If you had just a simple not for profit organisation that wasn't a limited company, then the hosting and domain names would have to be in the name of one person, who might not be with the organisation after a while and the...
by RetroTechie
Tue Feb 07, 2017 6:28 pm
Forum: Hardware
Topic: "Different" ZX81's
Replies: 190
Views: 17816

Re: "Different" ZX81's

Moggy wrote:LOTS OF DOORS IN YOUR HOUSE!!?

Blasphemy burn him with fire I say. :evil:
But you need spares! In case your, ehm... doors break down or something. :lol:
(5 here, one of which in Dk'tronics kb)
by RetroTechie
Tue Feb 07, 2017 4:54 pm
Forum: GAMES
Topic: Sorting out some things......
Replies: 5
Views: 1026

Re: Sorting out some things......

For machines like the ZX81, I think it's good practice to ALWAYS test on real hardware before doing a release. Kind of a standard quality control 'checkbox item'. But given how good some emulators are, I can understand how tempting it is to skip that step ;) (which tbh can be a hassle depending on y...
by RetroTechie
Sat Feb 04, 2017 6:39 pm
Forum: Hardware
Topic: Putting a ZX81 onto a CPLD
Replies: 59
Views: 5901

Re: Putting a ZX81 onto a CPLD

I suspect mdave4953 means programmable logic devices (PAL/GAL/CPLD/...) in general. CPLD's are probably the most practical / cost-effective these days. Wish new users would check the archives before asking: Hardware -> ZX81 ULA replacement revisited Hardware -> List of ULA availability among similar...
by RetroTechie
Sun Jan 29, 2017 2:09 pm
Forum: Hardware
Topic: "Different" ZX81's
Replies: 190
Views: 17816

Re: "Different" ZX81's

This (short!) Wikipedia article explains it all: Zetex Semiconductors Logo found on this Tweakers.net electronics-related page: Manufacturers of ICs and their logos Must say, one bl**dy hard to find logo when it comes to IC manufacturers! :shock: (and I've seen quite a few in my life :mrgreen: )
by RetroTechie
Sun Jan 22, 2017 10:45 pm
Forum: Hardware
Topic: Sparkly pixels
Replies: 65
Views: 6268

Re: Sparkly pixels

@Moggy: you're looking at the wrong end.. that's not a cooling solution, but a HEATING solution! :lol: The ONLY point I am trying to get across is that in an enclosed unventilated system heat sinks serve little purpose without a through put of air like a PC for example. Still it's useful. Thermals a...
by RetroTechie
Wed Jan 18, 2017 12:44 am
Forum: Hardware
Topic: MicroPath P1
Replies: 5
Views: 816

Re: MicroPath P1

I suppose this is one of those custom applications with low # of users which must have been fairly common for the ZX81. Just not many surviving beyond their intended use. :( A ROM add-on + matching sticker over the keyboard, not that special from a technical p.o.v. really. Nice find though! Curved p...