Pentagon FAQ (Frequently Asked Questions) v1.0.2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Q. What is Pentagon ? A. Pentagon is Soviet clone of Sinclair Zx-Spectrum. The first version of this machine was released in Moscow in 1989. It was small 48k machine with built-in Beta 128 disk interface. Lately in 1990 was released an improved version with 128k memory and Zx-Lprint MKIII printer interfaces added. There are at least four different versions of Pentagon: a) Pentagon 48k b) Pentagon 128k without AY (or YM) sound chip (version 1) c) Pentagon 128k with AY (or YM) sound chip (version 2) d) Pentagon 128K with AY (or YM) sound chip (version 2+) The last of them (2+) seems to have different video-frame timing. I have also heard of version 3, but I have never seen this one and can't confirm rumours about it. Q. Why Pentagon has so strange name ? A. This name was given to 48k version because of ground track layout on printed circuit board. This is reminds geometrical figure called pentagon. Pentagon 128k has another ground track layout. Q. I've heard it is Super-Spectrum, what are features of this clone ? A. This is not Super-Spectrum, just clone which has some ideas which were not used by Sir Clive Sinclair (why ???). I'll be talking about 128k version only because it is very difficult to find 48k one now and there are no much differences anyway (just more memory, sound chip and Zx-Lprint MKIII printer interface added to Pentagon 128k). a) 128k of NOT-CONTENDED memory (no slow areas). b) Z80 works at 3.5MHz (there are 14MHz crystall and 14E6/4=3.5E5). c) Built-in Beta 128 disk interface (originally developed by Technology Research Ltd in UK and rebuilt in Soviet Union in 1988) with Tr-Dos operating system on EPROM chip. Tr-Dos option added to main menu of original 128k EPROM. d) Built-in Zx-Lprint MKIII printer interface (has its own 2k ROM). e) Reading from non-existand port (like 0xFF) will never give you current screen attribute (same as on original +2A, +2B and +3 Speccy models). f) There was no AY sound chip layouted on the first version of 128k model but it is easy to add this thing - remove Z80 from its socket, insert small "Sound-chip board" to place of Z80 and plug Z80 CPU into special socket on that board. Or you can just solder some wires directly to Z80 CPU pins or Pentagon board tracks. The second version of Pentagon has sound chip layouted on board, but there is no tape port. Actually most people use YM2149 sound chip instead of AY because of better sound (it is pin and functionally compatibility to GI-AY-3-8912/10 sound chip). g) There are 71680 t-states per each video frame. Each video frame has 320 lines, and each line has 224 t-states. Also the upper border has 80 (!) lines but first 16 of them are not shown on the screen. So its possible to change border colour for a short time then change it back and nobody note that. h) Pentagon uses same simplified address decoding scheme as original 48k, 48k+, 128+ models used (you can use 0xFD port to have access to 128k memory pages management and to sound chip registers). i) Pentagon has no original edge connector, but as far as there are no ULA every wire can be soldered directly to Pentagon board. j) Version 2 has Kempston joystick right on the board, version 1 usually have this thing on additional "Sound-chip board". Q. What did they used instead of original ULA ? A. In Pentagons used about 20 ICs to "emulate" original ULA chip. ULA of 128+ has been completely cracked in beginning of 1987 and first Soviet clones of 128+ started to appear in shops. Q. I've heard there are Beta 128 disk interface has been built in Pentagon. As I see this isn't the best disk interface, so why they made it ? A. First of all they didn't MADE it, they just CRACKED original Beta 128 by Technology Research Ltd which was released in UK in 1986. In 1987 it was imported to Soviet Union by some people (I think this happened because price was about just 70UKP per unit) and in the middle of 1988 circuit diagram of cracked and remade on Soviet ICs interface became publicaly available. Q. Some people say there are 512k and 1024k versions of Pentagon available and also many strange modifications (like 512x192x2, 32x192x16, shadow RAM, HD disks support, etc). How it added and how many software support such features ? A. There are nothing difficult in adding such things to Pentagon (e.g. that 32x192x16 can be made in 5 (!) minutes just with THREE short wires and ONE switcher). Of course you must know which end of soldering iron to hold in a hand, if you don't know that you can easily find a right end of the soldering iron after little experiment. 512k used in many programs (disk commanders, disk copiers, assemblers, debuggers, e-magz, games, etc). The 1024k memory expansion can be used as ~880k (!) RAM disk right from Tr-Dos (as drive D or E). The contents of RAM disk will not be cleared by normal reset routine of 128k ROM, so this is more like RAD disk of Amiga. That 512x192x2 (or even 512x384 in lace with using two video RAM pages) used in text editors and FIDO/Internet mail programs. Version 2.41c of BGE (it is new very good gfx editor) already has support for new 128-colours mode, which replaced standard FLASH signal. Have you seen _many_ programs what use that FLASH ? I've not. Very probably other new gfx editors (such as ArtWorks, Excess de luxe Paint, GFX Station) may have support for such modes added in next versions. Q. How much programs were converted to work with Beta 128 interface ? A. Believe or not, but for many years of work we've probably converted every single Zx-Spectrum game we had to work with Beta 128 disk interface. And every new program (game or system one) released in ExUSSR will be Beta 128 only. Please, do not think that we release Beta 128 only versions because we want to make conversion from Beta 128 to other disk system harder! We only want to have our programs load faster (TRDOS v5.xx is very old thing and has useless delays in code). Nobody uses tapes here (well maybe only those who cracks original games). And, if you want to see our new programs working on your disk system, why you don't explain us how it should be implemented ? Q. Is it possible to buy such thing ? A. Yes, but now it is possible to