Oh Yes… Oh NO!!
It’s apparently true that Timex Portugal is going to bring back the TS 2068 as the Timex 2068. They have the 3″ floppy drives for it too. That’s just grand. Unfortunately, it will have a Spectrum backplane which may make them incompatible with some of the US TS 2068 peripherals. It will come with a Spectrum ROM cartridge though. I’m glad that Timex is such a considerate company. (The disk drives will be available for both types of 2068’s.) Will the Timex disk I/F be 2068, Spectrum AND CPM compatible?
They are keeping they buggy ROM and useless joysticks and giving up the 1000 compatible expansion port. How about a couple of Kempston compatible joystick ports built in. Come on guys, let’s get creative!
Timex has a tremendous public relations task at hand. We do want to see 2068 computers brought back, but not in bits and pieces. I pose a question to all of you.
Would you prefer to see Timex sell the 2068, or would you like to see Sir Clive get the North American rights back and come in with the Spectrum+? Do we need another half-breed unsupported computer in this country? I’m sorry but that’s the way I feel.
Oh No… Oh YES!!
Well, let’s get back to Timex again. Fred Nachbaur came to visit in April and together we discovered a VERY serious bug in the TS1500. They (Timex) changed very little code from the 1000, but they really screwed up what they did change (probably practicing for the 2068). It is documented that on power up, the location at 2000h (8192) is tested for a cartridge. It is decremented (if you use a Hunter board or other ram there, watch out). If the result is zero, then you JUMP to 2000h and proceed. That was bad enough! In the course of writing that inane bit of code, they screwed up the LOAD routine and they DID NOT fix it. On a bad load, you will jump to the byte after LD HL, RAMTOP (into the middle of it) in the NEW routine. Consequently, the stack pointer will be placed at the memory location where the bad load occured. Ramtop will not appear to change. If you are lucky, when the screen clears you will return to 0000h and start fresh. If you are not (e.g., you loaded almost to the end of the program), then on the next load you will crash again. We will have the full report for this and all those other “bugs” in the next issue, when we give you lots of things to do with your eprom programmer.
Oh Well
Dear Editor, I just received 2/4. It looks great, but you forgot a couple of things and made a few mistakes.
1. You didn’t mention that an expansion board is needed on the 2068 for the programmer, but say that it is needed on the 1000(?)
2. You referred to that extra gate (decoding the EXROM) last time saying it would be used in the next issue, but you left it out along with the 2068 ROM changes.
3. And those pullup resistors! I’m glad you didn’t put my name on that one. You are wrong! You added 7 pullups when 8 are required. (Don’t you like D2?) This will find its way into other publications and everybody will be wrong. The pullups supply the low order address for IM2 (there is a lot of software like this) driven software…. The keyboard is not one of the things that these help. Also the issue 1 Spectrum put an FFh on the bus, not the Issue 3 (puts out a BFh)
John Oliger
Dear John, I stand corrected on the keyboard point (but now you know why I bend your ear on the phone so much). Even worse than splitting the programmer article into two, the Cassette Connection got bumped. I referred to that in the first paragraph on page 1. If you solder an edge connector on the programmer, then you do not need an expansion board (although it is preferred). You need a mother board on the 1000 due to the width of the board. The 2068 schematic shows D2 with a 10K pullup on it, just right of U16. Well, I retract your name from the list of associated people. I promise to take better notes next time. (See Support for more information.)
Pro/File 2068 Books are Shipped
Tom woods informs me that all Profile 2068 manuals have been shipped. If you didn’t get one or you would like to get one, then get in touch with him directly.
Q/A
Dear Editor, I am writing to enlist your help. I recently bought an A and J Microdisk. I like the unit well enough, but I have run into a small problem. I have Bill Russell’s Romswitch and found that I cannot SAVE or LOAD Spectrum programs to the Microdisk. Can you shed any light on this?
Ken Duda
[address omitted]
[phone number omitted]
You have run into a big problem. The A&J system uses the EXROM for various purposes. The Spectrum part of the Romswitch will work even if you plug the EXROM in backwards. I won’t even mention that the routines in each of the ROMs are in different locations. It will be necessary to copy the operating system into RAM and convert all the addresses that make specific ROM calls. It may require relocating the the A&J code to a high memory location and let it reside there. It’s a big job! If anyone made this change or is contemplating it, please get in touch with Ken. He’d like to talk to you.
Spectrumizing
Spectrum ROMs are available from many sources. There are three methods for installation. You can plug in a ROM directly, use a cartridge board or install a switch unit. Check with your nearest dealer or get in touch with the following people:
Romswitch- G. Russell Electronics, PO Box 539, Centre Hall, PA 16828, (814) 364-1325
Cartridge board- Doug Dewey, 206 James St., Carrboro, NC 27510
ROM- English Micro Connection, 15 Kilburn Ct., Newport, RI 02840, (401) 849-3805 Write for more information.
BUG ALERT!
The last three bytes were omitted from the decimal listing of “CLEAR THAT SCREEN” in Vol. 2:4. These bytes are: 245, 008, 201.
VOLUME 1 book, page 62: In Figure 2b, pin 3 of the top LM311 should be labelled “Sync Ref.” (reference), not “Sync Ret.” Also, the resistor from ULA pin 16 to ground was not labelled; this part is 10Kohm.
VOLUME 1, Page 91: The last paragraph was chopped off in the middle; it should have been chopped entirely. Page 94, column 2: The least square equation for a linear fit should have the quantity on the right (Y(calc.) – Y(i)) SQUARED. Similarly, the summations in the equations in the following paragraph should be squared.
Volume 1, Page 96:
F''(X) = -SINE(X/57.29)/57.29**2
F'''(X) = -COS(X/57.29)/57.29**3
F''''(X) = SINE(X/57.29)/57.29**4Busted Chips
It has come to my attention that Timex no longer has parts for the 1000 computers, although they will fix your computer for a fee. Sinclair Research, 50 Staniford St., Boston, MA 02114, will supply ZX-81 parts. There are other suppliers for these parts (see Support 2/3, 2/4) also.
In a conversation with a knowledgeable indivdual at Timex, it was pointed out that the 2068 SCLD chip is no longer being made (NCR made it originally). In other words, when it goes, so goes your computer. However, it was also pointed out that it is difficult to “blow it” unless you really try. One problem that has come up is that the modem hook up may give you grief. This problem occurs when switching power supplies on and off in the wrong order. Although your computer may go down, it is not out. Since you can no longer send it back to Timex for repair, replace the two 74LS245 buffer chips (about $4.00) and get back on line again.
Since 2068 computers are being made in Portugal and sold in Europe, I’m pretty sure that the SCLD chip is still being made. The source for these should not dry up too quickly. I’m glad that we can always get straight answers from “Mother Time.”