dp1g+@andrew.cmu.edu (Demetri Patukas) (05/08/88)
I have a Model 4P with a bad ram chip.
After swapping some chips around I found the offending chip.
So I thought, "no problem, just stick in a 4164 and off we go"
Didn't work.
So... can anyone tell me what the story is on the ram chips in the 4P?
They have the number "8040665" stamped on them with both Motorola and
Tandy logos. I have a friend who used to do upgrades on these who
claims that these should be the same as 4164's, but when I used a 4164
it always read zero in that bit position. Are these special Tandy
rams? Can I maybe bend some pins and use a 4164?
Also, although my machine has sockets for a second set of 64K, my
friend tells me that I will need a new PAL chip to get the machine to
recognize it. Where can I get the new PAL? How much should I expect
to pay?
demetri patukas internet: dp1g+ @ andrew.cmu.eduuhclem@trsvax.UUCP (05/10/88)
<> B>I have a Model 4P with a bad ram chip. B>After swapping some chips around I found the offending chip. B>So I thought, "no problem, just stick in a 4164 and off we go" Didn't work. B>So... can anyone tell me what the story is on the ram chips in the 4P? B>They have the number "8040665" stamped on them with both Motorola and B>Tandy logos. I have a friend who used to do upgrades on these who B>claims that these should be the same as 4164's, but when I used a 4164 B>it always read zero in that bit position. Are these special Tandy B>rams? Can I maybe bend some pins and use a 4164? The 8040665 is a 200nsec 64K x 1 dynamic RAM. It has the standard pinout. Most likely, the part you tried to use was slower, or possibly it was a TI DRAM. For some reason, I have never seen a Z80-based system that would work well (or sometimes at all) with TI DRAM's. (I assume the part you tried was good.) Find yourself a chip by Motorola, Mostek or some other manufacturer. Right now, 150nsec's are usually cheaper than 200's (more people making them), so check the cost of 150's. (The Tandy part number 8041665 is a 150nsec part.) You can perform a primitive memory test by holding down the period (.) key then pressing RESET on the Model 4P. Note that this only tests the upper 48K of the first 64K. If the problem persists, swap the RAM in the fault position with one in a position that shows no problems. If the faulty bit or bits move, then one of those two chips is faulty. If the problem remains in the same place, you may be replacing the wrong RAM chip. If a range of bits is persistently bad, you may have a faulty chip socket or a damaged etch. B>Also, although my machine has sockets for a second set of 64K, my B>friend tells me that I will need a new PAL chip to get the machine to B>recognize it. Where can I get the new PAL? How much should I expect B>to pay? Only the Model 4 (not 4D or 4P) requires a PAL change. On the Model 4P, the RAM goes in U153-U160 (both board types). Then if you have a gate-array 4P board, move E2-E3 to E1-E2 for 128K. If you have the non-gate-array 4P move E12-E13 to E11-E12 for 128K. (The gate-array board can be identified by looking at the larger chips (>24 pins) for parts marked "4.1", "4.2" and "4.3". Only the gate array board has these parts.) After booting LS-DOS 6.3/TRSDOS 6.x, type: MEMORY (A=X'0200') and if the value displayed is 0xF8, LS-DOS sees 128K. <This information is provided by an individual and is not nor should be construed as being provided by Radio Shack or Tandy Corp. Radio Shack/Tandy Corp has no obligation to support the information provided in any way.> "Thank you, Uh Clem." Frank Durda IV @ <trsvax!uhclem> ...decvax!microsoft!trsvax!uhclem ...convex!infoswx!hal6000!trsvax!uhclem ...sys1!hal6000!trsvax!uhclem "What else is there to say when there is nothing to say I always say..."
karl@ddsw1.UUCP (Karl Denninger) (05/10/88)
In article <4WUwM8y00XcSQ5LUE3@andrew.cmu.edu> dp1g+@andrew.cmu.edu (Demetri Patukas) writes: > >I have a Model 4P with a bad ram chip. > >After swapping some chips around I found the offending chip. > >So I thought, "no problem, just stick in a 4164 and off we go" > >Didn't work. > >So... can anyone tell me what the story is on the ram chips in the 4P? >They have the number "8040665" stamped on them with both Motorola and >Tandy logos. I have a friend who used to do upgrades on these who >claims that these should be the same as 4164's, but when I used a 4164 >it always read zero in that bit position. Are these special Tandy >rams? Can I maybe bend some pins and use a 4164? You can use a 4164 IF AND ONLY IF the refesh cycle spec is right. The scoop is this -- some chips require 128 "refresh" cycles, and some require "256". The latter chips do NOT work in Model IVs. This includes nearly ALL of the American parts -- only the Jap stuff works at all. An example of "Known good": Oki 4164 Texas Instruments 4164's, for example, while having the same part number (4164) do not work at all. >Also, although my machine has sockets for a second set of 64K, my >friend tells me that I will need a new PAL chip to get the machine to >recognize it. Where can I get the new PAL? How much should I expect >to pay? If your Model IV is an older model (which tube, non-clustered arrows) then you need the PAL for the second 64K. Good luck finding one now-a-days... If it's a new one (green w/cluster) then you only need to solder a wire or two and put in the chips. Somewhere I may still have the info around -- we used to do these on a regular basis. --- Karl Denninger | Data: +1 312 566-8912 Macro Computer Solutions, Inc. | Voice: +1 312 566-8910 ...ihnp4!ddsw1!karl | "Quality solutions for work or play"