[cctalk] Re: 8P8C but width of an RJ-11
>Patch cords…for banjos?? A postscript to my previous reply While 'Mean' Mary James doesn't typically use one, Deering Banjo does have an acoustic-electric banjo: https://www.deeringbanjos.com/products/deering-sierra-5-string-acoustic-electric-banjo And Led Zeppelin joins other rock bands to use the banjo in 'Gallows Pole' - even Less Claypool goes 'bassjo' in Primus' 'The Air is Getting Slippery.'
[cctalk] Re: 8P8C but width of an RJ-11
>Patch cords…for banjos?? A 'banjo' in this context is a device that breaks out the conductors of a modular jack to test points. Older ones were round-ish and had a hardwired short flat cord (usually 'silver satin' flat cable) with a modular plug on the end l. Sandman carries an 8 conductor banjo with a short patch cord with two of these universal plugs on it; https://sandman.com/products/too6g-modular-2-4-6-8-pin-butt-set-banjo-adapter Having said that, there are pickups available for the musical instrument banjo..but that's not this banjo.
[cctalk] Re: 8P8C but width of an RJ-11
>Subject: [cctalk] 8P8C but width of an RJ-11 >It's 8P8C with a little offset snag >reminiscent of a DEC MMJ, but it's the width of an RJ-11: while an >"RJ-45" >Ethernet cable is too wide, a phone handset cord is the right width >even >though >it obviously doesn't have enough connectors. I messed around with >filing down >a >junk Ethernet patch cord but that's just making a mess bigger than >the icky >cable. >I think this is a standard connector, but I'm not sure which? Sandman Electronics carries what they call a 'universal' modular plug, 8P8C but the width of a 6P6C or 4P4C (RJ11). You can look at it at https://sandman.com/products/too5o-blue-universal-mod-plug and they're used for patch cords for banjos, like used with clip lead butt sets. This way you can have one 8 connection banjo with 8P8C jacks but use it with both the wide 8P and medium 6/4P jacks (of course NOT the narrow headset 4P jacks). Sandman carries a lot of specialty stuff.
[cctalk] Re: Z80 vs other microprocessors of the time.
On 4/22/24 14:09, Bill Gunshannon via cctalk wrote: Would it not be possible to use something like a Blue Pill to make a small board (small enough to actually fit in the CPU socket) that emulated these old CPUs? Definitely enough horse power just wondered if there was enough room for the microcode. Microcore Labs has done this using a Teensy plus a small adapter board; see https://microcorelabs.wordpress.com/2022/05/11/mclz8-zilog-z80-emulator-in-trs-80-model-iii/ (Github repo: https://github.com/MicroCoreLabs/Projects/tree/master/MCLZ8 ). There are others there as well.
[cctalk] Re: Z80 vs other microprocessors of the time.
On 4/22/24 12:18, Chuck Guzis via cctalk wrote: I don't know if this applies to the Z80, but on the 8080, 16-bit increment/decrement is handled by a separate increment block (also used to advance the P-counter and stack operations). Probably one of the reasons that INX/DCX doesn't set any flags. 16-bit INC and DEC are indeed handled by a separate block, which also gets used to increment PC and decrement SP at the appropriate times. Ken's page on the 4-bit ALU has a 'mapped' dieshot showing it. Ken covers it operation in the blog article https://www.righto.com/2013/11/the-z-80s-16-bit-incrementdecrement.html
[cctalk] Re: Z80 vs other microprocessors of the time.
