February/March 1980, Issue 6

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Nascom 2 RAM board construction notes

page 5 It is reported that certain boards harbour an etching fault whereby the decoupling capacitor for IC8 fails to connect with the ground rail. It is reasonable to check for this fault and to correct it if possible, although its consequences are unlikely to be noticeable and are nothing to do with ‘memory plague’.
page 12 et seq   The memory test programs are written for the T2 monitor and will not operate under Nas-sys 1. It is recommended that the advice given on page 15 is followed and that a small test program is written to test for ‘plague’ only if this condition is suspected. The printed test programs are not specifically designed to reveal plague.” (And probably won’t. Ed.)

(Editors note: We do not like these unspecified references to ‘memory plague’ as unsuspecting purchasers of Nascom 2s would have no idea what is meant; only hardened Nascom 1 owners who read these newsletters will be in the know. For new Nascom 2 owners, ‘memory plague’ is a condition which arises in some memories due to noise and speed problems, and leads to unreliable memory performance (not to be confused with suspect chips). Several notes have been published about ‘memory plague’, and we hope to collect them all together and publish a compendium of memory mods in the next issue. Memory plague may be detected in a Nascom 2 by the failure of the Basic to initialize properly, or the ‘free memory’ message giving silly or inconsistent answers after initialization. This is not the same as the total failure of the Basic to initialize if the memory construction notes are followed to the letter (having missed the small errata); where the constructor is instructed to connect decode pad 12 to P5, thus enabling the RAM board EPROM block to page F, thereby totally disabling half of the Basic.)

“8K Basic programming manual

page 16 The list of reserved words should include DEEK and MONITOR.
page 24 The second sentence should read: ‘It uses locations 1000H to 113EH (4414) ....... .’ The second sentence should read: “Locations 113FH to DFFFH are therefore ....... .’”

(Editors note: Well thats what it said, and we couldn’t understand it either, so we looked it up in a manual that was a couple of months old. That didn’t make sense either, suggesting that the Basic used 8K+ of workspace, so after a little investigation we think page 24 should read as follows:

“Nascom Basic leaves locations between 0C80H (3200 decimal) and 0FFFH (4095 decimal) inclusive for use by user machine code routines. It uses locations 1000H (4096) to 10F9H (4345) inclusive for workspace and resides in E000H (-8192) to FFFFH (-1) inclusive. Locations 10FAH (4346) to DFFFH (-8193) inclusive are therfore available for the users’ Basic program and data.”)

“page 26 program 1 line 40: the word ‘to’ should be in upper case.”

For a manual the size of the Nascom 2 manual you must expect a few mistakes but we bet they haven’t all been found (we haven’t tried looking yet), but if you come across any please let us know. so that they can be ammended in later manuals. That way new users of Nascom 2 might not run into some of the problems that have been experienced.

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