find used boards only. But if there will be at least 10-15 orders I'll try find and re-launch a plant. Q. How many boards in Pentagon and how big is it ? A. Pentagon has SINGLE board of 135mm x 310mm x 10mm (+20mm in case of additional AY interface board in version 1). Q. How does complete Pentagon looks like ? A. Pentagon was sold in two or three standard cases. First of them was grey plastic desktop which may have up to two 5.25" disk drives (or 3.5" disk drives installed into special 5.25" expanders) inside. There are enought place for drives, PSU, Pentagon board and for several add-ons, with small external grey plastic case for keyboard. Second was white metallic "mini tower" casing with place for two 5.25" disk drives (installed vertically). Inside it split into two parts, one part for Pentagon board, another one for PSU and disk drives. As long as this is mettalic case it can suppress noice, but does it not as good as you may expect. And third case is "single drive" version of case of second type. Both second and third cases has white external metallic cases for keyboard. If you bought not complete Pentagon, but board only, you may put it anywhere you like, even into a desk drawer of needed size. Same may be done with any other clone. Q. What kind of keyboard should be used with Pentagon ? A. Standard keyboard which can be used with Zx-Spectrum+ and Zx-Spectrum 128+ (I mean same keyboard layout and same ribbon connectors pinout). The only difference between Pentagon keyboard and say Speccy +2 keyboard is that ribbon connectors are located on the long side of keyboard instead of the short one. Q. Why people from ExUSSR use to say "TRDOS" instead of "Beta 128" ? A. Probably because here is no any other disk interfaces and many clones (and Pentagon is one of them) have Beta 128 built-in to computer board. The only difference we've is Tr-Dos versions. So people use to say "TRDOS" also because anybody can program any other DOS to the Beta 128 EPROM chip (like NEOS, IS-Dos, etc). Q. Do you use "QAFZYI3" keyboard layout with Pentagon in Ex Soviet Union ? A. No! There is normal US keyboard layout but with small red, green or black cyrillic letters added to the free space in right bottom corner of button. Q. I heard that all Pentagons were hand made, is it true ? And how much boards was sold ? A. Well, not all. But about half of them actually. All Pentagon boards I'd seen (except one) were soldered on plants. I knew many people who used to trade Pentagon boards and most of them worked on electronic plants and they definitely had access to programmable soldering stations. It was easy to use such stations for your own purposes after end of business day. Till time when security grab you and throw away because it is too late and you have to go home ;) I can't say how much boards was sold I only know there was about 3E6 Speccy users in 1992 and this number increased very quickly. Q. Why most of scene demos from Russia were timed for Pentagon only ? A. Probably every demo maker was Pentagon owner. This why most of demos from ExUSSR timed for this machine only, well and most of them had contacts to Speccy users with Pentagons only, so why think about others if "nobody" of them have something other ? Another reason - Pentagon has no contended memory areas, so this is nice thing for demo makers. Q. Can I use General Sound (4x8-bit sound channels) card with Pentagon ? A. Of course you can. Q. Pentagon is just a clone and I think there are programs which does not work at all or does not work properly. How much of such programs are there ? A. I know about 10 titles which refused work on Pentagon. They required 0xFF port. Yes, I said what I wanted to say - they REQUIRED. All such programs were fixed for Pentagon. And about incorrectly working ones - its mainly demos timed for original Speccy models. Part of such programs was fixes, but if you can not find fixed version you can do another hardware fix for your Pentagon - "a la original INT" (just one IC) and you'll see at least something. Q. After reading the "Russian Spectrm Machines FAQ" I am started to think that Pentagon boards were not very good quality and required to be repaired most of time. Is this true ? A. Hard to say, this all depends. I'm using my Pentagon 128 v1 with YM sound chip since 1991 and it was broken just ONE time when I dropped screw into case of working Pentagon. Shall I say Pentagon didn't liked that ? Please do not trust to such words, there are a 'resistance' between owners of Scorpion and owners other clones (Pentagon, Profi, ATM, etc). Scorpion owners like to say that their machine is 100% compatible to original machine (VERY far from the truth), but they do not know what they are talking about, because 99.9% of them NEVER seen any original model. Q. But I still think... A. Yes, it is useful to think about something sometimes... Q. One man said Pentagon has one unused page in ROM chip, what did he ment ? A. He ment that there are 27512 EPROM chip was used in Pentagon and page number 0 of this chip was empty. With adding one IC and one switcher, writting something to that page (there was BASIC "TURBO 90" used very often) you can switch to another ROM version at any time (even when loaded program is working). Or you can write a commander in that page, there are several ROM versions of file commanders available (e.g. Quick Commander, Real Commander, and others). Q. I do not believe Pentagon has no disadvantages! A. Ghm... Sure it has some. For example, Pentagon has no edge connector and if you do not know how to use soldering iron, then you'll not be able to connect add-ons (sound cards, mouse controller, modems, etc). Also you may see an additional "bright black" colour what should not be displayed. And you can not remove Beta 128 disk interface and install another one. Q. What type of floppy disk drive may be used with Pentagon ? A. You may use vitually any 5.25" or 3.5" double density floppy drives if it has standard 34-pin connector. Pentagon with Beta 128HD may also use any high density floppy drive. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~[End of Pentagon FAQ]~~ Last changed: 09-Feb-2001 (c) 1999...2001 Mac Buster^Extreme Entertainment ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~