On 4/21/24 20:06, Peter Coghlan via cctalk wrote: Why is that? Did the Z80 take more cycles to implement it's more complex instructions? Is this an early example of RISC vs CISC? Z80 is blessed with a 4-bit ALU, verified by reverse engineering dieshots ( https://www.righto.com/2013/09/the-z-80-has-4-bit-alu-heres-how-it.html ). Die real estate forced the design to do without a full 8-bit ALU. When you have a 4-bit ALU, and you are doing 16-bit math, you will need 4 cycles through the ALU. Neither 6502 nor Z80 are RISC. 6502 simply runs very efficiently thanks to the design decisions made; 8 bit ALU, 8 bit registers for everything, including stack. Math is fast. Biphase clocking allows what could be considered a precursor of double-data-rate designs. The Visual6502 project shows the 'tick-tock' of it very well. If you want to see what can be done with sufficient real estate on the chip and using more modern design methodologies, pick up a copy of Monte Dalrymple's book "Microprocessor Design using Verilog HDL' ( https://www.elektor.com/products/microprocessor-design-using-verilog-hdl-e-book )in either ebook or paperback form (I bought both); Monte was responsible for Z380 among other designs, and they are very efficient. Today's eZ80 builds on that, and is as efficient as the 6502 and much, much faster. There are many softcores out there, so Z80 lives on in both those as well as the Z180 (several parts are EoL (either last-time-buy or obsolete) but some parts are still Active) and the eZ80 (most instructions on eZ80 are single-cycle, and the chip is pipelined; eZ80 has a 24-bit ALU; plus, eZ80 is a very capable microcontroller). The Z84015, in both 6 and 10MHz variants, still shows as Active at Digikey. ALL are of course surface mount. Through-hole anything is a dying breed. The Z80 is dead; long live the Z80.
Re: TRS-80 Model IV PALs
On 12/5/19 12:39 PM, Eric Smith via cctalk wrote: Last year I read most of the PALs and HALs of a TRS-80 Model 16B main board (same as Model 12 main board). I was surprised that none of the PALs were protected, and even more surprised that some (but not all) of the HALs could be read as PALs. Eric, first, I want to thank you for the excellent M2 ROM disassembly you did; while I was helping debug the MAME trs80m2 emulator your listing was extremely helpful in tracing down the problem which single-stepping in the MAME debugger (it was a bug in the WD1791 emulation of deleted data address marks). Second, there is a published European patent on the Model 4 circuitry; see http://www.freepatentsonline.com/EP0126305.pdf for the details. The PAL equations and pinouts begin on PDF page 31. The 12/16B/6000 mainboard's PAL equations are printed in the service manuals for those machines; the 6000 service manual is available on archive.org. But it is a bit surprising that the security fuse wasn't blown; Jerry Ballard and Frank Durda were both unsure (years ago when I asked them both) if the M4's PALs had the security fuse blown or not, and at that time I didn't have the equipment to try to read them.
Re: P112
On 11/29/19 7:01 PM, Bill Gunshannon via cctalk wrote: Let's try again with the right name in the Subject line! It's not really classic (although it does try to pretend to be but does anyone here do anything with the P112 SBC? I am trying to get 8" disks running on it but I am seeing some rather strange behavior. Well, the P112 is a classic of sorts, being a mid-1990's design (much like the CPU280 from Tilmann Reh that I 'revived' a couple of years back, and still have PCBs leftover :-) ). The P112 kit was, up until a few months ago, still available from David Griffith (661.org, which you've already found). I bought two while I was buying a few years back, and built up one of them, which I still use a bit with a GIDE from Terry. I am actually planning to port the TRS-80 Model 4's LS-DOS 6 to it for fun, but haven't had time to work too much with it. I was actually thinking about fabbing a few boards to try out faster Z80182 chips (officially there is a 33MHz version that has been overclocked by some to well over that speed) rather than risk desoldering the 16MHz '182 from one of the two kit boards I bought, so, for David Griffith's benefit, I would be interested in a bare board or three myself if he decides to fab some. Sourcing the SuperIO and doing the fine-pitch SMD soldering will be a bit of a challenge, but worth it I believe. As far as 8-inch drives are concerned, you would need to do exactly everything you would need to do to hook up an 8-inch drive to a PC, since the P112 uses a PC SuperIO chip for the FDC, and the floppy headers have PC pinouts and signal meanings (unlike the CPU280.). The dBit FDADAP or similar would be needed to generate TG43 as well as translate the pinout correctly. I haven't tried single-density support on the P112, so don't know if that would work or not, but the SuperIO chip used should be able to do that.
